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  • 1.
    Yuan, Fanglong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Beijing Normal Univ, Peoples R China.
    Folpini, Giulia
    Ist Italiano Tecnol, Italy.
    Liu, Tianjun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Singh, Utkarsh
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Treglia, Antonella
    Ist Italiano Tecnol, Italy; Politecn Milan, Italy.
    Lim, Jia Wei Melvin
    Nanyang Technol Univ, Singapore.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergei I.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Sum, Tze Chien
    Nanyang Technol Univ, Singapore.
    Petrozza, Annamaria
    Ist Italiano Tecnol, Italy.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Bright and stable near-infrared lead-free perovskite light-emitting diodes2024In: Nature Photonics, ISSN 1749-4885, E-ISSN 1749-4893Article in journal (Refereed)
    Abstract [en]

    Long-wavelength near-infrared light-emitting diodes (NIR LEDs) with peak emission wavelengths beyond 900 nm are of critical importance for various applications including night vision, biomedical imaging, sensing and optical communications. However, the low radiance and poor operational stability of state-of-the-art long-wavelength NIR LEDs based on soft materials remain the most critical factors limiting their practical applications. Here we develop NIR LEDs emitting beyond 900 nm with improved performance through the rational manipulation of p doping in all-inorganic tin perovskites (CsSnI3) by retarding and controlling the crystallization process of perovskite precursors in tin-rich conditions. The resulting NIR LEDs exhibit a peak emission wavelength at 948 nm, high radiance of 226 W sr-1 m-2 and long operational half-lifetime of 39.5 h at a high constant current density of 100 mA cm-2. Our demonstration of efficient and stable NIR LEDs operating at high current densities may also open up new opportunities towards electrically pumped lasers. Controlling the intrinsic doping of lead-free perovskites enables near-infrared LEDs emitting at 948 nm with a peak radiance of 226 W sr-1 m-2 and a half-lifetime of 39.5 h.

  • 2.
    Zarshenas, Mohammad
    et al.
    Fraunhofer Inst Mech Mat IWM, Germany; Univ Freiburg, Germany.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Sarakinos, Kostas
    Univ Helsinki, Finland; KTH Royal Inst Technol, Sweden.
    Diffusion and magnetization of metal adatoms on single-layer molybdenum disulfide at elevated temperatures2024In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 42, no 2, article id 023409Article in journal (Refereed)
    Abstract [en]

    The present work models temperature-dependent ( 500-1300K) diffusion dynamics of Ag, Au, and Cu adatoms on MoS2 as well as electronic and magnetic properties of adatom (Ag, Au, and Cu)/MoS2 systems. Modeling is done by means of ab initio molecular dynamics (AIMD) simulations that account for van der Waals corrections and electronic spin degrees of freedom in the framework of density functional theory. It is found that Ag and Au adatoms exhibit super-diffusive motion on MoS2 at all temperatures, while Cu adatoms follow a random walk pattern of uncorrelated surface jumps. The observed behavior is consistent with AIMD-calculated effective migration barriers Ea ( EaAg=190 +/- 50meV, EaAu=67 +/- 7meV, and EaCu=300 +/- 100meV) and can be understood on the basis of the considerably flatter potential energy landscapes encountered by Ag and Au adatoms on the MoS2 surface (corrugation of the order of tens of meV), as compared to Cu adatoms (corrugation >100meV). Moreover, evaluation of the electronic and magnetic properties of AIMD configurations suggest that Ag, Au, and Cu monomer adsorption induces semimetallic features in at least one spin channel of the adatom/MoS2 electronic structure at elevated temperatures. The overall results presented herein may provide insights into fabricating 2D-material-based heterostructure devices beyond graphene

  • 3.
    Liang, Akun
    et al.
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Osmond, Israel
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Krach, Georg
    Univ Munich LMU, Germany.
    Shi, Lan-Ting
    Spallat Neutron Source Sci Ctr, Peoples R China.
    Bruening, Lukas
    Univ Cologne, Germany.
    Ranieri, Umbertoluca
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Spender, James
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Massani, Bernhard
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Stevens, Callum R.
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    McWilliams, Ryan Stewart
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Bright, Eleanor Lawrence
    European Synchrotron Radiat Facil, France.
    Giordano, Nico
    Photon Sci, Germany.
    Gallego-Parra, Samuel
    European Synchrotron Radiat Facil, France.
    Yin, Yuqing
    Univ Bayreuth, Germany.
    Aslandukov, Andrey
    Univ Bayreuth, Germany.
    Akbar, Fariia Iasmin
    Univ Bayreuth, Germany.
    Gregoryanz, Eugene
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland; Ctr High Pressure Sci & Technol Adv Res, Peoples R China; Inst Solid State Phys, Peoples R China.
    Huxley, Andrew
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Pena-Alvarez, Miriam
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Si, Jian-Guo
    Spallat Neutron Source Sci Ctr, Peoples R China.
    Schnick, Wolfgang
    Univ Munich LMU, Germany.
    Bykov, Maxim
    Univ Cologne, Germany; Goethe Univ Frankfurt, Germany.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Laniel, Dominique
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    High-Pressure Synthesis of Ultra-Incompressible, Hard and Superconducting Tungsten Nitrides2024In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028Article in journal (Refereed)
    Abstract [en]

    Transition metal nitrides, particularly those of 5d metals, are known for their outstanding properties, often relevant for industrial applications. Among these metal elements, tungsten is especially attractive given its low cost. In this high-pressure investigation of the W-N system, two novel ultra-incompressible tungsten nitride superconductors, namely W2N3 and W3N5, are successfully synthesized at 35 and 56 GPa, respectively, through a direct reaction between N2 and W in laser-heated diamond anvil cells. Their crystal structure is determined using synchrotron single-crystal X-ray diffraction. While the W2N3 solid's sole constituting nitrogen species are N3- units, W3N5 features both discrete N3- as well as N24- pernitride anions. The bulk modulus of W2N3 and W3N5 is experimentally determined to be 380(3) and 406(7) GPa, and their ultra-incompressible behavior is rationalized by their constituting WN7 polyhedra and their linkages. Importantly, both W2N3 and W3N5 are recoverable to ambient conditions and stable in air. Density functional theory calculations reveal W2N3 and W3N5 to have a Vickers hardness of 30 and 34 GPa, and superconducting transition temperatures at ambient pressure (50 GPa) of 11.6 K (9.8 K) and 9.4 K (7.2 K), respectively. Additionally, transport measurements performed at 50 GPa on W2N3 corroborate with the calculations. Two recoverable tungsten nitrides, namely W2N3 and W3N5, are synthesized using laser-heated diamond anvil cells. Both compounds exhibit a high bulk modulus, hardness, and superconducting transition temperature. image

  • 4.
    Lin, Shuyao
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Tech Univ Wien, Austria.
    Casillas-Trujillo, Luis
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mayrhofer, Paul H.
    Tech Univ Wien, Austria.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Koutna, Nikola
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Tech Univ Wien, Austria.
    Machine-learning potentials for nanoscale simulations of tensile deformation and fracture in ceramics2024In: npj Computational Materials, E-ISSN 2057-3960, Vol. 10, no 1, article id 67Article in journal (Refereed)
    Abstract [en]

    Machine-learning interatomic potentials (MLIPs) offer a powerful avenue for simulations beyond length and timescales of ab initio methods. Their development for investigation of mechanical properties and fracture, however, is far from trivial since extended defects-governing plasticity and crack nucleation in most materials-are too large to be included in the training set. Using TiB2 as a model ceramic material, we propose a training strategy for MLIPs suitable to simulate mechanical response of monocrystals until failure. Our MLIP accurately reproduces ab initio stresses and fracture mechanisms during room-temperature uniaxial tensile deformation of TiB2 at the atomic scale ( approximate to 103 atoms). More realistic tensile tests (low strain rate, Poisson's contraction) at the nanoscale ( approximate to 104-106 atoms) require MLIP up-fitting, i.e., learning from additional ab initio configurations. Consequently, we elucidate trends in theoretical strength, toughness, and crack initiation patterns under different loading directions. As our MLIP is specifically trained to modelling tensile deformation, we discuss its limitations for description of different loading conditions and lattice structures with various Ti/B stoichiometries. Finally, we show that our MLIP training procedure is applicable to diverse ceramic systems. This is demonstrated by developing MLIPs which are subsequently validated by simulations of uniaxial strain and fracture in TaB2, WB2, ReB2, TiN, and Ti2AlB2.

  • 5.
    Koutna, Nikola
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. TU Wien, Austria.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mayrhofer, Paul H.
    TU Wien, Austria.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Phase stability and mechanical property trends for MAB phases by high-throughput ab initio calculations2024In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 241, article id 112959Article in journal (Refereed)
    Abstract [en]

    MAB phases (MABs) are atomically-thin laminates of ceramic/metallic-like layers, having made a breakthrough in the development of 2D materials. Though offering a vast chemical and phase space, relatively few MABs have been synthesised. To guide experiments, we perform high-throughput ab initio screening of MABs that combine group 4-7 transition metals (M); Al, Si, Ga, Ge, or In (A); and boron (B) focusing on their phase stability trends and mechanical properties. Considering the 1:1:1, 2:1:1, 2:1:2, 3:1:2, 3:1:3, and 3:1:4 M:A:B ratios and 10 phase prototypes, synthesisability of a single-phase compound for each elemental combination is estimated through formation energy spectra of competing dynamically stable MABs. Based on the volumetric proximity of energetically-close phases, we identify systems in which volume-changing deformations may facilitate transformation toughening. Subsequently, chemistry- and phase-structure-related trends in the elastic stiffness and ductility are predicted using elastic-constants-based descriptors. The analysis of directional Cauchy pressures and Young's moduli allows comparing mechanical response parallel and normal to M-B/A layers. The suggested promising MABs include Nb 3 AlB 4 , Cr 2 SiB 2 , Mn 2 SiB 2 or the already synthesised MoAlB.

  • 6.
    Koller, Thaddaeus J.
    et al.
    Univ Munich LMU, Germany.
    Jin, Siyu
    Sichuan Univ, Peoples R China.
    Krol, Viktoria
    Univ Edinburgh, Scotland.
    Ambach, Sebastian J.
    Univ Munich LMU, Germany.
    Ranieri, Umbertoluca
    Univ Edinburgh, Scotland.
    Khandarkhaeva, Saiana
    Univ Bayreuth, Germany.
    Spender, James
    Univ Edinburgh, Scotland.
    McWilliams, Stewart
    Univ Edinburgh, Scotland.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Giordano, Nico
    Deutsch Elektronen-Synchrotron DESY, Germany.
    Poreba, Tomasz
    ID27 High Pressure Beamline, France.
    Mezouar, Mohamed
    ID27 High Pressure Beamline, France.
    Kuang, Xiaoyu
    Sichuan Univ, Peoples R China.
    Lu, Cheng
    China Univ Geosci Wuhan, Peoples R China.
    Dubrovinsky, Leonid
    Univ Bayreuth, Germany.
    Dubrovinskaia, Natalia
    Univ Bayreuth, Germany.
    Hermann, Andreas
    Univ Edinburgh, Scotland.
    Schnick, Wolfgang
    Univ Munich LMU, Germany.
    Laniel, Dominique
    Univ Edinburgh, Scotland.
    Simple Molecules under High-Pressure and High-Temperature Conditions: Synthesis and Characterization of α- and β-C(NH)2 with Fully sp3-Hybridized Carbon2024In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773Article in journal (Refereed)
    Abstract [en]

    The elements hydrogen, carbon, and nitrogen are among the most abundant in the solar system. Still, little is known about the ternary compounds these elements can form under the high-pressure and high-temperature conditions found in the outer planets' interiors. These materials are also of significant research interest since they are predicted to feature many desirable properties such as high thermal conductivity and hardness due to strong covalent bonding networks. In this study, the high-pressure high-temperature reaction behavior of malononitrile H2C(CN)(2), dicyandiamide (H2N)(2)C=NCN, and melamine (C3N3)(NH2)(3) was investigated in laser-heated diamond anvil cells. Two previously unknown compounds, namely alpha-C(NH)(2) and beta-C(NH)(2), have been synthesized and found to have fully sp(3)-hybridized carbon atoms. alpha-C(NH)(2) crystallizes in a distorted beta-cristobalite structure, while beta-C(NH)(2) is built from previously unknown imide-bridged 2,4,6,8,9,10-hexaazaadamantane units, which form two independent interpenetrating diamond-like networks. Their stability domains and compressibility were studied, for which supporting density functional theory calculations were performed.

  • 7.
    Kashiwaya, Shun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Shi, Yuchen
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Synthesis of goldene comprising single-atom layer gold2024In: Nature Synthesis, E-ISSN 2731-0582Article in journal (Refereed)
    Abstract [en]

    The synthesis of monolayer gold has so far been limited to free-standingseveral-atoms-thick layers, or monolayers confned on or inside templates.Here we report the exfoliation of single-atom-thick gold achieved throughwet-chemically etching away Ti3C2 from nanolaminated Ti3AuC2, initiallyformed by substituting Si in Ti3SiC2 with Au. Ti3SiC2 is a renown MAX phase,where M is a transition metal, A is a group A element, and X is C or N. Ourdeveloped synthetic route is by a facile, scalable and hydrofuoric acid-freemethod. The two-dimensional layers are termed goldene. Goldene layerswith roughly 9% lattice contraction compared to bulk gold are observedby electron microscopy. While ab initio molecular dynamics simulationsshow that two-dimensional goldene is inherently stable, experiments showsome curling and agglomeration, which can be mitigated by surfactants.X-ray photoelectron spectroscopy reveals an Au 4f binding energy increaseof 0.88 eV. Prospects for preparing goldene from other non-van der WaalsAu-intercalated phases, including developing etching schemes,are presented.

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  • 8.
    Laniel, Dominique
    et al.
    Centre for Science at Extreme Conditions and School of Physics and Astronomy University of Edinburgh Edinburgh EH9 3FD UK;Material Physics and Technology at Extreme Conditions Laboratory of Crystallography University of Bayreuth 95440 Bayreuth Germany.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Aslandukov, Andrey
    Material Physics and Technology at Extreme Conditions Laboratory of Crystallography University of Bayreuth 95440 Bayreuth Germany;Bayerisches Geoinstitut University of Bayreuth 95440 Bayreuth Germany.
    Khandarkhaeva, Saiana
    Material Physics and Technology at Extreme Conditions Laboratory of Crystallography University of Bayreuth 95440 Bayreuth Germany.
    Fedotenko, Timofey
    Photon Science Deutsches Elektronen‐Synchrotron Notkestrasse 85 22607 Hamburg Germany.
    Yin, Yuqing
    Material Physics and Technology at Extreme Conditions Laboratory of Crystallography University of Bayreuth 95440 Bayreuth Germany;State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China.
    Miyajima, Nobuyoshi
    Bayerisches Geoinstitut University of Bayreuth 95440 Bayreuth Germany.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ponomareva, Alena V.
    Materials Modeling and Development Laboratory NUST “MISIS” Moscow 119049 Russia.
    Jena, Nityasagar
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Akbar, Fariia Iasmin
    Bayerisches Geoinstitut University of Bayreuth 95440 Bayreuth Germany.
    Winkler, Bjoern
    Institut für Geowissenschaften Abteilung Kristallographie Johann Wolfgang Goethe‐Universität Frankfurt Altenhöferallee 1 D‐60438 Frankfurt am Main Germany.
    Néri, Adrien
    Bayerisches Geoinstitut University of Bayreuth 95440 Bayreuth Germany.
    Chariton, Stella
    Center for Advanced Radiation Sources University of Chicago Chicago IL 60637 USA.
    Prakapenka, Vitali
    Center for Advanced Radiation Sources University of Chicago Chicago IL 60637 USA.
    Milman, Victor
    Dassault Systèmes BIOVIA Cambridge CB4 0FJ UK.
    Schnick, Wolfgang
    Department of Chemistry University of Munich (LMU) Butenandtstrasse 5–13 81377 Munich Germany.
    Rudenko, Alexander N.
    Radboud University Institute for Molecules and Materials Heijendaalseweg 135 Nijmegen 6525 AJ The Netherlands.
    Katsnelson, Mikhail I.
    Radboud University Institute for Molecules and Materials Heijendaalseweg 135 Nijmegen 6525 AJ The Netherlands.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Dubrovinsky, Leonid
    Bayerisches Geoinstitut University of Bayreuth 95440 Bayreuth Germany.
    Doubrovinckaia, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Material Physics and Technology at Extreme Conditions Laboratory of Crystallography University of Bayreuth 95440 Bayreuth Germany.
    Synthesis of Ultra‐Incompressible and Recoverable Carbon Nitrides Featuring CN4 Tetrahedra2024In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 36, no 3, article id 2308030Article in journal (Refereed)
    Abstract [en]

    Carbon nitrides featuring three-dimensional frameworks of CN4 tetrahedra are one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, the high-pressure high-temperature synthesis of three carbon-nitrogen compounds, tI14-C3N4, hP126-C3N4, and tI24-CN2, in laser-heated diamond anvil cells, is reported. Their structures are solved and refined using synchrotron single-crystal X-ray diffraction. Physical properties investigations show that these strongly covalently bonded materials, ultra-incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high-pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions.

  • 9.
    Knoop, Florian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Shulumba, Nina
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Castellano, Aloïs
    Université de Liège, Belgium.
    Alvarinhas Batista, J.P.
    Université de Liège, Belgium.
    Farris, Roberta
    Catalan Institute of Nanoscience and Nanotechnology - ICN2 (BIST and CSIC), Spain.
    Verstraete, Matthieu J.
    Université de Liège, Belgium; University of Utrecht, the Netherlands.
    Heine, Matthew
    Department of Physics, Boston College, USA.
    Broido, David
    Department of Physics, Boston College, USA.
    Kim, Dennis S.
    University of California, USA.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial College London, UK.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergei I.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala University, Sweden.
    Hellman, Olle
    Weizmann Institute of Science, Israel.
    TDEP:Temperature Dependent Effective Potentials2024In: Journal of Open Source Software, E-ISSN 2475-9066, Vol. 9, no 94, article id 6150Article in journal (Refereed)
    Abstract [en]

    The Temperature Dependent Effective Potential (TDEP) method is a versatile and efficient approach to include temperature in a binitio materials simulations based on phonon theory. TDEP can be used to describe thermodynamic properties in classical and quantum ensembles, and several response properties ranging from thermal transport to Neutron and Raman spectroscopy. A stable and fast reference implementation is given in the software package of the same name described here. The underlying theoretical framework and foundation is briefly sketched with an emphasis on discerning the conceptual difference between bare and effective phonon theory, in both self-consistent and non-self-consistent formulations. References to numerous applications and more in-depth discussions of the theory are given.

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  • 10.
    Mopoung, Kunpot
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ning, Weihua
    Soochow Univ, Peoples R China.
    Zhang, Muyi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ji, Fuxiang
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Mukhuti, Kingshuk
    Radboud Univ Nijmegen, Netherlands.
    Engelkamp, Hans
    Radboud Univ Nijmegen, Netherlands.
    Christianen, Peter C. M.
    Radboud Univ Nijmegen, Netherlands.
    Singh, Utkarsh
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Understanding Antiferromagnetic Coupling in Lead-Free Halide Double Perovskite Semiconductors2024In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 128, no 12, p. 5313-5320Article in journal (Refereed)
    Abstract [en]

    Solution-processable semiconductors with antiferromagnetic (AFM) order are attractive for future spintronics and information storage technology. Halide perovskites containing magnetic ions have emerged as multifunctional materials, demonstrating a cross-link between structural, optical, electrical, and magnetic properties. However, stable optoelectronic halide perovskites that are antiferromagnetic remain sparse, and the critical design rules to optimize magnetic coupling still must be developed. Here, we combine the complementary magnetometry and electron-spin-resonance experiments, together with first-principles calculations to study the antiferromagnetic coupling in stable Cs-2(Ag:Na)FeCl6 bulk semiconductor alloys grown by the hydrothermal method. We show the importance of nonmagnetic monovalence ions at the B-I site (Na/Ag) in facilitating the superexchange interaction via orbital hybridization, offering the tunability of the Curie-Weiss parameters between -27 and -210 K, with a potential to promote magnetic frustration via alloying the nonmagnetic B-I site (Ag:Na ratio). Combining our experimental evidence with first-principles calculations, we draw a cohesive picture of the material design for B-site-ordered antiferromagnetic halide double perovskites.

  • 11.
    Knoop, Florian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft, Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Scheffler, Matthias
    The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft, Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Carbogno, Christian
    The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft, Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Ab initio Green-Kubo simulations of heat transport in solids: Method and implementation2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 22, article id 224304Article in journal (Refereed)
    Abstract [sv]

    Ab initio Green-Kubo (aiGK) simulations of heat transport in solids allow for assessing lattice thermalconductivity in anharmonic or complex materials from first principles. In this work, we present a detailed accountof their practical application and evaluation with an emphasis on noise reduction and finite-size corrections insemiconductors and insulators. To account for such corrections, we propose strategies in which all necessarynumerical parameters are chosen based on the dynamical properties displayed during molecular dynamicssimulations in order to minimize manual intervention. This paves the way for applying the aiGK method insemiautomated and high-throughput frameworks. The proposed strategies are presented and demonstrated forcomputing the lattice thermal conductivity at room temperature in the mildly anharmonic periclase MgO, andfor the strongly anharmonic marshite CuI.

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  • 12.
    Knoop, Florian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft; Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Purcell, Thomas A. R.
    The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft; Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Scheffler, Matthias
    The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft; Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Carbogno, Christian
    The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft; Germany; IRIS-Adlershof of the Humboldt-Universität zu Berlin, Germany.
    Anharmonicity in Thermal Insulators: An Analysis from First Principles2023In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 130, no 23, article id 236301Article in journal (Refereed)
    Abstract [en]

    The anharmonicity of atomic motion limits the thermal conductivity in crystalline solids. However, amicroscopic understanding of the mechanisms active in strong thermal insulators is lacking. In this Letter,we classify 465 experimentally known materials with respect to their anharmonicity and perform fullyanharmonic ab initio Green-Kubo calculations for 58 of them, finding 28 thermal insulators withκ < 10 W=mK including 6 with ultralow κ ≲ 1 W=mK. Our analysis reveals that the underlying stronganharmonic dynamics is driven by the exploration of metastable intrinsic defect geometries. This is atvariance with the frequently applied perturbative approach, in which the dynamics is assumed to evolvearound a single stable geometry.

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  • 13.
    Laniel, Dominique
    et al.
    Univ Bayreuth, Germany; Univ Edinburgh, Scotland.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Yin, Yuqing
    Univ Bayreuth, Germany; Shandong Univ, Peoples R China.
    Fedotenko, Timofey
    Univ Bayreuth, Germany.
    Khandarkhaeva, Saiana
    Univ Bayreuth, Germany.
    Aslandukov, Andrey
    Univ Bayreuth, Germany.
    Aprilis, Georgios
    European Synchrotron Radiat Facil, France.
    Abrikosov, Alexei I.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Masood, Talha Bin
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Giacobbe, Carlotta
    European Synchrotron Radiat Facil, France.
    Bright, Eleanor Lawrence
    European Synchrotron Radiat Facil, France.
    Glazyrin, Konstantin
    Photon Sci, Germany.
    Hanfland, Michael
    European Synchrotron Radiat Facil, France.
    Wright, Jonathan
    European Synchrotron Radiat Facil, France.
    Hotz, Ingrid
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Dubrovinsky, Leonid
    Shandong Univ, Peoples R China.
    Doubrovinckaia, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Aromatic hexazine [N6]4− anion featured in the complex structure of the high-pressure potassium nitrogen compound K9N562023In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 15, no 5, p. 641-646Article in journal (Refereed)
    Abstract [en]

    The recent high-pressure synthesis of pentazolates and the subsequent stabilization of the aromatic [N-5](-) anion at atmospheric pressure have had an immense impact on nitrogen chemistry. Other aromatic nitrogen species have also been actively sought, including the hexaazabenzene N-6 ring. Although a variety of configurations and geometries have been proposed based on ab initio calculations, one that stands out as a likely candidate is the aromatic hexazine anion [N-6](4-). Here we present the synthesis of this species, realized in the high-pressure potassium nitrogen compound K9N56 formed at high pressures (46 and 61 GPa) and high temperature (estimated to be above 2,000 K) by direct reaction between nitrogen and KN3 in a laser-heated diamond anvil cell. The complex structure of K9N56-composed of 520 atoms per unit cell-was solved based on synchrotron single-crystal X-ray diffraction and corroborated by density functional theory calculations. The observed hexazine anion [N-6](4-) is planar and proposed to be aromatic.

  • 14.
    Fiantok, Tomas
    et al.
    Comenius Univ, Slovakia; Comenius Univ, Slovakia.
    Koutna, Nikola
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. TU Wien, Austria.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Mikula, Marian
    Comenius Univ, Slovakia; SAS, Slovakia.
    Ceramic transition metal diboride superlattices with improved ductility and fracture toughness screened by ab initio calculations2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 12835Article in journal (Refereed)
    Abstract [en]

    Inherent brittleness, which easily leads to crack formation and propagation during use, is a serious problem for protective ceramic thin-film applications. Superlattice architectures, with alternating nm-thick layers of typically softer/stiffer materials, have been proven powerful method to improve the mechanical performance of, e.g., cubic transition metal nitride ceramics. Using high-throughput first-principles calculations, we propose that superlattice structures hold promise also for enhancing mechanical properties and fracture resistance of transition metal diborides with two competing hexagonal phases, a and ?. We study 264 possible combinations of a/a, a/? or co/co MB2 (where M = Al or group 3-6 transition metal) diboride superlattices. Based on energetic stability considerations, together with restrictions for lattice and shear modulus mismatch (?a &lt; 4%, ?G &gt; 40 GPa), we select 33 superlattice systems for further investigations. The identified systems are analysed in terms of mechanical stability and elastic constants, C-ij, where the latter provide indication of in-plane vs. out of-plane strength ( C-11, C-33 ) and ductility ( C-13 - C-44, C-12 - C-66 ). The superlattice ability to resist brittle cleavage along interfaces is estimated by Griffiths formula for fracture toughness. The a/a-type TiB2 /MB2 (M = Mo, W), HfB2/WB2, VB2/MB2 (M = Cr, Mo), NbB2/MB2 (M = Mo, W), and a/?-type AlB2/MB2 (M = Nb, Ta, Mo, W), are suggested as the most promising candidates providing atomic-scale basis for enhanced toughness and resistance to crack growth.

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  • 15.
    Sangiovanni, Davide
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Faccio, Ricardo
    Univ Republica, Uruguay.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kakanakova-Gueorguieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Correction: Discovering atomistic pathways for supply of metal atoms from methyl-based precursors to graphene surface (vol 25, pg 829, 2023)2023In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, no 7, p. 5887-5887Article in journal (Other academic)
    Abstract [en]

    Correction for Discovering atomistic pathways for supply of metal atoms from methyl-based precursors to graphene surface by Davide G. Sangiovanni et al., Phys. Chem. Chem. Phys., 2023, 25, 829-837, https://doi.org/10.1039/D2CP04091C.

  • 16.
    Sangiovanni, Davide
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Kraych, Antoine
    Ruhr Univ Bochum, Germany.
    Mrovec, Matous
    Ruhr Univ Bochum, Germany.
    Salamania, Janella
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Descriptor for slip-induced crack blunting in refractory ceramics2023In: Physical Review Materials, E-ISSN 2475-9953, Vol. 7, no 10, article id 103601Article in journal (Refereed)
    Abstract [en]

    Understanding the competition between brittleness and plasticity in refractory ceramics is of importance for aiding design of hard materials with enhanced fracture resistance. Inspired by experimental observations of crack shielding due to dislocation activity in TiN ceramics [Kumar et al., Int. J. Plast. 27, 739 (2011)], we carry out comprehensive atomistic investigations to identify mechanisms responsible for brittleness and slip-induced plasticity in Ti-N systems. First, we validate a semiempirical interatomic potential against density-functional theory results of Griffith and Rice stress intensities for cleavage (K-Ic) and dislocation emission (K-Ie) as well as ab initio molecular dynamics mechanical-testing simulations of pristine and defective TiN lattices at temperatures between 300 and 1200 K. The calculated K-Ic and K-Ie values indicate intrinsic brittleness, as K-Ic &lt;&lt; K-Ie. However, KI-controlled molecular statics simulations-which reliably forecast macroscale mechanical properties through nanoscale modeling-reveal that slip plasticity can be promoted by a reduced sharpness of the crack and/or the presence of anion vacancies. Classical molecular dynamics simulations of notched Ti-N supercell models subject to tension provide a qualitative understanding of the competition between brittleness and plasticity at finite temperatures. Although crack growth occurs in most cases, a sufficiently rapid accumulation of shear stress at the notch tip may postpone or prevent fracture via nucleation and emission of dislocations. Furthermore, we show that the probability to observe slip-induced plasticity leading to crack blunting in flawed Ti-N lattices correlates with the ideal tensile/shear strength ratio (I-plasticity(slip)) of pristine Ti-N crystals. We propose that the I-plasticity(slip) descriptor should be considered for ranking the ability of ceramics to blunt cracks via dislocation-mediated plasticity at finite temperatures.

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  • 17.
    Meier, Thomas
    et al.
    Center for High Pressure Science and Technology Advance Research, Beijing, China.
    Laniel, Dominique
    Center for Science at Extreme Conditions, University of Edinburgh, Edinburgh, United Kingdom.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Direct hydrogen quantification in high-pressure metal hydrides2023In: Matter and Radiation at Extremes, ISSN 2468-2047, Vol. 8, no 1, article id 018401Article in journal (Refereed)
    Abstract [en]

    High-pressure metal hydride (MH) research evolved into a thriving field within condensed matter physics following the realization of metallic compounds showing phonon mediated near room-temperature superconductivity. However, severe limitations in determining the chemical formula of the reaction products, especially with regards to their hydrogen content, impedes a deep understanding of the synthesized phases and can lead to significantly erroneous conclusions. Here, we present a way to directly access the hydrogen content of MH solids synthesized at high pressures in (laser-heated) diamond anvil cells using nuclear magnetic resonance spectroscopy. We show that this method can be used to investigate MH compounds with a wide range of hydrogen content, from MHx with x = 0.15 (CuH0.15) to x ≲ 6.4 (H6±0.4S5).

  • 18.
    Pshyk, Oleksandr V.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Li, Xiao
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory, University of Illinois, Urbana, IL, United States.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Discovery of Guinier-Preston zone hardening in refractory nitride ceramics2023In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 255, article id 119105Article in journal (Refereed)
    Abstract [en]

    Traditional age hardening mechanisms in refractory ceramics consist of precipitation of fine particles. These processes are vital for widespread wear-resistant coating applications. Here, we report novel Guinier-Preston zone hardening, previously only known to operate in soft light-metal alloys, taking place in refractory ceramics like multicomponent nitrides. The added superhardening, discovered in thin films of Ti-Al-W-N upon high temperature annealing, comes from the formation of atomic-plane-thick W disks populating {111} planes of the cubic matrix, as observed by atomically resolved high resolution scanning transmission electron microscopy and corroborated by ab initio calculations and molecular dynamics simulations. Guinier-Preston zone hardening concurrent with spinodal decomposition is projected to exist in a range of other ceramic solid solutions and thus provides a new approach for the development of advanced materials with outstanding mechanical properties and higher operational temperature range for the future demanding applications.

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  • 19.
    Baldwin, William J.
    et al.
    Univ Cambridge, England.
    Liang, Xia
    Imperial Coll London, England.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial Coll London, England.
    Dubajic, Milos
    Univ Cambridge, England.
    Dell Angelo, David
    Unita Cagliari, Italy.
    Sutton, Christopher
    Univ South Carolina, SC 29208 USA.
    Caddeo, Claudia
    Unita Cagliari, Italy.
    Stranks, Samuel D.
    Univ Cambridge, England.
    Mattoni, Alessandro
    Unita Cagliari, Italy.
    Walsh, Aron
    Imperial Coll London, England.
    Csanyi, Gabor
    Univ Cambridge, England.
    Dynamic Local Structure in Caesium Lead Iodide: Spatial Correlation and Transient Domains2023In: Small, ISSN 1613-6810, E-ISSN 1613-6829Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites are multifunctional semiconductors with tunable structures and properties. They are highly dynamic crystals with complex octahedral tilting patterns and strongly anharmonic atomic behavior. In the higher temperature, higher symmetry phases of these materials, several complex structural features are observed. The local structure can differ greatly from the average structure and there is evidence that dynamic 2D structures of correlated octahedral motion form. An understanding of the underlying complex atomistic dynamics is, however, still lacking. In this work, the local structure of the inorganic perovskite CsPbI3 is investigated using a new machine learning force field based on the atomic cluster expansion framework. Through analysis of the temporal and spatial correlation observed during large-scale simulations, it is revealed that the low frequency motion of octahedral tilts implies a double-well effective potential landscape, even well into the cubic phase. Moreover, dynamic local regions of lower symmetry are present within both higher symmetry phases. These regions are planar and the length and timescales of the motion are reported. Finally, the spatial arrangement of these features and their interactions are investigated and visualized, providing a comprehensive picture of local structure in the higher symmetry phases.

  • 20.
    Klarbring, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Singh, Utkarsh
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Electronic structure of the magnetic halide double perovskites Cs-2(Ag, Na)FeCl6 from first principles2023In: Physical Review Materials, E-ISSN 2475-9953, Vol. 7, no 4, article id 044605Article in journal (Refereed)
    Abstract [en]

    A family of magnetic halide double perovskites (HDPs) have recently attracted attention due to their potential to broaden application areas of halide double perovskites into, e.g., spintronics. Up to date the theoretical modeling of these systems have relied on primitive approximations to the density functional theory (DFT). In this paper, we study structural, electronic and magnetic properties of the Fe3+-containing HDPs Cs2AgFeCl6 and Cs2NaFeCl6 using a combination of more advanced DFT-based methods, including DFT + U, hybrid-DFT, and treatments of various magnetic states. We examine the effect of varying the effective Hubbard parameter, U-eff, in DFT + U and the mixing-parameter, alpha, in hybrid DFT on the electronic structure and structural properties. Our results reveal a set of localized Fe(d) states that are highly sensitive to these parameters. Cs2AgFeCl6 and Cs2NaFeCl6 are both antiferromagnets with Neel temperatures well below room temperature and are thus in their paramagnetic (PM) state at the external conditions relevant to most applications. Therefore, we have examined the effect of disordered magnetism on the electronic structure of these systems and find that while Cs2NaFeCl6 is largely unaffected, Cs2AgFeCl6 shows significant renormalization of its electronic band structure.

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  • 21.
    Ramanath, Ganpati
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rensselaer Polytech Inst, NY 12180 USA.
    Rowe, Collin
    Rensselaer Polytech Inst, NY 12180 USA.
    Sharma, Geetu
    Rensselaer Polytech Inst, NY 12180 USA.
    Venkataramani, Venkat
    Rensselaer Polytech Inst, NY 12180 USA.
    Alauzun, Johan G.
    Univ Montpellier, France.
    Sundararaman, Ravishankar
    Rensselaer Polytech Inst, NY 12180 USA.
    Keblinski, Pawel
    Rensselaer Polytech Inst, NY 12180 USA.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Engineering inorganic interfaces using molecular nanolayers2023In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 122, no 26, article id 260502Article in journal (Refereed)
    Abstract [en]

    Advances in interface science over the last 20 years have demonstrated the use of molecular nanolayers (MNLs) at inorganic interfaces to access emergent phenomena and enhance a variety of interfacial properties. Here, we capture important aspects of how a MNL can induce multifold enhancements and tune multiple interfacial properties, including chemical stability, fracture energy, thermal and electrical transport, and electronic structure. Key challenges that need to be addressed for the maturation of this emerging field are described and discussed. MNL-induced interfacial engineering has opened up attractive opportunities for designing organic-inorganic hybrid nanomaterials with high interface fractions, where properties are determined predominantly by MNL-induced interfacial effects for applications.

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  • 22.
    Singh, Utkarsh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Exploring magnetism of lead-free halide double perovskites: A high-throughput first-principles study2023In: Physical Review Materials, E-ISSN 2475-9953, Vol. 7, no 11, article id 114404Article in journal (Refereed)
    Abstract [en]

    We have performed a comprehensive, first-principles high-throughput study of the magnetic properties of halide double perovskites, Cs2BBCl-6, with magnetic ions occupying one or both B and B sites. Our findings indicate a general tendency for these materials to exhibit antiferromagnetic ordering with low Neel temperatures. At the same time, we reveal a few potential candidates that predicted to be ferromagnetic with relatively high Curie temperatures. Achieving ferromagnetic coupling might be feasible via simultaneously alloying at B and B sites with magnetic 3d and nonmagnetic 5d ions. With this approach, we discover that Cs2HgCrCl6, Cs2AgNiCl6, and Cs2AuNiCl6 have high Curie temperatures relative to their peers, with the latter two exhibiting half metallic behavior. Further, this study illuminates the underpinning mechanism of magnetic exchange interactions in halide double perovskites, enabling a deeper understanding of their magnetic behavior. Our findings, especially the discovery of the compounds with robust half metallic properties and high Curie temperatures, hold promise for potential applications in the field of spintronics.

  • 23.
    Vekilova, Olga Yu.
    et al.
    Stockholm Univ, Sweden; AlbaNova Univ Ctr, Sweden.
    Beyer, Doreen. C. C.
    Univ Leipzig, Germany.
    Bhat, Shrikant
    Deutsch Elektronen Synchrotron DESY, Germany.
    Farla, Robert
    Deutsch Elektronen Synchrotron DESY, Germany.
    Baran, Volodymyr
    Deutsch Elektronen Synchrotron DESY, Germany.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Kohlmann, Holger
    Univ Leipzig, Germany.
    Haussermann, Ulrich
    Stockholm Univ, Sweden.
    Spektor, Kristina
    Univ Leipzig, Germany; Deutsch Elektronen Synchrotron DESY, Germany.
    Formation and Polymorphism of Semiconducting K2SiH6 and Strategy for Metallization2023In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 62, no 21, p. 8093-8100Article in journal (Refereed)
    Abstract [en]

    K2SiH6, crystallizing in the cubicK(2)PtCl(6) structure type (Fm3 &#x305;m), features unusual hypervalent SiH6 (2-) complexes. Here, the formation of K2SiH6 athigh pressures is revisited by in situ synchrotron diffraction experiments,considering KSiH3 as a precursor. At the investigated pressures,8 and 13 GPa, K2SiH6 adopts the trigonal (NH4)(2)SiF6 structure type (P3 &#x305;m1) upon formation. The trigonal polymorphis stable up to 725 & DEG;C at 13 GPa. At room temperature, the transitioninto an ambient pressure recoverable cubic form occurs below 6.7 GPa.Theory suggests the existence of an additional, hexagonal, variantin the pressure interval 3-5 GPa. According to density functionaltheory band structure calculations, K2SiH6 isa semiconductor with a band gap around 2 eV. Nonbonding H-dominatedstates are situated below and Si-H anti-bonding states arelocated above the Fermi level. Enthalpically feasible and dynamicallystable metallic variants of K2SiH6 may be obtainedwhen substituting Si partially by Al or P, thus inducing p- and n-typemetallicity, respectively. Yet, electron-phonon coupling appearsweak, and calculated superconducting transition temperatures are &lt;1K. The formation of K2SiH6 at high pressuresstarting from KSiH3 or mixtures of KH and KSiH3 is investigated by in situ synchrotron diffraction experiments.Between 6.5 and 13 GPa, K2SiH6 adopts the trigonal(NH4)(2)SiF6 structure type (P3 &#x305;m1), which is stable up to 725 & DEG;C at 13 GPa. At room temperature, the transition into an ambientpressure-recoverable cubic form occurs below 6.5 GPa.

  • 24.
    Levämäki, Henrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Bock, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Johnson, Lars J. S.
    Sandvik Coromant, Sweden.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Armiento, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    HADB: A materials-property database for hard-coating alloys2023In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 766, article id 139627Article in journal (Refereed)
    Abstract [en]

    Data-driven approaches are becoming increasingly valuable for modern science, and they are making their way into industrial research and development (R&D). Supervised machine learning of statistical models can utilize databases of materials parameters to speed up the exploration of candidate materials for experimental synthesis and characterization. In this paper we introduce the HADB database, which contains properties of industrially relevant chemically disordered hard-coating alloys, focusing on their thermodynamic, elastic and mechanical properties. We present the technical implementations of the database infrastructure including support for browse, query, retrieval, and API access through the OPTIMADE API to make this data findable, accessible, interoperable, and reusable (FAIR). Finally, we demonstrate the usefulness of the database by training a graph -based machine learning (ML) model to predict elastic properties of hard-coating alloys. The ML model is shown to predict bulk and shear moduli for out out-of-sample alloys with less than 6 GPa mean average error.

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  • 25.
    Akbar, Fariia Iasmin
    et al.
    Univ Bayreuth, Germany; Univ Bayreuth, Germany.
    Aslandukova, Alena
    Univ Bayreuth, Germany.
    Aslandukov, Andrey
    Univ Bayreuth, Germany; Univ Bayreuth, Germany.
    Yin, Yuqing
    Univ Bayreuth, Germany; Shandong Univ, Peoples R China.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Khandarkhaeva, Saiana
    Univ Bayreuth, Germany.
    Fedotenko, Timofey
    Deutsch Elektronen Synchrotron DESY, Germany.
    Laniel, Dominique
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Bykov, Maxim
    Univ Cologne, Germany.
    Bykova, Elena
    Univ Bayreuth, Germany.
    Doubrovinckaia, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Univ Bayreuth, Germany.
    Dubrovinsky, Leonid
    Univ Bayreuth, Germany.
    High-pressure synthesis of dysprosium carbides2023In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 11, article id 1210081Article in journal (Refereed)
    Abstract [en]

    Chemical reactions between dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures of 19, 55, and 58 GPa and temperatures of similar to 2500 K. In situ single-crystal synchrotron X-ray diffraction analysis of the reaction products revealed the formation of novel dysprosium carbides, Dy4C3 and Dy3C2, and dysprosium sesquicarbide Dy2C3 previously known only at ambient conditions. The structure of Dy4C3 was found to be closely related to that of dysprosium sesquicarbide Dy2C3 with the Pu2C3-type structure. Ab initio calculations reproduce well crystal structures of all synthesized phases and predict their compressional behavior in agreement with our experimental data. Our work gives evidence that high-pressure synthesis conditions enrich the chemistry of rare earth metal carbides.

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  • 26.
    Salamania, Janella
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Calamba Kwick, Katherine
    Sandvik Coromant AB, Stockholm, Sweden.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Rogström, Lina
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Johnson, Lars
    Sandvik Coromant AB, Stockholm, Sweden.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    High-resolution STEM investigation of the role of dislocations during decomposition of Ti1-xAlxNy2023In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 229, article id 115366Article in journal (Refereed)
    Abstract [en]

    The defect structures forming during high-temperature decomposition of Ti1-xAlxNy films were investigated through high-resolution scanning transmission electron microscopy. After annealing to 950 °C, misfit edge dislocations a/6〈112〉{111} partial dislocations permeate the interface between TiN-rich and AlN-rich domains to accommodate lattice misfits during spinodal decomposition. The stacking fault energy associated with the partial dislocations decreases with increasing Al content, which facilitates the coherent cubic to wurtzite structure transition of AlN-rich domains. The wurtzite AlN-rich structure is recovered when every third cubic {111} plane is shifted by along the [211] direction. After annealing to 1100 °C, a temperature where coarsening dominates the microstructure evolution, we observe intersections of stacking faults, which form sessile locks at the interface of the TiN- and AlN-rich domains. These observed defect structures facilitate the formation of semicoherent interfaces and contribute to hardening in Ti1-xAlxNy.

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  • 27.
    Spektor, Kristina
    et al.
    Univ Leipzig, Germany; Deutsch Elektronen Synchrotron DESY, Germany.
    Kohlmann, Holger
    Univ Leipzig, Germany.
    Druzhbin, Dmitrii
    ESRF European Synchrotron Radiat Facil, France.
    Crichton, Wilson A.
    ESRF European Synchrotron Radiat Facil, France.
    Bhat, Shrikant
    Deutsch Elektronen Synchrotron DESY, Germany.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Vekilova, Olga Yu
    Stockholm Univ, Sweden.
    Haeussermann, Ulrich
    Stockholm Univ, Sweden.
    Hypervalent hydridosilicate in the Na-Si-H system2023In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 11, article id 1251774Article in journal (Refereed)
    Abstract [en]

    Hydrogenation reactions at gigapascal pressures can yield hydrogen-rich materials with properties relating to superconductivity, ion conductivity, and hydrogen storage. Here, we investigated the ternary Na-Si-H system by computational structure prediction and in situ synchrotron diffraction studies of reaction mixtures NaH-Si-H-2 at 5-10 GPa. Structure prediction indicated the existence of various hypervalent hydridosilicate phases with compositions NamSiH(4+m) (m = 1-3) at comparatively low pressures, 0-20 GPa. These ternary Na-Si-H phases share, as a common structural feature, octahedral SiH62- complexes which are condensed into chains for m = 1 and occur as isolated species for m = 2, 3. In situ studies demonstrated the formation of the double salt Na-3[SiH6]H (Na3SiH7, m = 3) containing both octahedral SiH62- moieties and hydridic H-. Upon formation at elevated temperatures (&gt;500 degrees C), Na3SiH7 attains a tetragonal structure (P4/mbm, Z = 2) which, during cooling, transforms to an orthorhombic polymorph (Pbam, Z = 4). Upon decompression, Pbam-Na3SiH7 was retained to approx. 4.5 GPa, below which a further transition into a yet unknown polymorph occurred. Na3SiH7 is a new representative of yet elusive hydridosilicate compounds. Its double salt nature and polymorphism are strongly reminiscent of fluorosilicates and germanates.

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  • 28.
    Mosquera-Lois, Irea
    et al.
    Imperial Coll London, England.
    Kavanagh, Sean R.
    Imperial Coll London, England; UCL, England.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial Coll London, England.
    Tolborg, Kasper
    Imperial Coll London, England.
    Walsh, Aron
    Imperial Coll London, England; Ewha Womans Univ, South Korea.
    Imperfections are not 0 K: free energy of point defects in crystals2023In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 52, no 17, p. 5812-5826Article, review/survey (Refereed)
    Abstract [en]

    Defects determine many important properties and applications of materials, ranging from doping in semiconductors, to conductivity in mixed ionic-electronic conductors used in batteries, to active sites in catalysts. The theoretical description of defect formation in crystals has evolved substantially over the past century. Advances in supercomputing hardware, and the integration of new computational techniques such as machine learning, provide an opportunity to model longer length and time-scales than previously possible. In this Tutorial Review, we cover the description of free energies for defect formation at finite temperatures, including configurational (structural, electronic, spin) and vibrational terms. We discuss challenges in accounting for metastable defect configurations, progress such as machine learning force fields and thermodynamic integration to directly access entropic contributions, and bottlenecks in going beyond the dilute limit of defect formation. Such developments are necessary to support a new era of accurate defect predictions in computational materials chemistry.

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  • 29.
    Chen, Zhuo
    et al.
    Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria.
    Huang, Yong
    Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria.
    Koutná, Nikola
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Institute of Materials Science and Technology, TU Wien, A-1060, Vienna, Austria.
    Gao, Zecui
    Institute of Materials Science and Technology, TU Wien, Vienna, Austria.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Fellner, Simon
    Institute of Materials Science and Technology, TU Wien, Vienna, Austria.
    Haberfehlner, Georg
    Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Graz, Austria.
    Jin, Shengli
    Chair of Ceramics, Montanuniversität Leoben, Leoben, Austria.
    Mayrhofer, Paul H.
    Institute of Materials Science and Technology, TU Wien, Vienna, Austria.
    Kothleitner, Gerald
    Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Graz, Austria; Graz Centre for Electron Microscopy, Graz, Austria.
    Zhang, Zaoli
    Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria; Department of Materials Science, Montanuniversität Leoben, Leoben, Austria.
    Large mechanical properties enhancement in ceramics through vacancy-mediated unit cell disturbance2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 8387Article in journal (Refereed)
    Abstract [en]

    Tailoring vacancies is a feasible way to improve the mechanical properties of ceramics. However, high concentrations of vacancies usually compromise the strength (or hardness). We show that a high elasticity and flexural strength could be achieved simultaneously using a nitride superlattice architecture with disordered anion vacancies up to 50%. Enhanced mechanical properties primarily result from a distinctive deformation mechanism in superlattice ceramics, i.e., unit-cell disturbances. Such a disturbance substantially relieves local high-stress concentration, thus enhancing deformability. No dislocation activity involved also rationalizes its high strength. The work renders a unique understanding of the deformation and strengthening/toughening mechanism in nitride ceramics.

  • 30.
    Zhang, Bin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ji, Fuxiang
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Rudko, Galyna
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Lattice Dynamics and Electron-Phonon Coupling in Double Perovskite Cs2NaFeCl62023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 4, p. 1908-1916Article in journal (Refereed)
    Abstract [en]

    Phonon-phonon and electron/exciton-phonon coupling play a vitally important role in thermal, electronic, as well as optical properties of metal halide perovskites. In this work, we evaluate phonon anharmonicity and coupling between electronic and vibrational excitations in novel double perovskite Cs2NaFeCl6 single crystals. By employing comprehensive Raman measurements combined with first-principles theoretical calculations, we identify four Raman-active vibrational modes. Polarization properties of these modes imply Fm (3) over barm symmetry of the lattice, indicative for on average an ordered distribution of Fe and Na atoms in the lattice. We further show that temperature dependence of the Raman modes, such as changes in the phonon line width and their energies, suggests high phonon anharmonicity, typical for double perovskite materials. Resonant multiphonon Raman scattering reveals the presence of high-lying band states that mediate strong electron-phonon coupling and give rise to intense nA(1g) overtones up to the fifth order. Strong electron-phonon coupling in Cs2NaFeCl6 is also concluded based on the Urbach tail analysis of the absorption coefficient and the calculated Frohlich coupling constant. Our results, therefore, suggest significant impacts of phonon-phonon and electron-phonon interactions on electronic properties of Cs2NaFeCl6, important for potential applications of this novel material.

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  • 31.
    Ekström, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hurand, Simon
    Univ Poitiers, France.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sharma, Geetu
    Rensselaer Polytech Inst, NY 12180 USA.
    Voznyy, Oleksandr
    Univ Toronto Scarborough, Canada.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ramanath, Ganpati
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rensselaer Polytech Inst, NY 12180 USA.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Microstructure control and property switching in stress-free van der Waals epitaxial VO2 films on mica2023In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 229, article id 111864Article in journal (Refereed)
    Abstract [en]

    Realizing stress-free inorganic epitaxial films on weakly bonding substrates is of importance for applications that require film transfer onto surfaces that do not seed epitaxy. Film-substrate bonding is usually weakened by harnessing natural van der Waals layers (e.g., graphene) on substrate surfaces, but this is difficult to achieve in non-layered materials. Here, we demonstrate van der Waals epitaxy of stress-free films of a non-layered material VO2 on mica. The films exhibit out-of-plane 010 texture with three inplane orientations inherited from the crystallographic domains of the substrate. The lattice parameters are invariant with film thickness, indicating weak film-substrate bonding and complete interfacial stress relaxation. The out-of-plane domain size scales monotonically with film thickness, but the in-plane domain size exhibits a minimum, indicating that the nucleation of large in-plane domains supports subsequent island growth. Complementary ab initio investigations suggest that VO2 nucleation and van der Waals epitaxy involves subtle polarization effects around, and the active participation of, surface potassium atoms on the mica surface. The VO2 films show a narrow domain-size-sensitive electrical-conductiv ity-temperature hysteresis. These results offer promise for tuning the properties of stress-free van der Waals epitaxial films of non-layered materials such as VO2 through microstructure control (C) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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  • 32.
    Krenzer, Gabriel
    et al.
    Imperial Coll London, England.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial Coll London, England.
    Tolborg, Kasper
    Imperial Coll London, England; Imperial Coll London, England.
    Rossignol, Hugo
    Trinity Coll Dublin, Ireland; Trinity Coll Dublin, Ireland.
    McCluskey, Andrew R.
    European Spallat Source ER, Denmark.
    Morgan, Benjamin J.
    Univ Bath, England.
    Walsh, Aron
    Imperial Coll London, England; Ewha Womans Univ, South Korea.
    Nature of the Superionic Phase Transition of Lithium Nitride from Machine Learning Force Fields2023In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 35, no 15, p. 6133-6140Article in journal (Refereed)
    Abstract [en]

    Superionic conductors have great potential as solid-stateelectrolytes,but the physics of type-II superionic transitions remains elusive.In this study, we employed molecular dynamics simulations, using machinelearning force fields, to investigate the type-II superionic phasetransition in & alpha;-Li3N. We characterized Li3N above and below the superionic phase transition by calculatingthe heat capacity, Li+ ion self-diffusion coefficient,and Li defect concentrations as functions of temperature. Our findingsindicate that both the Li+ self-diffusion coefficient andLi vacancy concentration follow distinct Arrhenius relationships inthe normal and superionic regimes. The activation energies for self-diffusionand Li vacancy formation decrease by a similar proportion across thesuperionic phase transition. This result suggests that the superionictransition may be driven by a decrease in defect formation energeticsrather than changes in Li transport mechanism. This insight may haveimplications for other type-II superionic materials.

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  • 33.
    Gambino, Davide
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial Coll London, England.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Phase stability of Fe from first principles: Atomistic spin dynamics coupled with ab initio molecular dynamics simulations and thermodynamic integration2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 1, article id 014102Article in journal (Refereed)
    Abstract [en]

    The calculation of free energies from first principles enables the prediction of phase stability of materials with high accuracy; these calculations are complicated in magnetic materials by the interplay of electronic, magnetic, and vibrational degrees of freedom. In this work, we show the feasibility and accuracy of the calculation of phase stability in magnetic systems with ab initio methods and thermodynamic integration by sampling the magnetic and vibrational phase space with coupled atomistic spin dynamics-ab initio molecular dynamics simulations [Stockem et al., PRL 121, 125902 (2018)], where energies and interatomic forces are calculated with density functional theory. We employ the method to calculate the phase stability of Fe at ambient pressure from 800 up to 1800 K. The Gibbs free energy difference between fcc and bcc Fe at zero pressure is calculated with thermodynamic integration over temperature and over stress-strain variables and, for the best set of exchange interactions employed, the Gibbs free energy difference between the two structures is within 5 meV/atom from the CALPHAD estimate, corresponding to an error in transition temperature below 150 K. The present work paves the way to free energy calculations in magnetic materials from first principles with accuracy in the order of 1 meV/atom.

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  • 34.
    Benshalom, Nimrod
    et al.
    Weizmann Inst Sci, Israel.
    Asher, Maor
    Weizmann Inst Sci, Israel.
    Jouclas, Remy
    Univ Libre Bruxelles ULB, Belgium.
    Korobko, Roman
    Weizmann Inst Sci, Israel.
    Schweicher, Guillaume
    Univ Libre Bruxelles ULB, Belgium.
    Liu, Jie
    Univ Libre Bruxelles ULB, Belgium.
    Geerts, Yves
    Univ Libre Bruxelles ULB, Belgium; Int Solvay Inst Phys & Chem, Belgium.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Weizmann Inst Sci, Israel.
    Yaffe, Omer
    Weizmann Inst Sci, Israel.
    Phonon-Phonon Interactions in the Polarization Dependence of Raman Scattering2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 36, p. 18099-18106Article in journal (Refereed)
    Abstract [en]

    We have found that the polarization dependence of Raman scattering in organic crystals at finite temperatures can only be described by a fourth-rank tensor formalism. This generalization of the second-rank Raman tensor stems from the effect of off diagonal components in the crystal self-energy on the light scattering mechanism. We thus establish a novel manifestation of phonon-phonon interaction in inelastic light scattering, markedly separate from the better-known phonon lifetime.

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  • 35.
    Ji, Fuxiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Zhang, Bin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Linqin
    School of Science Westlake University Hangzhou, P.R. China.
    Miao, Xiaohe
    Westlake University Hangzhou, P.R. China.
    Ning, Weihua
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Soochow University Suzhou, P. R. China.
    Zhang, Muyi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Cai, Xinyi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ren, Xiaoming
    State Key Laboratory of Materials‐Oriented Chemical Engineering and College of Chemistry and Molecular Engineering Nanjing Tech University Nanjing, P.R. China.
    Sun, Licheng
    Center of Artificial Photosynthesis for Solar Fuels, School of Science Westlake University Hangzhou,P.R. China.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials.
    Chen, Weimin
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials.
    Simak, Sergei I
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala University Uppsala SE‐75120 Sweden.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl62023In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, article id 2301102Article in journal (Refereed)
    Abstract [en]

    Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.

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  • 36.
    Langer, Marcel F.
    et al.
    Machine Learning Group, Technische Universität Berlin, Berlin, Germany; BIFOLD–Berlin Institute for the Foundations of Learning and Data, Berlin, Germany; The NOMAD Laboratory at the Fritz Haber Institute of the Max Planck Society and Humboldt University, Berlin, Germany.
    Frank, J. Thorben
    Machine Learning Group, Technische Universität Berlin, Berlin, Germany; BIFOLD–Berlin Institute for the Foundations of Learning and Data, Berlin, Germany.
    Knoop, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Stress and heat flux via automatic differentiation2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 159, no 17, article id 174105Article in journal (Refereed)
    Abstract [en]

    Machine-learning potentials provide computationally efficient and accurate approximations of the Born–Oppenheimer potential energy surface. This potential determines many materials properties and simulation techniques usually require its gradients, in particular forces and stress for molecular dynamics, and heat flux for thermal transport properties. Recently developed potentials feature high body order and can include equivariant semi-local interactions through message-passing mechanisms. Due to their complex functional forms, they rely on automatic differentiation (AD), overcoming the need for manual implementations or finite-difference schemes to evaluate gradients. This study discusses how to use AD to efficiently obtain forces, stress, and heat flux for such potentials, and provides a model-independent implementation. The method is tested on the Lennard-Jones potential, and then applied to predict cohesive properties and thermal conductivity of tin selenide using an equivariant message-passing neural network potential.

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  • 37.
    Liang, Xia
    et al.
    Imperial Coll London, England.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial Coll London, England.
    Baldwin, William J.
    Univ Cambridge, England.
    Li, Zhenzhu
    Imperial Coll London, England.
    Csanyi, Gabor
    Univ Cambridge, England.
    Walsh, Aron
    Imperial Coll London, England; Ewha Womans Univ, South Korea.
    Structural Dynamics Descriptors for Metal Halide Perovskites2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 38, p. 19141-19151Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have shown extraordinary performance in solar energy conversion technologies. They have been classified as "soft semiconductors" due to their flexible corner-sharing octahedral networks and polymorphous nature. Understanding the local and average structures continues to be challenging for both modeling and experiments. Here, we report the quantitative analysis of structural dynamics in time and space from molecular dynamics simulations of perovskite crystals. The compact descriptors provided cover a wide variety of structural properties, including octahedral tilting and distortion, local lattice parameters, molecular orientations, as well as their spatial correlation. To validate our methods, we have trained a machine learning force field (MLFF) for methylammonium lead bromide (CH3NH3PbBr3) using an on-the-fly training approach with Gaussian process regression. The known stable phases are reproduced, and we find an additional symmetry-breaking effect in the cubic and tetragonal phases close to the phase-transition temperature. To test the implementation for large trajectories, we also apply it to 69,120 atom simulations for CsPbI3 based on an MLFF developed using the atomic cluster expansion formalism. The structural dynamics descriptors and Python toolkit are general to perovskites and readily transferable to more complex compositions.

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  • 38.
    Laniel, Dominique
    et al.
    Univ Edinburgh, Scotland.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Aslandukov, Andrey
    Univ Bayreuth, Germany.
    Spender, James
    Univ Edinburgh, Scotland.
    Ranieri, Umbertoluca
    Univ Edinburgh, Scotland.
    Fedotenko, Timofey
    Glazyrin, Konstantin
    DESY, Germany.
    Bright, Eleanor Lawrence
    European Synchrotron Radiat Facil, France.
    Chariton, Stella
    Univ Chicago, IL 60637 USA.
    Prakapenka, Vitali B.
    Univ Chicago, IL 60637 USA.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Dubrovinsky, Leonid
    Univ Bayreuth, Germany.
    Doubrovinckaia, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Structure determination of ζ-N2 from single-crystal X-ray diffraction and theoretical suggestion for the formation of amorphous nitrogen2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 6207Article in journal (Refereed)
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  • 39.
    Yin, Yuqing
    et al.
    Shandong Univ, Peoples R China; Univ Bayreuth, Germany.
    Aslandukova, Alena
    Univ Bayreuth, Germany.
    Jena, Nityasagar
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Winkler, Bjoern
    Frankfurt Univ, Germany.
    Khandarkhaeva, Saiana
    Univ Bayreuth, Germany.
    Fedotenko, Timofey
    Deutsch Elektronen Synchrotron DESY, Germany.
    Bykova, Elena
    Univ Bayreuth, Germany; Carnegie Inst Sci, DC 20015 USA.
    Laniel, Dominique
    Univ Edinburgh, Scotland; Univ Edinburgh, Scotland.
    Bykov, Maxim
    Univ Cologne, Germany.
    Aslandukov, Andrey
    Univ Bayreuth, Germany; Univ Bayreuth, Germany.
    Akbar, Fariia I.
    Univ Bayreuth, Germany; Univ Bayreuth, Germany.
    Glazyrin, Konstantin
    Deutsch Elektronen Synchrotron DESY, Germany.
    Garbarino, Gaston
    European Synchrotron Radiat Facil, France.
    Giacobbe, Carlotta
    European Synchrotron Radiat Facil, France.
    Bright, Eleanor L.
    European Synchrotron Radiat Facil, France.
    Jia, Zhitai
    Shandong Univ, Peoples R China.
    Dubrovinsky, Leonid
    Univ Bayreuth, Germany.
    Doubrovinckaia, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Univ Bayreuth, Germany.
    Unraveling the Bonding Complexity of Polyhalogen Anions: High-Pressure Synthesis of Unpredicted Sodium Chlorides Na2Cl3 and Na4Cl5 and Bromide Na4Br52023In: JACS Au, E-ISSN 2691-3704, Vol. 3, no 6, p. 1634-1641Article in journal (Refereed)
    Abstract [en]

    The field of polyhalogen chemistry, specifically polyhalogenanions(polyhalides), is rapidly evolving. Here, we present the synthesisof three sodium halides with unpredicted chemical compositions andstructures (tP10-Na2Cl3, hP18-Na4Cl5, and hP18-Na4Br5), a series of isostructural cubic cP8-AX(3) halides (NaCl3, KCl3, NaBr3, and KBr3), and a trigonal potassiumchloride (hP24-KCl3). The high-pressuresyntheses were realized at 41-80 GPa in diamond anvil cellslaser-heated at about 2000 K. Single-crystal synchrotron X-ray diffraction(XRD) provided the first accurate structural data for the symmetrictrichloride Cl-3 (-) anion in hP24-KCl3 and revealed the existence of two different typesof infinite linear polyhalogen chains, [Cl]( infinity ) ( n-) and [Br]( infinity ) ( n-), in the structures of cP8-AX(3) compounds and in hP18-Na4Cl5 and hP18-Na4Br5. In Na4Cl5 and Na4Br5, we found unusually short, likely pressure-stabilized, contactsbetween sodium cations. Ab initio calculations support the analysisof structures, bonding, and properties of the studied halogenides.

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  • 40.
    Sangiovanni, Davide
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Kaufmann, Kevin
    Univ Calif San Diego, CA 92093 USA.
    Vecchio, Kenneth
    Univ Calif San Diego, CA 92093 USA.
    Valence electron concentration as key parameter to control the fracture resistance of refractory high-entropy carbides2023In: Science Advances, E-ISSN 2375-2548, Vol. 9, no 37, article id eadi2960Article in journal (Refereed)
    Abstract [en]

    Although high-entropy carbides (HECs) have hardness often superior to that of parent compounds, their brittleness-a problem shared with most ceramics-has severely limited their reliability. Refractory HECs in particular are attracting considerable interest due to their unique combination of mechanical and physical properties, tunable over a vast compositional space. Here, combining statistics of crack formation in bulk specimens subject to mild, moderate, and severe nanoindentation loading with ab initio molecular dynamics simulations of alloys under tension, we show that the resistance to fracture of cubic-B1 HECs correlates with their valence electron concentration (VEC). Electronic structure analyses show that VEC greater than or similar to 9.4 electrons per formula unit enhances alloy fracture resistance due to a facile rehybridization of electronic metallic states, which activates transformation plasticity at the yield point. Our work demonstrates a reliable strategy for computationally guided and rule based (i.e., VEC) engineering of deformation mechanisms in high entropy, solid solution, and doped ceramics.

  • 41.
    Aslandukov, Andrey
    et al.
    University of Bayreuth: Universitat Bayreuth Laboratory of Crystallography, Bayreuth, GERMANY.
    Trybel, Florian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Aslandukova, Alena
    University of Bayreuth: Universitat Bayreuth Bayerisches Geoinstitut, GERMANY.
    Laniel, Dominique
    The University of Edinburgh Centre for Science at Extreme Conditions and School of Physics and Astronomy, UNITED KINGDOM.
    Fedotenko, Timofey
    DESY: Deutsches Elektronen-Synchrotron Photon Science, Deutsches Elektronen-Synchrotron, GERMANY.
    Khandarkhaeva, Saiana
    University of Bayreuth: Universitat Bayreuth Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, GERMANY.
    Aprilis, Georgios
    ESRF European Synchrotron Radiation Facility, FRANCE.
    Giacobbe, Carlotta
    ESRF European Synchrotron Radiation Facility, FRANCE.
    Lawrence Bright, Eleanor
    ESRF European Synchrotron Radiation Facility, FRANCE.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Dubrovinsky, Leonid
    University of Bayreuth: Universitat Bayreuth Bayerisches Geoinstitut, GERMANY.
    Dubrovinskaia, Natalia
    University of Bayreuth: Universitat Bayreuth Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, GERMANY.
    Anionic N18 Macrocycles and a Polynitrogen Double Helix in Novel Yttrium Polynitrides YN6 and Y2N11 at 100 GPa2022In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 61, no 34, article id e202207469Article in journal (Refereed)
    Abstract [en]

    Two novel yttrium nitrides, YN6 and Y2N11, were synthesized by direct reaction between yttrium and nitrogen at 100 GPa and 3000 K in a laser-heated diamond anvil cell. High-pressure synchrotron single-crystal X-ray diffraction revealed that the crystal structures of YN6 and Y2N11 feature a unique organization of nitrogen atoms-a previously unknown anionic N-18 macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN6 and Y2N11 compounds, show an anion-driven metallicity, explaining the unusual bond orders in the polynitrogen units. As the charge state of the polynitrogen double helix in Y2N11 is different from that previously found in Hf2N11 and because N-18 macrocycles have never been predicted or observed, their discovery significantly extends the chemistry of polynitrides.

  • 42.
    Koutna, Nikola
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. TU Wien, Austria.
    Löfler, Lukas
    Dept Mat Sci, Austria; Rhein Westfal TH Aachen, Germany.
    Holec, David
    Dept Mat Sci, Austria.
    Chen, Zhuo
    Erich Schmid Inst Mat Sci, Austria.
    Zhang, Zaoli
    Erich Schmid Inst Mat Sci, Austria.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mayrhofer, Paul H.
    TU Wien, Austria.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Atomistic mechanisms underlying plasticity and crack growth in ceramics: a case study of AlN/TiN superlattices2022In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 229, article id 117809Article in journal (Refereed)
    Abstract [en]

    Interfaces between components of a material govern its mechanical strength and fracture resistance. While a great number of interfaces is present in nanolayered materials, such as superlattices, their fundamental role during mechanical loading lacks understanding. Here we combine ab initio and classical molecular dynamics simulations, nanoindentation, and transmission electron microscopy to reveal atomistic mechanisms underlying plasticity and crack growth in B1 AlN(001)/TiN(001) superlattices under loading. The system is a model for modern refractory ceramics used as protective coatings. The simulations demonstrate an anisotropic response to uniaxial tensile deformation in principal crystallographic directions due to different strain-activated plastic deformation mechanisms. Superlattices strained orthogonal to (001) interfaces show modest plasticity and cleave parallel to AlN/TiN layers. Contrarily, B1-to-B3 or B1-to-B4(B-k) phase transformations in AlN facilitate a remarkable toughness enhancement upon in plane [110] and [100] tensile elongation, respectively. We verify the predictions experimentally and conclude that strain-induced crack growth-via loss of interface coherency, dislocation-pinning at interfaces, or layer interpenetration followed by formation of slip bands-can be hindered by controlling the thicknesses of the superlattice nanolayered components.

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  • 43.
    Dippo, Olivia F.
    et al.
    Univ Calif San Diego, CA 92093 USA.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Wenger, Emma
    Univ Calif San Diego, CA 92093 USA.
    Vecchio, Kenneth S.
    Univ Calif San Diego, CA 92093 USA; Univ Calif San Diego, CA 92093 USA.
    Color and pseudogap tunability in multicomponent carbonitrides2022In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 217, article id 110600Article in journal (Refereed)
    Abstract [en]

    The design and tailoring of material color for both aesthetic and functionality is an ongoing topic of materials science and engineering research. In this work, a method is developed to tune and predict color and pseudogap energy of any compositional variation of B1-rocksalt structured Group 4 and 5 transition metal carbonitride. Optical properties of bulk multicomponent transition metal carbonitrides were characterized using reflectivity spectra. Optical pseudogap energies were extrapolated using the Tauc method, and color appearance was quantified in the Commission Internationale de lEclairage (CIE) Lightness*Chroma*hue (L*C*h) color space. Variations of color parameters chroma and hue were analyzed in terms of pseudogap energies and electronic band structures. Compositional variations were utilized to predictably tune aspects of the electronic structure, including the specificity of electronic transitions and the energy at which they occur, to tailor the materials color appearance and facilitate the formation of new carbonitride colors.

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  • 44.
    Krasilnikov, O. M.
    et al.
    Natl Univ Sci & Technol, Russia.
    Vekilov, Yu Kh
    Natl Univ Sci & Technol, Russia; Natl Univ Sci & Technol, Russia.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Comment on "Nonlinear elasticity of prestressed single crystals at high pressure and various elastic moduli"2022In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 105, no 22, article id 226101Article in journal (Other academic)
    Abstract [en]

    We show that elastic moduli of higher (third and fourth) order of prestressed single crystals at high pressure, obtained from the Gibbs free energy, enter the relation between the Cauchy stress and Lagrange finite-strain tensor the same way they do for the second-order elastic moduli and, therefore, directly describe the nonlinear elasticity of prestressed crystals.

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  • 45.
    Benshalom, Nimrod
    et al.
    Weizmann Inst Sci, Israel.
    Reuveni, Guy
    Weizmann Inst Sci, Israel.
    Korobko, Roman
    Weizmann Inst Sci, Israel.
    Yaffe, Omer
    Weizmann Inst Sci, Israel.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Weizmann Inst Sci, Israel.
    Dielectric response of rock-salt crystals at finite temperatures from first principles2022In: Physical Review Materials, E-ISSN 2475-9953, Vol. 6, no 3, article id 033607Article in journal (Refereed)
    Abstract [en]

    We combine ab initio simulations and Raman scattering measurements to demonstrate explicit anharmonic effects in the temperature-dependent dielectric response of a NaCl single crystal. We measure the temperature evolution of its Raman spectrum and compare it to both a quasiharmonic and anharmonic model. Results demonstrate the necessity of including anharmonic lattice dynamics to explain the dielectric response of NaCl, as it is manifested in Raman scattering. Our model fully captures the linear dielectric response of a crystal at finite temperatures and may therefore be used to calculate the temperature dependence of other material properties governed by it.

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  • 46.
    Sangiovanni, Davide
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Faccio, Ricardo
    Univ Republica, Uruguay; Univ Republica, Uruguay.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kakanakova-Gueorguieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Discovering atomistic pathways for supply of metal atoms from methyl-based precursors to graphene surface2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, no 1, p. 829-837Article in journal (Refereed)
    Abstract [en]

    Conceptual 2D group III nitrides and oxides (e.g., 2D InN and 2D InO) in heterostructures with graphene have been realized by metal-organic chemical vapor deposition (MOCVD). MOCVD is expected to bring forth the same impact in the advancement of 2D semiconductor materials as in the fabrication of established semiconductor materials and device heterostructures. MOCVD employs metal-organic precursors such as trimethyl-indium, -gallium, and -aluminum, with (strong) metal-carbon bonds. Mechanisms that regulate MOCVD processes at the atomic scale are largely unknown. Here, we employ density-functional molecular dynamics - accounting for van der Waals interactions - to identify the reaction pathways responsible for dissociation of the trimethylindium (TMIn) precursor in the gas phase as well as on top-layer and zero-layer graphene. The simulations reveal how collisions with hydrogen molecules, intramolecular or surface-mediated proton transfer, and direct TMIn/graphene reactions assist TMIn transformations, which ultimately enables delivery of In monomers or InH and CH3In admolecules, on graphene. This work provides knowledge for understanding the nucleation and intercalation mechanisms at the atomic scale and for carrying out epitaxial growth of 2D materials and graphene heterostructures.

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  • 47.
    Cohen, Adi
    et al.
    Weizmann Inst Sci, Israel.
    Brenner, Thomas M.
    Weizmann Inst Sci, Israel.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Sharma, Rituraj
    Weizmann Inst Sci, Israel.
    Fabini, Douglas H.
    Max Planck Inst Solid State Res, Germany.
    Korobko, Roman
    Weizmann Inst Sci, Israel.
    Nayak, Pabitra K.
    Tata Inst Fundamental Res, India.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Yaffe, Omer
    Weizmann Inst Sci, Israel.
    Diverging Expressions of Anharmonicity in Halide Perovskites2022In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 34, no 14, article id 2107932Article in journal (Refereed)
    Abstract [en]

    Lead-based halide perovskite crystals are shown to have strongly anharmonic structural dynamics. This behavior is important because it may be the origin of their exceptional photovoltaic properties. The double perovskite, Cs2AgBiBr6, has been recently studied as a lead-free alternative for optoelectronic applications. However, it does not exhibit the excellent photovoltaic activity of the lead-based halide perovskites. Therefore, to explore the correlation between the anharmonic structural dynamics and optoelectronic properties in lead-based halide perovskites, the structural dynamics of Cs2AgBiBr6 are investigated and are compared to its lead-based analog, CsPbBr3. Using temperature-dependent Raman measurements, it is found that both materials are indeed strongly anharmonic. Nonetheless, the expression of their anharmonic behavior is markedly different. Cs2AgBiBr6 has well-defined normal modes throughout the measured temperature range, while CsPbBr3 exhibits a complete breakdown of the normal-mode picture above 200 K. It is suggested that the breakdown of the normal-mode picture implies that the average crystal structure may not be a proper starting point to understand the electronic properties of the crystal. In addition to our main findings, an unreported phase of Cs2AgBiBr6 is also discovered below approximate to 37 K.