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  • 1.
    Abrikosov, Igor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Liot, Francois
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Smirnova, E. A.
    Theoretical Physics Department, Moscov Steel and Alloys Institute, Moscow, Russia.
    Magnetism in systems with reduced dimensionality and chemical disorder: the local environment effects2006In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 300, no 1, p. 211-215Article in journal (Refereed)
    Abstract [en]

    We study influence of the local chemical environment, the so-called local environment effects, on the electronic structure and properties of magnetic systems with reduced dimensionality and chemical disorder, and show that they play a crucial role in a vicinity of magnetic instability. As a model, we consider Fe–Ni Invar. We present results obtained from ab initio calculations of the electronic structure, magnetic moments, and exchange interactions in random fcc Fe–Ni alloy, for a single monolayer alloy film on a Cu (0 0 1) substrate as well as in the bulk. We analyze the difference between the film and the bulk magnetization, which is found to be most pronounced for dilute alloys. We also analyze a sensitivity of the individual magnetic moments and effective exchange parameters to the local chemical environment of the atoms.

  • 2.
    Abrikosov, Igor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Olovsson, Weine
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden.
    Local environment effects in random metallic alloys2005In: The Science of Complex Alloy Phases: proceedings of a symposium held during the TMS Annual Meeting and Exhibition in San Francisco, California, USA, February 13-17, 2005, to honor the Wiliam Hume-Rothery Award recipient Professor Uichiro Mizutani / [ed] Thaddeus B. Massalski and Patrice E. A. Turchi, USA: TMS , 2005, 1, p. 87-108Chapter in book (Other academic)
    Abstract [en]

    This book is published in honor of the 2005 Hume-Rothery Award Recipient, Uichiro Mizutani. It emphasizes both theoretical and experimental aspects of electronic, structural, and thermodynamic properties of complex alloy phases. Leading experts provide an assessment of our current understanding of the structural properties of complex materials, including quasicrystalline and amorphous alloys. Special emphasis is placed on our understanding of why nature is able to stabilize complex atomic arrangements and on recent results related to structurally complex alloy phases. These topics, in the spirit of the work carried out by U. Mizutani, constitute the main theme of the book

  • 3.
    Abrikosov, Igor
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Marten, Tobias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Olsson, P.
    Uppsala University.
    Simak, Sergey
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Electronic theory of materials properties: from fundamental understanding towards materials design2006Report (Other academic)
    Abstract [en]

           

  • 4.
    Alling, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Effect of magnetic disorder and strong electron correlations on the thermodynamics of CrN2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, p. 184430-Article in journal (Refereed)
    Abstract [en]

    Two different methods for the modeling of a magnetically disordered CrN stateusing a supercell approach are investigated. They are found to give equivalentresults of the total energy, being also similar to results obtained with an effectivemedium approach. Furthermore, CrN is shown to be better described using aLDA+U framework for the treatment of electron-electron correlations as comparedto GGA or LDA calculations. Modeling the cubic paramagnetic phase with ourmodels for magnetic disorder and considering the strong electron correlations, thetemperature and pressure induced phase transitions in CrN can be explained.

  • 5.
    Alling, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Questionable collapse of the bulk modulus in CrN2010In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 9, no 4, p. 283-284Article in journal (Other academic)
    Abstract [en]

    In this comment we show that the main conclusion in a previous article, claiminga drastic increase in compressibility of CrN at the cubic to orthorhombic phasetransition, is unsupported by first-principles calculations. We show that if thecubic CrN phase is considered as a disordered magnetic material, as supported bydifferent experimental data, rather then non-magnetic, the bulk modulus is almostunaffected by the transition.

  • 6.
    Alling, Björn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Marten, Tobias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Abrikosov, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Karimi, A.
    Swiss Federal Institute of Technology Lausanne, Switzerland.
    Comparison of thermodynamic properties of cubic Cr 1-x Al x N and Ti 1-x Al x N from first-principles calculations2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, no 044314Article in journal (Refereed)
    Abstract [en]

    In order to investigate the stability of the cubic phase of Cr1−xAlxN at high AlN content, first principles calculations of magnetic properties, lattice parameters, electronic structure, and mixing enthalpies of the system were performed. The mixing enthalpy was calculated on a fine concentration mesh to make possible the accurate determination of its second concentration derivative. The results are compared to calculations performed for the related compound Ti1−xAlxN and with experiments. The mixing enthalpy is discussed in the context of isostructural spinodal decomposition. It is shown that the magnetism is the key to understand the difference between the Cr- and Ti-containing systems. Cr1−xAlxN turns out to be more stable against spinodal decomposition than Ti1−xAlxN, especially for AlN-rich samples which are of interest in cutting tools applications.

  • 7.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Theoretical Considerations of Local Environment Effects in Alloys2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is devoted to a theoretical study of local environment effects in alloys. A fundamental property of a disordered system is that all chemically equivalent atoms are different due to their different chemical environments, in contrast to an ideal periodic solid where all the atoms that occupy equivalent positions in the crystal have exactly the same physical properties. The local environment effects have been largely ignored in earlier theories of disordered systems, that is the system has been treated as a whole and average properties have been derived. Moreover, inhomogeneous systems, such as surfaces and interfaces, induce local environment effects that are not necessarily present in the bulk.

    The importance and presence of local environment effects are illustrated by calculating observable physical properties in various systems. In particular, by employing the complete screening picture the effects of local environments on the core-level binding energy shifts as well as Auger shifts in random alloys are in- vestigated. This so-called disorder broadening effect has recently been observed experimentally. It is shown that there are different contributions to the disorder broadening that vary with the local chemical environment. Furthermore, the influ- ence of inhomogeneous lattice distortions on the disorder broadening of the core- level photoemission spectra are considered for systems with large size-mismatch between the alloy components.

    The effects of local chemical environments on physical properties in magnetic systems are illuminated. A noticeable variation in the electronic structure, local magnetic moments and exchange parameters at different sites is obtained. This reflects the sensitivity to different chemical environments and it is shown to be of qualitative importance in the vicinity of magnetic instability.

    The local environment effects due to the presence of surfaces and interfaces are also considered. The effect is explicitly studied by considering the concentration profile of a thin Ag-Pd film deposited on a Ru substrate. Two computational approaches are utilized to calculate the relative composition in each layer of the thin film as a function of temperature in a theoretically consistent way. It is shown that, opposed to the situation in the bulk, where a complete solubility between Ag and Pd takes place, a non-uniform distribution of the alloy components across the film is observed.

    In another study it is investigated whether the presence of TiN interfaces changes the dynamical and thermodynamic stability of B1 SiN. Phonon calcula- tions show that TiN interfaces have a stabilization effect on the lattice dynamics. On the other hand, calculations of the Si vacancy formation energy show that the structures are unstable with respect to composition variations.

     

    List of papers
    1. Ab initio study of disorder broadening of core photoemission spectra in random Cu-Pd and Ag-Pd alloys
    Open this publication in new window or tab >>Ab initio study of disorder broadening of core photoemission spectra in random Cu-Pd and Ag-Pd alloys
    2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 5Article in journal (Refereed) Published
    Abstract [en]

    A first-principles study of the effect of local environment on the electronic structure of random face-centered cubic Ag-Pd and Cu-Pd alloys is presented. The core-level shift for each atom in the equiatomic alloys is calculated and compared to experimental data. It is shown how the initial-state and final-state distributions contribute to the total broadening. We find that the initial-state and the final-state contributions together increase the broadening for the investigated core levels in Cu and Ag, whereas they cancel each other to a large degree for Pd. We also demonstrated how local lattice relaxations influence the binding energy shift. We find that relaxation does not influence the average shift, though it is able to affect the broadening of the simulated x-ray photoelectron spectroscopy spectra. © 2005 The American Physical Society.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-29016 (URN)10.1103/PhysRevB.72.054210 (DOI)14255 (Local ID)14255 (Archive number)14255 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    2. Local environment effects in random metallic alloys
    Open this publication in new window or tab >>Local environment effects in random metallic alloys
    2005 (English)In: The Science of Complex Alloy Phases: proceedings of a symposium held during the TMS Annual Meeting and Exhibition in San Francisco, California, USA, February 13-17, 2005, to honor the Wiliam Hume-Rothery Award recipient Professor Uichiro Mizutani / [ed] Thaddeus B. Massalski and Patrice E. A. Turchi, USA: TMS , 2005, 1, p. 87-108Chapter in book (Other academic)
    Abstract [en]

    This book is published in honor of the 2005 Hume-Rothery Award Recipient, Uichiro Mizutani. It emphasizes both theoretical and experimental aspects of electronic, structural, and thermodynamic properties of complex alloy phases. Leading experts provide an assessment of our current understanding of the structural properties of complex materials, including quasicrystalline and amorphous alloys. Special emphasis is placed on our understanding of why nature is able to stabilize complex atomic arrangements and on recent results related to structurally complex alloy phases. These topics, in the spirit of the work carried out by U. Mizutani, constitute the main theme of the book

    Place, publisher, year, edition, pages
    USA: TMS, 2005 Edition: 1
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-24462 (URN)6574 (Local ID)0-87339-593-X (ISBN)978-0-87339-593-9 (ISBN)6574 (Archive number)6574 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-09-26Bibliographically approved
    3. Core-level shifts in complex metallic systems from first principle
    Open this publication in new window or tab >>Core-level shifts in complex metallic systems from first principle
    2006 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 11, p. 2447-2464Article in journal (Refereed) Published
    Abstract [en]

    We show that core-level binding energy shifts (CLS) can be reliably calculated within density functional theory. The scheme includes both the initial (electron energy eigenvalue) as well as final state (relaxation due to core-hole screening) effects in the same framework. The results include CLS as a function of composition in substitutional random bulk and surface alloys. Sensitivity of the CLS to the local chemical environment in the bulk and at the surface is demonstrated. A possibility to use the CLS for structural determination is discussed. Finally, an extension of the model is made for Auger kinetic energy shift calculations.

    Place, publisher, year, edition, pages
    Wiley, 2006
    Keywords
    71.15.-m, 71.23.-k, 79.20.Fv, 79.60.Dp, 79.60.Ht, 79.60.Jv
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-37239 (URN)10.1002/pssb.200642165 (DOI)34061 (Local ID)34061 (Archive number)34061 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    4. Suppression of disorder broadening of core-level photoelectron lines in CuAu alloys by inhomogeneous lattice distortion
    Open this publication in new window or tab >>Suppression of disorder broadening of core-level photoelectron lines in CuAu alloys by inhomogeneous lattice distortion
    Show others...
    2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 1, p. 012201-Article in journal (Refereed) Published
    Abstract [en]

    Disorder broadening of core-level binding energies is a general effect observed in random alloys, and identifies an opportunity for studying specific local environments experimentally. Here we study it in an archetypical system: face-centered-cubic Cu50Au50. While the disorder broadening is clearly detectable at Au, at Cu it is below the detection limit. We supplement experiments by a theoretical study where we model the alloy by a large supercell constructed as a special quasirandom structure and calculate binding-energy shifts at all sites in the supercell. Theory shows that the suppression of the disorder broadening at Cu results from a delicate balance between the influence of local chemical environment and inhomogeneous lattice distortions on the site-resolved core-level shifts. Surprisingly, even larger relaxation-induced shifts are observed at Au sites.

    Keywords
    copper alloys, core levels, electronic structure, gold alloys, photoelectron spectra
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-16832 (URN)10.1103/PhysRevB.79.012201 (DOI)
    Available from: 2009-02-21 Created: 2009-02-20 Last updated: 2017-12-13Bibliographically approved
    5. First principle calculations of core-level binding energy and Auger kinetic energy shifts in metallic solids
    Open this publication in new window or tab >>First principle calculations of core-level binding energy and Auger kinetic energy shifts in metallic solids
    Show others...
    2010 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 178, no Sp. Iss. SI, p. 88-99Article in journal (Refereed) Published
    Abstract [en]

    We present a brief overview of recent theoretical studies of the core-level binding energy shift (CLS) in solid metallic materials. The focus is on first principles calculations using the complete screening picture, which incorporates the initial (ground state) and final (core-ionized) state contributions of the electron photoemission process in X-ray photoelectron spectroscopy (XPS), all within density functional theory (DFT). Considering substitutionally disordered binary alloys, we demonstrate that on the one hand CLS depend on average conditions, such as volume and overall composition, while on the other hand they are sensitive to the specific local atomic environment. The possibility of employing layer resolved shifts as a tool for characterizing interface quality in fully embedded thin films is also discussed, with examples for CuNi systems. An extension of the complete screening picture to core-core-core Auger transitions is given, and new results for the influence of local environment effects on Auger kinetic energy shifts in fcc AgPd are presented.

    Place, publisher, year, edition, pages
    Elsevier Science B.V., Amsterdam., 2010
    Keywords
    Core-level shift, Disordered materials, Metallic alloys, Auger kinetic energy
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-57401 (URN)10.1016/j.elspec.2009.10.007 (DOI)000278295900006 ()
    Note
    Original Publication: Weine Olovsson, Tobias Marten, Erik Holmstrom, Borje Johansson and Igor Abrikosov, First principle calculations of core-level binding energy and Auger kinetic energy shifts in metallic solids, 2010, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, (178), Sp. Iss. SI, 88-99. http://dx.doi.org/10.1016/j.elspec.2009.10.007 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2017-12-12Bibliographically approved
    6. Magnetism in systems with reduced dimensionality and chemical disorder: the local environment effects
    Open this publication in new window or tab >>Magnetism in systems with reduced dimensionality and chemical disorder: the local environment effects
    2006 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 300, no 1, p. 211-215Article in journal (Refereed) Published
    Abstract [en]

    We study influence of the local chemical environment, the so-called local environment effects, on the electronic structure and properties of magnetic systems with reduced dimensionality and chemical disorder, and show that they play a crucial role in a vicinity of magnetic instability. As a model, we consider Fe–Ni Invar. We present results obtained from ab initio calculations of the electronic structure, magnetic moments, and exchange interactions in random fcc Fe–Ni alloy, for a single monolayer alloy film on a Cu (0 0 1) substrate as well as in the bulk. We analyze the difference between the film and the bulk magnetization, which is found to be most pronounced for dilute alloys. We also analyze a sensitivity of the individual magnetic moments and effective exchange parameters to the local chemical environment of the atoms.

    Place, publisher, year, edition, pages
    Elsevier, 2006
    Keywords
    Local environment effects, Invar alloys, First-principles calculations
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17428 (URN)10.1016/j.jmmm.2005.10.065 (DOI)
    Available from: 2009-03-24 Created: 2009-03-24 Last updated: 2017-12-13
    7. Double-segregation effect in AgxPd1−x /Ru(0001) thin film nanostructures
    Open this publication in new window or tab >>Double-segregation effect in AgxPd1−x /Ru(0001) thin film nanostructures
    Show others...
    2008 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, p. 125406-1-125406-7Article in journal (Refereed) Published
    Abstract [en]

    We study the structural properties of ultrathin AgxPd1−x films on top of a Ru(0001) substrate. Effective interatomic interactions, obtained from first-principles calculations, have been used in Monte Carlo simulations to derive the distribution of the alloy components in a four-monolayer (4-ML) Ag-Pd film. Though Ag-Pd alloys show complete solubility in the bulk, the thin film geometry leads to a pronounced segregation between Ag and Pd atoms with a strong preference of Ag atoms toward the surface and Pd atoms toward the interface. The theoretical prediction of this double-segregation effect is strongly supported by photoelectron spectroscopy experiments carried out for 4-ML thin films. We also show, in an additional experiment, that even in the case where initially 1 ML Ag is buried under 6 ML Pd, the whole Ag ML segregates to the surface.

    Place, publisher, year, edition, pages
    APS, 2008
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-44362 (URN)10.1103/PhysRevB.77.125406 (DOI)76396 (Local ID)76396 (Archive number)76396 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
    8. Single-monolayer SiNx embedded in TiN: A first-principles study
    Open this publication in new window or tab >>Single-monolayer SiNx embedded in TiN: A first-principles study
    Show others...
    2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 21, p. 212102-Article in journal (Refereed) Published
    Abstract [en]

    The dynamical and thermodynamic stability of a single monolayer of SiNx sandwiched isostructurally between B1-TiN(001) and (111) oriented slabs are investigated by means of density functional theory. Possible dynamical stabilization of the (001) interface, by distortion of the Si-N bonds, is considered and found to almost, but not completely, remove the phonon instabilities. The (111) interface on the other hand is found to be dynamically stable. We furthermore relax the stoichiometry degree of freedom by allowing for Si vacancies in the lattice and show that the ideal 1:1 SiN stoichiometry in both interfaces are thermodynamically unstable with respect to Si vacancy formation regardless if the system is grown under nitrogen-rich or nitrogen-poor conditions, and therefore ruling out its relevance for performance of real materials.

    Place, publisher, year, edition, pages
    American Physical Society, 2010
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-58256 (URN)10.1103/PhysRevB.81.212102 (DOI)000279381800001 ()
    Note
    Original Publication: Tobias Marten, Eyvas Isaev, Björn Alling, Lars Hultman and Igor Abrikosov, Single-monolayer SiNx embedded in TiN: A first-principles study, 2010, Physical Review B. Condensed Matter and Materials Physics, (81), 21, 212102. http://dx.doi.org/10.1103/PhysRevB.81.212102 Copyright: American Physical Society http://www.aps.org/ Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12Bibliographically approved
  • 8.
    Marten, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Olovsson, W
    Kyoto University.
    Johansson, B
    Uppsala University.
    Cole, R J
    University Edinburgh.
    Beamson, G
    STFC Daresbury Laboratory, Warrington.
    Haines, S R
    University of Liverpool.
    Weightman, P
    University of Liverpool.
    Suppression of disorder broadening of core-level photoelectron lines in CuAu alloys by inhomogeneous lattice distortion2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 1, p. 012201-Article in journal (Refereed)
    Abstract [en]

    Disorder broadening of core-level binding energies is a general effect observed in random alloys, and identifies an opportunity for studying specific local environments experimentally. Here we study it in an archetypical system: face-centered-cubic Cu50Au50. While the disorder broadening is clearly detectable at Au, at Cu it is below the detection limit. We supplement experiments by a theoretical study where we model the alloy by a large supercell constructed as a special quasirandom structure and calculate binding-energy shifts at all sites in the supercell. Theory shows that the suppression of the disorder broadening at Cu results from a delicate balance between the influence of local chemical environment and inhomogeneous lattice distortions on the site-resolved core-level shifts. Surprisingly, even larger relaxation-induced shifts are observed at Au sites.

  • 9.
    Marten, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Isaev, Eyvas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Lind, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    First-principles study of the SiNx/TiN(001) interface2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, no 10, p. 104106-Article in journal (Refereed)
    Abstract [en]

    The structure of the SiNx tissue phase in superhard TiN/SiNx nanocomposites has been debated in the literature. We present a theoretical investigation of the possibility of crystalline and coherent ( 001) interfaces that satisfies the two necessary criteria, stability with respect to lattice vibrations as well as to variations in stoichiometry. It is found that one monolayer of Si tetrahedrally coordinated by N in a B3-like geometry embedded between B1-TiN( 001) surfaces is both dynamically stable and thermodynamically stable with respect to vacancy formation. However, with increasing layer thickness the B3-type structure becomes unstable with respect to Si vacancy formation. Instead we suggest that a tetragonal D0(22)-like order of Si vacancies can stabilize the interface. These structures are in line with the experimental findings of the crystalline tissue phase which has coherent interfaces with TiN.

  • 10.
    Marten, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Ruban, Andrei V.
    Department of Materials Science and Engineering Royal Institute of Technology, Stockholm.
    Olovsson, Weine
    Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan.
    Kramer, Charlotte
    Department of Physics and Nanotechnology Aalborg University, Aalborg, Denmark.
    Godowski, Jan P.
    Institute of Experimental Physics, University of Wroclaw, 50-204 Wroclaw, Poland.
    Bech, Lone
    Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg East, Denmark.
    Li, Zheshen
    Institute of Storage Ring Facilities, University of Aarhus, DK-8000 Aarhus, Denmark.
    Onsgaard, Jens
    Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg East, Denmark.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Double-segregation effect in AgxPd1−x /Ru(0001) thin film nanostructures2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, p. 125406-1-125406-7Article in journal (Refereed)
    Abstract [en]

    We study the structural properties of ultrathin AgxPd1−x films on top of a Ru(0001) substrate. Effective interatomic interactions, obtained from first-principles calculations, have been used in Monte Carlo simulations to derive the distribution of the alloy components in a four-monolayer (4-ML) Ag-Pd film. Though Ag-Pd alloys show complete solubility in the bulk, the thin film geometry leads to a pronounced segregation between Ag and Pd atoms with a strong preference of Ag atoms toward the surface and Pd atoms toward the interface. The theoretical prediction of this double-segregation effect is strongly supported by photoelectron spectroscopy experiments carried out for 4-ML thin films. We also show, in an additional experiment, that even in the case where initially 1 ML Ag is buried under 6 ML Pd, the whole Ag ML segregates to the surface.

  • 11.
    Marten, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Isaev, Eyvas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Single-monolayer SiNx embedded in TiN: A first-principles study2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 21, p. 212102-Article in journal (Refereed)
    Abstract [en]

    The dynamical and thermodynamic stability of a single monolayer of SiNx sandwiched isostructurally between B1-TiN(001) and (111) oriented slabs are investigated by means of density functional theory. Possible dynamical stabilization of the (001) interface, by distortion of the Si-N bonds, is considered and found to almost, but not completely, remove the phonon instabilities. The (111) interface on the other hand is found to be dynamically stable. We furthermore relax the stoichiometry degree of freedom by allowing for Si vacancies in the lattice and show that the ideal 1:1 SiN stoichiometry in both interfaces are thermodynamically unstable with respect to Si vacancy formation regardless if the system is grown under nitrogen-rich or nitrogen-poor conditions, and therefore ruling out its relevance for performance of real materials.

  • 12.
    Marten, Tobias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Simak, Sergey
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Olovsson, Weine
    Department of Physics Uppsala University.
    Abrikosov, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Ab initio study of disorder broadening of core photoemission spectra in random Cu-Pd and Ag-Pd alloys2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 5Article in journal (Refereed)
    Abstract [en]

    A first-principles study of the effect of local environment on the electronic structure of random face-centered cubic Ag-Pd and Cu-Pd alloys is presented. The core-level shift for each atom in the equiatomic alloys is calculated and compared to experimental data. It is shown how the initial-state and final-state distributions contribute to the total broadening. We find that the initial-state and the final-state contributions together increase the broadening for the investigated core levels in Cu and Ag, whereas they cancel each other to a large degree for Pd. We also demonstrated how local lattice relaxations influence the binding energy shift. We find that relaxation does not influence the average shift, though it is able to affect the broadening of the simulated x-ray photoelectron spectroscopy spectra. © 2005 The American Physical Society.

  • 13.
    Olovsson, Weine
    et al.
    Kyoto University, Sakyo Kyoto.
    Asker, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Core-level shifts in complex metallic systems from first principle2006In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 11, p. 2447-2464Article in journal (Refereed)
    Abstract [en]

    We show that core-level binding energy shifts (CLS) can be reliably calculated within density functional theory. The scheme includes both the initial (electron energy eigenvalue) as well as final state (relaxation due to core-hole screening) effects in the same framework. The results include CLS as a function of composition in substitutional random bulk and surface alloys. Sensitivity of the CLS to the local chemical environment in the bulk and at the surface is demonstrated. A possibility to use the CLS for structural determination is discussed. Finally, an extension of the model is made for Auger kinetic energy shift calculations.

  • 14.
    Olovsson, Weine
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Holmstroem, Erik
    University Austral Chile.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Niklasson, Anders M N
    Los Alamos National Laboratory.
    Interface core-level shifts as a probe of embedded thin-film quality2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 8, p. 085431-Article in journal (Refereed)
    Abstract [en]

    We use first-principles calculations of layer-resolved core-level binding energy shifts (CLSs) within density functional theory as away to characterize the interface quality and thickness in embedded thin-film nanomaterials. A closer study of interfaces is motivated as properties specific to nanostructures can be related directly to the interface environment or indirectly as interference effects due to quantum confinement. From an analysis based on the Cu 2p(3/2) CLS for Cu embedded in Ni and Co fcc (100) and Fe bcc (100), with the interfaces represented by intermixing profiles controlled by a single parameter, we evaluate layer-resolved shifts as a probe of the thin-film quality. The core-level shifts in the corresponding disordered alloys, as well as local environment effects, are studied for comparison. We also discuss the possibility of detecting interface states by means of core-level shift measurements.

  • 15.
    Olovsson, Weine
    et al.
    Department of Materials Science and Engineering, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Japan.
    Marten, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Holmstrom, Erik
    Instituto de Física, Universidad Austral de Chile, Valdivia, Chile.
    Johansson, Borje
    Department of Physics and Materials Science, Uppsala University, P.O. Box 530, SE-751 21 Uppsala, Sweden.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    First principle calculations of core-level binding energy and Auger kinetic energy shifts in metallic solids2010In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 178, no Sp. Iss. SI, p. 88-99Article in journal (Refereed)
    Abstract [en]

    We present a brief overview of recent theoretical studies of the core-level binding energy shift (CLS) in solid metallic materials. The focus is on first principles calculations using the complete screening picture, which incorporates the initial (ground state) and final (core-ionized) state contributions of the electron photoemission process in X-ray photoelectron spectroscopy (XPS), all within density functional theory (DFT). Considering substitutionally disordered binary alloys, we demonstrate that on the one hand CLS depend on average conditions, such as volume and overall composition, while on the other hand they are sensitive to the specific local atomic environment. The possibility of employing layer resolved shifts as a tool for characterizing interface quality in fully embedded thin films is also discussed, with examples for CuNi systems. An extension of the complete screening picture to core-core-core Auger transitions is given, and new results for the influence of local environment effects on Auger kinetic energy shifts in fcc AgPd are presented.

1 - 15 of 15
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