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  • 1.
    Ahrén, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Selegård, Linnéa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8Article in journal (Refereed)
    Abstract [en]

    Chelated gadolinium ions, e. g., GdDTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd2O3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r(1) and r(2) values almost as high as those for free Gd3+ ions in water. The Gd2O3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.

  • 2.
    Ahrén, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Nordblad, Per
    Division of Solid State Physics, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    One-step synthesis of sub 5 nm sized manganese oxide based nanoparticles2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Sub 5 nm sized manganese oxide nanoparticles; MnOx (1 ≤ x ≤ 2), were synthesized via a short time room temperature synthesis route. The nanoparticles are crystalline, spherically shaped and in the size range of 2-4 nm as shown by transmission electron microscopy studies. Selected area electron diffraction patterns were collected and their appearance indicated that the nanoparticle cores are composed of MnO. Also, co-existence of the (II) and (III) oxidation states at the nanoparticle surface was verified by results achieved from infrared spectroscopy and X-ray photoelectron spectroscopy. These measurements also supported presence of a minor amount of acetate groups as well as a negligible fraction of carbonate groups at the nanoparticle surfaces. The interpretation of the IR spectra was confirmed by quantum chemical calculations using the high spin manganese nanoparticle Mn12O12(OAc)16(H2O)4, as a model system for the MnOx nanoparticle surface. Bulk MnO and Mn2O3 are known to be antiferromagnetic. The magnetic properties are however somewhat dependent of the crystallite size and changes when scaling down to the nanoregion. The MnOx (1 ≤ x ≤ 2) nanoparticles investigated in this work show a superparamagnetic behavior with a blocking temperature of approximately 12 K proven by means of SQUID measurements. The relaxivities of the nanoparticles and the Mn(OAc)2 precursors were studied with a bench top NMR analyzer verifying nanoparticle r1 and r2 of 0.5 and 6 mMs-1 respectively. The r1 relaxivity is lower than what is earlier reported for Gd based contrast agent, but improvements are expected by further surface modification, due to increased rotational time and higher water dispersability.

  • 3.
    Aidas, Kestutis
    et al.
    Vilnius University, Lithuania .
    Angeli, Celestino
    University of Ferrara, Italy .
    Bak, Keld L.
    University of Aarhus, Denmark .
    Bakken, Vebjorn
    University of Oslo, Norway .
    Bast, Radovan
    KTH Royal Institute Technology, Sweden .
    Boman, Linus
    EMGS ASA, Norway .
    Christiansen, Ove
    University of Aarhus, Denmark .
    Cimiraglia, Renzo
    University of Ferrara, Italy .
    Coriani, Sonia
    University of Trieste, Italy .
    Dahle, Pal
    Norwegian Comp Centre, Norway .
    Dalskov, Erik K.
    Systematic, Denmark .
    Ekstrom, Ulf
    University of Oslo, Norway .
    Enevoldsen, Thomas
    University of So Denmark, Denmark .
    Eriksen, Janus J.
    University of Aarhus, Denmark .
    Ettenhuber, Patrick
    University of Aarhus, Denmark .
    Fernandez, Berta
    University of Santiago de Compostela, Spain University of Santiago de Compostela, Spain .
    Ferrighi, Lara
    UiT Arctic University of Norway, Norway .
    Fliegl, Heike
    University of Oslo, Norway .
    Frediani, Luca
    UiT Arctic University of Norway, Norway .
    Hald, Kasper
    Danske Bank, Denmark .
    Halkier, Asger
    CSC Scandihealth, Denmark .
    Hattig, Christof
    Ruhr University of Bochum, Germany .
    Heiberg, Hanne
    Norwegian Meteorol Institute, Norway .
    Helgaker, Trygve
    University of Oslo, Norway .
    Christian Hennum, Alf
    Norwegian Def Research Estab, Norway .
    Hettema, Hinne
    University of Auckland, New Zealand .
    Hjertenaes, Eirik
    Norwegian University of Science and Technology, Norway .
    Host, Stinne
    University of Aarhus, Denmark .
    Hoyvik, Ida-Marie
    University of Aarhus, Denmark .
    Francesca Iozzi, Maria
    University of Oslo, Norway .
    Jansik, Branislav
    Technical University of Ostrava, Czech Republic .
    Jorgen Aa. Jensen, Hans
    University of So Denmark, Denmark .
    Jonsson, Dan
    UiT Arctic University of Norway, Norway .
    Jorgensen, Poul
    University of Aarhus, Denmark .
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Kirpekar, Sheela
    KVUC, Denmark .
    Kjrgaard, Thomas
    University of Aarhus, Denmark .
    Klopper, Wim
    Karlsruhe Institute Technology, Germany .
    Knecht, Stefan
    Swiss Federal Institute Technology, Switzerland .
    Kobayashi, Rika
    Australian National University, Australia .
    Koch, Henrik
    Norwegian University of Science and Technology, Norway .
    Kongsted, Jacob
    University of So Denmark, Denmark .
    Krapp, Andreas
    Jotun AS, Norway .
    Kristensen, Kasper
    University of Aarhus, Denmark .
    Ligabue, Andrea
    University of Modena and Reggio Emilia, Italy .
    B. Lutnaes, Ola
    Cisco Syst, Norway .
    I. Melo, Juan
    University of Buenos Aires, Argentina University of Buenos Aires, Argentina .
    V. Mikkelsen, Kurt
    University of Copenhagen, Denmark .
    H. Myhre, Rolf
    Norwegian University of Science and Technology, Norway .
    Neiss, Christian
    University of Erlangen Nurnberg, Germany .
    B. Nielsen, Christian
    Sun Chemistry, Denmark .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Olsen, Jeppe
    University of Aarhus, Denmark University of So Denmark, Denmark .
    Magnus H. Olsen, Jogvan
    University of Aarhus, Denmark University of So Denmark, Denmark .
    Osted, Anders
    Koge Gymnasium, Denmark .
    J. Packer, Martin
    University of So Denmark, Denmark .
    Pawlowski, Filip
    Kazimierz Wielki University, Poland .
    B. Pedersen, Thomas
    University of Oslo, Norway .
    F. Provasi, Patricio
    Northeastern University, Argentina IMIT CONICET, Argentina .
    Reine, Simen
    University of Oslo, Norway .
    Rinkevicius, Zilvinas
    KTH Royal Institute Technology, Sweden KTH Royal Institute Technology, Sweden .
    A. Ruden, Torgeir
    Kjeller Software Commun, Norway .
    Ruud, Kenneth
    UiT Arctic University of Norway, Norway .
    V. Rybkin, Vladimir
    Karlsruhe Institute Technology, Germany .
    Salek, Pawel
    PSS9 Dev, Poland .
    C. M. Samson, Claire
    Karlsruhe Institute Technology, Germany .
    Sanchez de Meras, Alfredo
    University of Valencia, Spain .
    Saue, Trond
    University of Toulouse 3, France .
    P. A. Sauer, Stephan
    University of Copenhagen, Denmark .
    Schimmelpfennig, Bernd
    Karlsruhe Institute Technology, Germany .
    Sneskov, Kristian
    Danske Bank, Denmark .
    H. Steindal, Arnfinn
    UiT Arctic University of Norway, Norway .
    O. Sylvester-Hvid, Kristian
    Danish Technology Institute Nano and Microtechnol Prod, Denmark .
    R. Taylor, Peter
    University of Melbourne, Australia University of Melbourne, Australia .
    M. Teale, Andrew
    University of Nottingham, England .
    I. Tellgren, Erik
    University of Oslo, Norway .
    P. Tew, David
    University of Bristol, England .
    J. Thorvaldsen, Andreas
    University of Aarhus, Denmark .
    Thogersen, Lea
    CLC bio, Denmark .
    Vahtras, Olav
    KTH Royal Institute Technology, Sweden .
    A. Watson, Mark
    Princeton University, NJ 08544 USA .
    J. D. Wilson, David
    La Trobe University, Australia La Trobe University, Australia .
    Ziolkowski, Marcin
    Clemson University, SC USA .
    Agren, Hans
    KTH Royal Institute Technology, Sweden .
    The Dalton quantum chemistry program system2014In: WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE, ISSN 1759-0876, Vol. 4, no 3, p. 269-284Article in journal (Refereed)
    Abstract [en]

    Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.

  • 4.
    Al-Saidi, W A
    et al.
    University of Pittsburgh, USA .
    Asher, Sanford A
    University of Pittsburgh, USA .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Resonance Raman Spectra of TNT and RDX Using Vibronic Theory, Excited-State Gradient, and Complex Polarizability Approximations2012In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 116, no 30, p. 7862-7872Article in journal (Refereed)
    Abstract [en]

    Geometries, UV absorption bands, and resonance Raman (RR) cross sections of TNT and RDX are investigated using density functional theory (DFT) in conjunction with the Coulomb attenuated B3LYP exchange-correlation functional. The absorption and RR spectra are determined with use of vibronic (VB) theory, excited-state gradient, and complex polarizability (CPP) approximations. We examined lowenergy isomers (two for TNT and four for RDX) whose energies differ by less than 1 kcal/mol, such that they would appreciably be populated at room temperature. The two TNT isomers differ by an internal rotation of the methyl group, while the four conformers of RDX differ by the arrangements of the nitro group relative to the ring. Our theoretical optical properties of the TNT and RDX isomers are in excellent agreement with experimental and recent CCSD-EOM results, respectively. For the two TNT isomers, the ultraviolet RR (UVRR) spectra are similar and in good agreement with recently measured experimental results. Additionally, the UVRR spectra computed using the excited-state and CPP approaches compare favorably with the VB theory results. On the other hand, the RR spectra of the RDX conformers differ from one another, reflecting the importance of the positioning of the NO2 groups with respect to the ring. In the gas phase or in solution, RDX would give a spectrum associated with a conformationally averaged structure. It is encouraging that the computed spectra of the conformers show similarities to recent measured RDX spectra in acetonitrile solution, and reproduce the 10-fold decrease in the absolute Raman cross sections of RDX compared to TNT for the observed 229 nm excitation. We show that in TNT and RDX vibrational bands that couple to NO2 or the ring are particularly resonance enhanced. Finally, the computed RDX spectra of the conformers present a benchmark for understanding the RR spectra of the solid-phase polymorphs of RDX.

  • 5.
    Baev, Alexander
    et al.
    Institute for lasers, Photonics and Biophotonics SUNY at Buffalo, USA.
    Henriksson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Ågren, Hans
    KTH, Stockholm.
    A quantum mechanical - Electrodynamical approach to nonlinear properties: Application to optical power limiting with platinum-organic compounds2007In: Journal of nonlinear optical physics and materials, ISSN 0218-8635, Vol. 16, no 2, p. 157-169Article in journal (Refereed)
    Abstract [en]

    Light propagation in a medium is sensitively dependent on the shape and intensity of the optical pulse as well as on the electronic and vibrational structure of the basic molecular units. We review in this paper the results of systematic studies of this problem for isotropic media. Our theoretical approach - the quantum mechanical-electrodynamical (QMED) approach - is based on a quantum mechanical account of the many-level electron-nuclear medium coupled to a numerical solution of the density matrix and Maxwell's equations. This allows us to accommodate a variety of nonlinear effects which accomplish the propagation of strong light pulses. Particular attention is paid to the understanding of the role of coherent and sequential excitations of electron-nuclear degrees of freedom. The QMED combination of quantum chemistry with classical pulse propagation enables us to estimate the optical transmission from cross sections of multi-photon absorption processes and from considerations of propagation effects, saturation and pulse effects. Results of the theory suggest that in the nonlinear regime, it is often necessary to simultaneously account for coherent one-step and incoherent step-wise multi-photon absorption, as well as for off-resonant excitations even when resonance conditions prevail. The dynamic theory of nonlinear propagation of a few interacting intense light pulses is highlighted here in a study of the optical power limiting with platinum-organic molecular compounds. © World Scientific Publishing Company.

  • 6.
    Baev, Alexander
    et al.
    Institute for Lasers, Photonics and Biophotonics, SUNY at Buffalo, Buffalo, New York .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Henriksson, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Ågren, Hans
    Theoretical Chemistry, Royal Institute of Technology, Stockholm.
    Theoretical Simulations of Clamping Levels in Optical Power Limiting2006In: Journal of Physical Chemistry B, ISSN 1520-5215, Vol. 110, no 42, p. 20912-20916Article in journal (Refereed)
    Abstract [en]

    Multiphysics modeling, combining quantum mechanical and classical wave mechanical theories, of clamping levels has been performed for a platinum(II) organic compound in a sol−gel glass matrix. A clamping level of 2.5 μJ is found for a pulse duration of 10 ns. The excited-state absorption in the triplet manifold is shown to be crucial for clamping to occur.

  • 7.
    Bast, Radovan
    et al.
    CNRS.
    Saue, Trond
    CNRS.
    Henriksson, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman , Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Role of noncollinear magnetization for the first-order electric-dipole hyperpolarizability at the four-component Kohn-Sham density functional theory level2009In: JOURNAL OF CHEMICAL PHYSICS, ISSN 0021-9606 , Vol. 130, no 2, p. 024109-Article in journal (Refereed)
    Abstract [en]

    The quadratic response function has been derived and implemented at the adiabatic four-component Kohn-Sham density functional theory level with inclusion of noncollinear spin magnetization and gradient corrections in the exchange-correlation functional-a work that is an extension of our previous report where magnetization dependencies in the exchange-correlation functional were ignored [J. Henriksson, T. Saue, and P. Norman, J. Chem. Phys. 128, 024105 (2008)]. The electric-field induced second-harmonic generation experiments on CF3Cl and CF3Br are addressed by a determination of (beta) over bar (-2 omega;omega,omega) for a wavelength of 694.3 nm, and the same property is also determined for CF3I. The relativistic effects on the static hyperpolarizability for the series of molecules amount to 1%, 5%, and 9%, respectively. At the experimental wavelength, the contributions to beta due to the magnetization dependence in the exchange-correlation functional are negligible for CF3Cl and CF3Br and small for CF3I. The noticeable effect of magnetization in the latter case is attributed to a near two-photon resonance with the excited state 1 E-3 (nonrelativistic notation). It is emphasized, however, that the effect of magnetization on beta for CF3I is negligible both in comparison to the total relativistic correction as well as to the effects of electron correlation. It is concluded that, in calculations of hyperpolarizabilities under nonresonant conditions, the magnetization dependence in the exchange-correlation functional may be ignored.

  • 8.
    Boström, Mathias
    et al.
    Royal Institute Technology, Sweden.
    Persson, Clas
    Royal Institute Technology, Sweden.
    Ninham, Barry W
    Australian National University, Australia.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Sernelius, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Resonance interaction induced by metal surfaces catalyzes atom-pair breakage2013In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 87, no 4Article in journal (Refereed)
    Abstract [en]

    We present the theory for retarded resonance interaction between two identical atoms at arbitrary positions near a metal surface. The dipole-dipole resonance interaction force that binds isotropically excited atom pairs together in free space may turn repulsive close to an ideal (totally reflecting) metal surface. On the other hand, close to an infinitely permeable surface it may turn more attractive. We illustrate numerically how the dipole-dipole resonance interaction between two oxygen atoms near a metal surface may provide a repulsive energy of the same order of magnitude as the ground-state binding energy of an oxygen molecule. As a complement we also present results from density-functional theory.

  • 9.
    Christodoulou, C.
    et al.
    Humboldt University, Germany .
    Giannakopoulos, A.
    University of Mons, Belgium .
    Nardi, M.V.
    Humboldt University, Germany .
    Ligorio, G.
    Humboldt University, Germany .
    Oehzelt, M.
    Humboldt University, Germany Helmholtz Zentrum Berlin Mat and Energie GmbH, Germany .
    Chen, L.
    University of Mons, Belgium .
    Pasquali, L.
    University of Modena and Reggio Emilia, Italy IOM CNR, Italy University of Johannesburg, South Africa .
    Timpel, M.
    Humboldt University, Germany .
    Giglia, A.
    IOM CNR, Italy .
    Nannarone, S.
    University of Modena and Reggio Emilia, Italy IOM CNR, Italy .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Parvez, K.
    Max Planck Institute Polymer Research, Germany .
    Muellen, K.
    Max Planck Institute Polymer Research, Germany .
    Beljonne, D.
    University of Mons, Belgium .
    Koch, N.
    Humboldt University, Germany Helmholtz Zentrum Berlin Mat and Energie GmbH, Germany .
    Tuning the Work Function of Graphene-on-Quartz with a High Weight Molecular Acceptor2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 9, p. 4784-4790Article in journal (Refereed)
    Abstract [en]

    Ultraviolet and X-ray photoelectron spectroscopies in combination with density functional theory (DFT) calculations were used to study the change in the work function (Phi) of graphene, supported by quartz, as induced by adsorption of hexaazatriphenylene-hexacarbonitrile (HATCN). Near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DFT modeling show that a molecular-density-dependent reorientation of HATCN from a planar to a vertically inclined adsorption geometry occurs upon increasing surface coverage. This, in conjunction with the orientation-dependent magnitude of the interface dipole, allows one to explain the evolution of graphene (Phi) from 4.5 eV up to 5.7 eV, rendering the molecularly modified graphene-on-quartz a highly suitable hole injection electrode.

  • 10.
    Coriani, Sonia
    et al.
    University of Aarhus.
    Christiansen, Ove
    University of Aarhus.
    Fransson, Thomas
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Coupled-cluster response theory for near-edge x-ray-absorption fine structure of atoms and molecules2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 85, no 2, p. 022507-Article in journal (Refereed)
    Abstract [en]

    Based on an asymmetric Lanczos-chain subspace algorithm, damped coupled cluster linear response functions have been implemented for the hierarchy of coupled cluster (CC) models including CC with single excitations (CCS), CC2, CC with single and double excitations (CCSD), and CCSD with noniterative triple corrected excitation energies CCSDR(3). This work is a first step toward the extension of these theoretical electronic structure methods of well-established high accuracy in UV-vis absorption spectroscopies to applications concerned with x-ray radiation. From the imaginary part of the linear response function, the near K-edge x-ray absorption spectra of neon, water, and carbon monoxide are determined and compared with experiment. Results at the CCSD level show relative peak intensities in good agreement with experiment with discrepancies in transition energies due to incomplete treatment of electronic relaxation and correlation that amount to 1-2 eV. With inclusion of triple excitations, errors in energetics are less than 0.9 eV and thereby capturing 90%, 95%, and 98% of the relaxation-correlation energies for C, O, and Ne, respectively.

  • 11.
    Coriani, Sonia
    et al.
    University of Trieste.
    Fransson, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Christiansen, Ove
    Aarhus University.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Asymmetric-Lanczos-Chain-Driven Implementation of Electronic Resonance Convergent Coupled-Cluster Linear Response Theory2012In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 8, no 5, p. 1616-1628Article in journal (Refereed)
    Abstract [en]

    We present an implementation of the damped coupled-cluster linear response function based on an asymmetric Lanczos chain algorithm for the hierarchy of coupled-cluster approximations CCS (coupled-cluster singles), CC2 (coupled. cluster singles and approximate doubles), and CCSD (coupled-cluster singles and doubles). Triple corrections to the excitation energies can be included via the CCSDR(3) (coupled-cluster singles and doubles with noniterative-triples-corrected excitation energies) approximation. The performance and some of the potentialities of the approach are investigated in calculations of the visible/ultraviolet absorption spectrum and the dispersion of the real polarizability in near-resonant regions of pyrimidine, the near-edge absorption fine structure (NEXAFS) of ammonia, and the direct determination of the C-6 dipole-dipole dispersion coefficient of the benzene dimer.

  • 12.
    Cronstrand, P
    et al.
    Royal Inst Technol, SE-10044 Stockholm, Sweden Ctr Chem, Dept Theoret Chem, SE-22100 Lund, Sweden Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Christiansen, O
    Royal Inst Technol, SE-10044 Stockholm, Sweden Ctr Chem, Dept Theoret Chem, SE-22100 Lund, Sweden Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Agren, H
    Royal Inst Technol, SE-10044 Stockholm, Sweden Ctr Chem, Dept Theoret Chem, SE-22100 Lund, Sweden Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Ab initio modeling of excited state absorption of polyenes2001In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 3, no 13, p. 2567-2575Article in journal (Refereed)
    Abstract [en]

    Vertical excitation energies and transition dipole moments between excited electronic states have been calculated for the trans-polyenes series C4H6-C12H14 in order to study the formation of excited state absorption spectra of these species. Quadratic response theory is applied in conjunction with the self-consistent field method and a hierarchical set of coupled-cluster methods. The convergence of the excited state absorption, with respect to wavefunction and treatment of electron correlation and also the length of the oligomer unit, is studied, revealing a considerable demand on the computational effort in order to predict the excited state spectra with precision. The organization of the excited states is found to change in character along the polyene series. The inflexion point for the vertical excitation energies between the one-photon allowed 1(1)B(u) and the two-photon 2(1)A(g) state is predicted to occur between hexatriene and octatetraene. Good agreement with experiment is obtained for butadiene and hexatriene for which the most accurate calculations have been carried out.

  • 13.
    Cronstrand, P
    et al.
    Royal Inst Technol, SE-10044 Stockholm, Sweden Univ Lund, Ctr Chem, Dept Theoret Chem, SE-22100 Lund, Sweden Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Christiansen, O
    Royal Inst Technol, SE-10044 Stockholm, Sweden Univ Lund, Ctr Chem, Dept Theoret Chem, SE-22100 Lund, Sweden Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Agren, H
    Royal Inst Technol, SE-10044 Stockholm, Sweden Univ Lund, Ctr Chem, Dept Theoret Chem, SE-22100 Lund, Sweden Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Theoretical calculations of excited state absorption2000In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 2, no 23, p. 5357-5363Article in journal (Refereed)
    Abstract [en]

    Excitation energies and transition dipole moments between excited electronic states have been calculated using various theoretical methods to investigate the ability to describe excited state absorption. Quadratic response theory is used in combination with self-consistent field, multi-configurational self-consistent field, and coupled-cluster electronic structure methods. The results of these different methods are compared. The set of molecules considered includes lithium hydride, carbon monoxide, formaldehyde, formamide, and sym-tetrazine. For some of the molecules results are also compared with the method of applying linear response theory to an excited state wavefunction separately optimized by means of the multi-configurational self-consistent field method.

  • 14.
    Cronstrand, P.
    et al.
    Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Luo, Y.
    Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Agren, H.
    Ågren, H., Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Ab initio calculations of three-photon absorption2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 375, no 1-2, p. 233-239Article in journal (Refereed)
    Abstract [en]

    We present large scale ab initio calculations of three-photon absorption of a series of dithienothiophene based charge transfer molecules using response theory within the random phase approximation. The structure-to-property relations obtained for the three-photon absorption cross-sections are discussed and compared with those for one- and two-photon absorption. © 2003 Published by Elsevier Science B.V.

  • 15.
    Cronstrand, P.
    et al.
    Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Luo, Y.
    Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Agren, H.
    Ågren, H., Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Few-states models for three-photon absorption2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, no 5, p. 2020-2029Article in journal (Refereed)
    Abstract [en]

    The validity of few-states models for several systems ranging from lithium hydride to a series of large p-conjugated systems was discussed. Various aspects of the models which include convergence, behavior, merits and shortcomings were studied. The role of various characteristics of the electronic structure such as symmetry and charge transfer was elaborated. Analysis suggests that few-states models can be useful for interpretation purposes when applied to three-photon absorption.

  • 16.
    Cukras, Janusz
    et al.
    University of Trieste, Italy.
    Coriani, Sonia
    University of Trieste, Italy.
    Decleva, Piero
    University of Trieste, Italy.
    Christiansen, Ove
    Aarhus University, Denmark.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Photoionization cross section by Stieltjes imaging applied to coupled cluster Lanczos pseudo-spectra2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 139, no 9Article in journal (Refereed)
    Abstract [en]

    A recently implemented asymmetric Lanczos algorithm for computing (complex) linear response functions within the coupled cluster singles (CCS), coupled cluster singles and iterative approximate doubles (CC2), and coupled cluster singles and doubles (CCSD) is coupled to a Stieltjes imaging technique in order to describe the photoionization cross section of atoms and molecules, in the spirit of a similar procedure recently proposed by Averbukh and co-workers within the Algebraic Diagrammatic Construction approach. Pilot results are reported for the atoms He, Ne, and Ar and for the molecules H2, H2O, NH3, HF, CO, and CO2.

  • 17.
    Cukras, Janusz
    et al.
    University of Trieste, Italy; University of Warsaw, Poland.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Rizzo, Antonio
    IPCF CNR, Italy.
    Rikken, Geert L. J. A.
    UPS, France; UPS, France.
    Coriani, Sonia
    University of Trieste, Italy; Aarhus University, Denmark.
    A complex-polarization-propagator protocol for magneto-chiral axial dichroism and birefringence dispersion2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 19, p. 13267-13279Article in journal (Refereed)
    Abstract [en]

    A computational protocol for magneto-chiral dichroism and magneto-chiral birefringence dispersion is presented within the framework of damped response theory, also known as complex polarization propagator theory, at the level of time-dependent Hartree-Fock and time-dependent density functional theory. Magneto-chiral dichroism and magneto-chiral birefringence spectra in the (resonant) frequency region below the first ionization threshold of R-methyloxirane and L-alanine are presented and compared with the corresponding results obtained for both the electronic circular dichroism and the magnetic circular dichroism. The additional information content yielded by the magneto-chiral phenomena, as well as their potential experimental detectability for the selected species, is discussed.

  • 18.
    Di Meo, Florent
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    Pedersen, Morten
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. University of Southern Denmark, Denmark.
    Rubio-Magnieto, Jenifer
    University of Mons UMONS, Belgium.
    Surin, Mathieu
    University of Mons UMONS, Belgium.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology. University of Mons UMONS, Belgium.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    DNA Electronic Circular Dichroism on the Inter-Base Pair Scale: An Experimental Theoretical Case Study of the AT Homo-Oligonucleotide2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 3, p. 355-359Article in journal (Refereed)
    Abstract [en]

    A successful elucidation of the near-ultraviolet electronic circular dichroism spectrum of a short double-stranded DNA is reported. Time-dependent density functional theory methods are shown to accurately predict spectra and assign bands on the microscopic base-pair scale, a finding that opens the field for using circular dichroism spectroscopy as a sensitive nanoscale probe of DNA to reveal its complex interactions with the environment.

  • 19.
    Ekström, Ulf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    X-ray absorption spectra from the resonantconvergent first-order polarization propagator approach2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 4, p. 042722-Article in journal (Refereed)
    Abstract [en]

    The one-photon absorption cross sections of molecular systems have been determined in the high-energy region from the imaginary part of the electric dipole polarizability tensor. In contrast to commonly adopted state-specific methodologies, the complex polarization propagator approach does not require explicit consideration of the excited states and it is open-ended towards multiphoton absorption. It is shown that the electronic relaxation in the core-hole state is well accounted for in the present approach with use of standard density-functional based electronic structure methods. Sample calculations are presented of the K-edge x-ray absorption spectra for H2O, CO, C4H4N, and C6H6.

  • 20.
    Ekström, Ulf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Carravetta, Vincenzo
    Istituto per i Processi Chimico-Fisici, Area della Ricerca del C.N.R., Pisa, Italy.
    Relativistic four-component static-exchange approximation for core-excitation processes in molecules2006In: Physical review A, ISSN 1050-2947, Vol. 73, no 2, p. 022501-Article in journal (Refereed)
    Abstract [en]

    A generalization of the static-exchange approximation for core-electron spectroscopies to the relativistic four-component realm is presented. The initial state is a Kramers restricted Hartree-Fock state and the final state is formed as the configuration-interaction single excited state, based on the average of configurations for (n–1) electrons in n near-degenerate core orbitals for the reference ionic state. It is demonstrated that the static-exchange Hamiltonian can be made real by considering a set of time-reversal symmetric electron excitation operators. The static-exchange Hamiltonian is constructed at a cost that parallels a single Fock matrix construction in a quaternion framework that fully exploits time-reversal and spatial symmetries for the D2h point group and subgroups. The K- and L-edge absorption spectra of H2S are used to illustrate the methodology. The calculations adopt the Dirac-Coulomb Hamiltonian, but the theory is open ended toward improvements in the electron-electron interaction operator. It is demonstrated that relativistic effects are substantial for the L-edge spectrum of sulfur, and substantial deviations from the statistical 2:1 spin-orbit splitting of the intensity distribution are found. The average ratio in the mixed region is 1.54 at the present level of theory.

  • 21.
    Ekström, Ulf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Carravetta, Vincenzo
    Istituto per i Processi Chimico-Fisici, Area della Ricerca del C.N.R., Pisa, Italy.
    Ågren, Hans
    Laboratory of Theoretical Chemistry, Royal Institute of Technology, Stockholm, Sweden.
    Polarization propagator for x-ray spectra2006In: Physical Review Letters, ISSN 1050-2947, Vol. 97, no 14, p. 143001-Article in journal (Refereed)
    Abstract [en]

    A polarization propagator for x-ray spectra is outlined and implemented in density functional theory. It rests on a formulation of a resonant-convergent first-order polarization propagator approach which makes it possible to directly calculate the x-ray absorption cross section at a particular frequency without explicitly addressing the excited states. The quality of the predicted x-ray spectrum relates only to the type of density functional applied without any separate treatment of dynamical relaxation effects.

  • 22.
    Ekström, Ulf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Ottosson, Henrik
    Department of Biochemistry and Organic Chemistry, Uppsala university, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Characterization of the chemisorption of methylsilane on a Au(1,1,1) surface from the silicon K- and L-edge spectra: a theoretical study using the four-component static exchange approximation2005In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, p. 13846-13850Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectra (NEXAFS) of methylsilane, isolated and chemisorbed to a Au(1,1,1) surface, are determined in the fully relativistic four-component static exchange approximation¯both the K- and the L-edge of silicon are addressed in this investigation. In the fully chemisorbed structure, three H(Si) atoms have been cleaved off when Si binds in the hollow site of Au forming three Si−Au bonds of normal length. As due to the tri-coordinated chemisorption, the onsets of the K- and L-edge NEXAFS absorption bands occur some 2.0 and 2.5 eV lower in energy, respectively. The spin−orbit splittings in the silicon 2p-shell are not significantly changed due to adsorption. A partly chemisorbed methylsilane with only one H(Si) bond cleaved was also studied, and it is shown that the polarization dependence in the surface spectra contains details that can be used experimentally to identify the surface coordination of silicon. The red-shifts in the XPS silicon 1s (2p) spectra upon surface binding are 0.95 (0.65) and 1.15 (0.83) eV for the mono- and tricoordinated system, respectively.

  • 23.
    Ekström, Ulf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Rizzo, Antonio
    Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche, Area della Ricerca, Pisa, Italy.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Four-component Hartree–Fock calculations of magnetic-field induced circular birefringence—Faraday effect—in noble gases and dihalogens2005In: The Journal of Chemical Physics, ISSN 1050-2947, Vol. 122, p. 074321-Article in journal (Refereed)
    Abstract [en]

    Theeffects of relativity on the magnetic-field induced circular birefringence, orFaraday effect, in He, Ne, Ar, Xe, Rn, F2, Cl2,Br2, and I2 have been determined at the four-component Hartree–Focklevel of theory. A measure of the birefringence is givenby the Verdet constant, which is a third-order molecular propertyand thus relates to quadratic response functions. A fully analyticalnonlinear polarization propagator approach is employed. The results are gaugeinvariant as a consequence of the spatial symmetries in themolecular systems. The calculations include electronic as well as vibrationalcontributions to the property. Comparison with experiment is made forHe, Ne, Ar, Xe, and Cl2, and, apart from neon,the theoretical values of the Verdet constant are within 10%of the experimental ones. The inclusion of nonrelativistically spin-forbidden excitationsin the propagator parametrization has significant effects on the dispersionin general, but such effects are in the general caselargely explained by the use of a resonant-divergent propagator theory.In the present work we do, however, observe noticeable relativisticcorrections to the Verdet constant in the off-resonant regions forsystems with light elements (F2 and Cl2), and nonrelativistic resultsfor the Verdet constant of Br2 are in error by25% in the low-frequency region. ©2005 American Institute of Physics.

  • 24.
    Elm, Jonas
    et al.
    University of Copenhagen, Denmark .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Bilde, Merete
    Aarhus University, Denmark .
    Mikkelsen, Kurt V.
    University of Copenhagen, Denmark .
    Computational study of the Rayleigh light scattering properties of atmospheric pre-nucleation clusters2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 22, p. 10883-10890Article in journal (Refereed)
    Abstract [en]

    The Rayleigh and hyper Rayleigh scattering properties of the binary (H2SO4)(H2O)(n) and ternary (H2SO4)(NH3)(H2O) n clusters are investigated using a quantum mechanical response theory approach. The molecular Rayleigh scattering intensities are expressed using the dipole polarizability alpha and hyperpolarizability beta tensors. Using density functional theory, we elucidate the effect of cluster morphology on the scattering properties using a combinatorial sampling approach. We find that the Rayleigh scattering intensity depends quadratically on the number of water molecules in the cluster and that a single ammonia molecule is able to induce a high anisotropy, which further increases the scattering intensity. The hyper Rayleigh scattering activities are found to be extremely low. This study presents the first attempt to map the scattering of atmospheric molecular clusters using a bottom-up approach.

  • 25.
    Elm, Jonas
    et al.
    University of Copenhagen, Denmark.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Mikkelsen, Kurt V.
    University of Copenhagen, Denmark.
    Rayleigh light scattering properties of atmospheric molecular clusters consisting of sulfuric acid and bases2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 24, p. 15701-15709Article in journal (Refereed)
    Abstract [en]

    The Rayleigh light scattering properties of (H2SO4)(a)(NH3)(b) and (H2SO4)(a)((CH3)(2)NH)(b) atmospheric molecular clusters have been investigated using a response theory approach. Using density functional theory the molecular structures and stepwise formation free energies of clusters with a and b up to 4 have been re-investigated. The Rayleigh scattering intensities are calculated from the dipole polarizability tensor a using the CAM-B3LYP functional by applying linear response methods. The intrinsic scattering properties of (H2SO4)(a)(NH3)(b) and (H2SO4)(a)((CH3)(2)NH)(b) indicate that amine containing clusters scatter light significantly more efficiently then their ammonia containing counterparts. Using the Atmospheric Cluster Dynamics Code (ACDC) the steady state cluster concentrations are estimated and the effective scattering is calculated. The effective scattering is shown to be highly dependent on the estimated concentrations and indicates that there exist competitive pathways, such as nucleation and coagulation, which influence the cluster distributions. The frequency dependence of the scattering is found to depend on the cluster composition and show increased responses when clusters contain more bases than acid molecules. Based on structures obtained using semi-empirical molecular dynamics simulations the Rayleigh scattering properties of clusters with up to 20 acid-base pairs are evaluated. This study represents the first step towards gaining a fundamental understanding of the scattering properties of small atmospheric clusters in the ambient atmosphere.

  • 26.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Coriani, Sonia
    University of Trieste, Italy .
    The magnetic circular dichroism spectrum of the C-60 fullerene2013In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 111, no 9-11, p. 1401-1404Article in journal (Refereed)
    Abstract [en]

    The magnetic circular dichroism spectrum of the C-60 fullerene has been determined with the use of Kohn-Sham density functional theory in conjunction with the CAM-B3LYP exchange-correlation functional. The experimental spectrum of Gasyna etal. [Chem. Phys. Lett. 183, 283 (1991)] covering the wavelength region above 200 nm is explained by the signal responses from the three lowest singlet states of T-1u symmetry.

  • 27.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Santoro, Fabrizio
    CNR, Italy.
    Improta, Roberto
    CNR, Italy.
    Coriani, Sonia
    University of Trieste, Italy; Aarhus University, Denmark.
    TD-DFT Investigation of the Magnetic Circular Dichroism Spectra of Some Purine and Pyrimidine Bases of Nucleic Acids2015In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 119, no 21, p. 5476-5489Article in journal (Refereed)
    Abstract [en]

    We present a computational study of the Magnetic circular dichroism (MCD) spectra in the 200-300 nm wavelength region of purine and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil,thymine, and cytosine, Using the B3LYP and CAM-B3LYP functionals. Solvent effects, are investigated within the polarizable continuum model and by inclusion of explicit water molecules. In, general; the computed spectra are found to be in good agreement with the experimental ones, aprt from some overall blue shifts. Both the pseudo-A term shape of the MCD spectra of the purines and the B term shape of the spectra of pyrimidine base are reproduced. Our calculations also correctly reproduce the reversed phase of the MCD bands in purine compared to,that of its derivatives present in nucleic acids. Solvent effects are sizable and system specific,but they do not in general alter the qualitative shape of the spectra. The bands are dominated the-bright pi -greater than pi* transitions; and our calculations in solution nicely reproduce theft energy differences, improving the estimates obtained in the gas phase. Shoulders are predicted for purine and uracil due to n -greater than pi* excitations, but they are too weak to be observed in the. experiment.

  • 28.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Resonant-convergent cubic response function in the random-phase approximation with application to two-photon absorption on neon in the ultraviolet-visible regionManuscript (preprint) (Other academic)
    Abstract [en]

    Damped cubic response functions are presented for exact-state and approximate-state methods eligible for quantum chemical computational applications. Proof of proper implementation is given, accompanied by a two-photon absorption example on neon in the ultraviolet-visible spectral region. The method accurately distinguish one- and two-photon resonances and exhibits spot-on agreement with other approaches.

  • 29.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Coriani, Sonia
    University of Trieste, Italy .
    Rizzo, Antonio
    UOS Pisa, Italy .
    Rikken, Geert L J A
    CNRS INSA UJF UPS, France .
    A density functional theory study of magneto-electric Jones birefringence of noble gases, furan homologues, and mono-substituted benzenes2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 139, no 19, p. 194311-Article in journal (Refereed)
    Abstract [en]

    We report on the results of a systematic ab initio study of the Jones birefringence of noble gases, of furan homologues, and of monosubstituted benzenes, in the gas phase, with the aim of analyzing the behavior and the trends within a list of systems of varying size and complexity, and of identifying candidates for a combined experimental/theoretical study of the effect. We resort here to analytic linear and nonlinear response functions in the framework of time-dependent density functional theory. A correlation is made between the observable (the Jones constant) and the atomic radius for noble gases, or the permanent electric dipole and a structure/chemical reactivity descriptor as the para Hammett constant for substituted benzenes.

  • 30.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Ågren, Hans
    KTH Royal Institute Technology, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden.
    A Polarization Propagator for Nonlinear X-ray Spectroscopies2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 11, p. 1991-1995Article in journal (Refereed)
    Abstract [en]

    A complex polarization propagator approach has been developed to third order and implemented in density functional theory (DFT), allowing for the direct calculation of nonlinear molecular properties in the X-ray wavelength regime without explicitly addressing the excited-state manifold. We demonstrate the utility of this propagator method for the modeling of coherent near-edge X-ray two-photon absorption using, as an example, DFT as the underlying electronic structure model. Results are compared with the corresponding near edge X-ray absorption fine structure spectra, illuminating the differences in the role of symmetry, localization, and correlation between the two spectroscopies. The ramifications of this new technique for nonlinear X-ray research are briefly discussed.

  • 31.
    Falklöf, Olle
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Durbeej, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Inter-Excited State Phosphorescence in the Four-Component Relativistic Kohn–Sham Approximation: A Case Study on Lumiflavin2015In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 119, no 49, p. 11911-11921Article in journal (Refereed)
    Abstract [en]

    Electronic transitions from one excited state to another excited state of different spin symmetry play important roles in many biochemical reactions. Although recent years have seen much progress in the elucidation of nonradiative (intersystem crossing) relaxation mechanisms for such transitions, there is presently a scarcity of data available to assess whether also radiative (phosphorescence) mechanisms are relevant for these processes. Here, we demonstrate that the well-established ability of quantum chemical methods to describe intersystem crossing events between excited states, can be supplemented by the ability to also describe inter-excited state phosphorescence. Specifically, performing four-component relativistic time-dependent density functional theory calculations, we obtain rate constants for the radiative transitions from the absorbing 1(πHπL*) singlet state of lumiflavin to the 3(πHπL*), 3(nN2πL*) and 3(πH–1πL*) triplet states, and subsequently compare these results with rate constants calculated for the corresponding nonradiative transitions. Thereby, it is found that the radiative rate constants for these particular transitions are typically two to five orders of magnitude smaller than the nonradiative ones.

  • 32.
    Fransson, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Burdakova, Daria
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 19, p. 13591-13603Article in journal (Other academic)
    Abstract [en]

    X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra—with spin-orbit effects well accounted for—also in cases when the experimental intensity ratio deviate from the statistical one of 1:2. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ~ 1 eV. This anomaly is observed also for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4−XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn–Sham density functional theory (DFT), and to a smaller extent with use of Hartree–Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems.

  • 33.
    Fransson, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Coriani, Sonia
    University of Trieste, Italy .
    Christiansen, Ove
    Aarhus University, Denmark .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Carbon X-ray absorption spectra of fluoroethenes and acetone: A study at the coupled cluster, density functional, and static-exchange levels of theory2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 12Article in journal (Refereed)
    Abstract [en]

    Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger pi-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to pi*-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate pi*-peak separations due to spectral compressions, a characteristic which is inherent to this method.

  • 34.
    Fransson, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Saue, Trond
    Laboratoire de Chimie et Physique Quantiques, UMR 5626 CNRS - Université Toulouse III-Paul Sabatier, Toulouse, France.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Four-component damped density functional response theory study of UV/vis absorption spectra and phosphorescence parameters of group 12 metal-substituted porphyrins2016In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 12, no 5, p. 2324-2334Article in journal (Refereed)
    Abstract [en]

    The influences of group 12 (Zn, Cd, Hg) metal-substitution on the valence spectra and phosphorescence parameters of porphyrins (P) have been investigated in a relativistic setting. In order to obtain valence spectra, this study reports the first application of the damped linear response function, or complex polarization propagator, in the four-component density functional theory framework [as formulated in J. Chem. Phys. 133, 064105 (2010)]. It is shown that the steep increase in the density of states as due to the inclusion of spin-orbit coupling yields only minor changes in overall computational costs involved with the solution of the set of linear response equations. Comparing single-frequency to multi-frequency spectral calculations, it is noted that the number of iterations in the iterative linear equation solver per frequency grid-point decreases monotonously from 30 to 0.74 as the number of frequency points goes from one to 19. The main heavy-atom effect on the UV/vis-absorption spectra is indirect and attributed to the change of point group symmetry due to metal-substitution, and it is noted that substitutions using heavier atoms yield small red-shifts of the intense Soret-band. Concerning phosphorescence parameters, the adoption of a four-component relativistic setting enables the calculation of such properties at a linear order of response theory, and any higher-order response functions does not need to be considered. For the substituted porphyrins, electronic coupling between the lowest triplet states is strong and results in theoretical estimates of lifetimes that are sensitive to the wave function and electron density parametrization. With this in mind, we report our best estimates of the phosphorescence lifetimes to be 460, 13.8, 11.2, and 0.00155 s for H2P, ZnP, CdP, and HgP, respectively, with the corresponding transition energies being equal to 1.46, 1.50, 1.38, and 0.89 eV.

  • 35.
    Fransson, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Zhovtobriukh, Iurii
    Fysikum, Stockholm University, Albanova, Stockholm, Sweden.
    Coriani, Sonia
    Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Trieste, Italy / Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark.
    Wikfeldt, Kjartan T.
    Fysikum, Stockholm University, Albanova, Stockholm, Sweden / Science Institute, University of Iceland, VR-III, Reykjavik, Iceland.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Pettersson, Lars G. M.
    Fysikum, Stockholm University, Albanova, Stockholm, Sweden.
    Requirements of first-principles calculations of X-ray absorption spectra of liquid water2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 1, p. 566-583Article in journal (Refereed)
    Abstract [en]

    A computational benchmark study on X-ray absorption spectra of water has been performed by means of transition-potential density functional theory (TP-DFT), damped time-dependent density functional theory (TDDFT), and damped coupled cluster (CC) linear response theory. For liquid water, using TDDFT with a tailored CAM-B3LYP functional and a polarizable embedding, we find that an embedding with over 2000 water molecules is required to fully converge spectral features for individual molecules, but a substantially smaller embedding can be used within averaging schemes. TP-DFT and TDDFT calculations on 100 MD structures demonstrate that TDDFT produces a spectrum with spectral features in good agreement with experiment, while it is more difficult to fully resolve the spectral features in the TP-DFT spectrum. Similar trends were also observed for calculations of bulk ice. In order to further establish the performance of these methods, small water clusters have been considered also at the CC2 and CCSD levels of theory. Issues regarding the basis set requirements for spectrum simulations of liquid water and the determination of gas-phase ionization potentials are also discussed.

  • 36.
    Glimsdal, Eirik
    et al.
    Norwegian University of Science & Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Norwegian University of Science & Technology.
    Excitation and Emission Properties of Platinum(II) Acetylides at High and Low Concentrations2009In: JOURNAL OF PHYSICAL CHEMISTRY A, ISSN 1089-5639, Vol. 113, no 42, p. 11242-11249Article in journal (Refereed)
    Abstract [en]

    Photophysical properties of platinum(II) acetylides in tetrahydrofuran (THF) solutions and incorporated in poly(methyl methacrylate) (PMMA) glasses have been studied over a large concentration range from 10 mu M to 50 mM. In general, the luminescence properties of the studied chromophores in the liquid state were also maintained in the solid state, except for shorter decay times of 50-90 mu s of the triplet state in the glass compared with 200-300 mu s in solution at low concentrations. The phosphorescence line shapes were found to be independent of both the chromophore concentration and the environment (THF and PMMA). The triplet state lifetimes did not change with concentration in the solid-state case, whereas, in solution, the decay becomes shorter at increasing concentration. The latter effect could be modeled with an additional linear quenching rate, k(q), in the range of (1 to 7) x 10(7) M-1 s(-1). Excitation spectra of the triplet state at high concentrations, in both solutions and solid glasses, showed additional excitation bands on the long wavelength side compared with the corresponding measurements at low concentrations. This indicates enhanced singlet-triplet coupling due to intermolecular electronic interactions that become important at concentrations of 0.1 to 1 mM and above.

  • 37.
    Henriksson, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Ekström, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    On the evaluation of quadratic response functions at the four-component Hartree-Fock level: Nonlinear polarization and two-photon absorption in bromo- and iodobenzen2006In: The Journal of Chemical Physics, ISSN 0021-9606, Vol. 124, no 21, p. 214311-Article in journal (Refereed)
    Abstract [en]

    The nonlinear polarization and two-photon absorption parameters have been determined for dibromo- and di-iodobenzene in their meta- and ortho-conformations and with relativistic effects accounted for to a varying degree. By exclusion of small component integrals in the calculations of the first-order hyperpolarizability, results within 1% of fully relativistic four-component Hartree-Fock values are obtained at a cost of 8.7 times the corresponding nonrelativistic calculations. It is shown that the nonlinear absorption in bromobenzene (and even more so in iodobenzene) is broad banded due to spin-orbit interactions among the excited states, and nonrelativistic and scalar relativistic calculations are not to be used in this case.

  • 38.
    Henriksson, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Jensen, Hans Jørgen Aa.
    Department of Chemistry, University of Southern Denmark, Odense M, Denmark.
    Two-photon absorption in the relativistic four-component Hartree-Fock approximation2005In: The Journal of Chemical Physics, ISSN 0021-9606, Vol. 122, no 11, p. 114106-Article in journal (Refereed)
    Abstract [en]

    A first implementation of the single residue of the quadratic response function in the four-component Hartree–Fock approximation is presented. The implementation is based on a Kramers paired molecular orbital basis and takes full advantage of time and spatial symmetry reductions in a quaternion formulation—in analogy with the previous work on the quadratic response function [J. Chem. Phys. 121, 6145 (2004)]. Sample calculations are given in terms of the monochromatic and coherent two-photon absorption cross sections in the noble gases. The relativistic two-photon selection rule J={0,±2} allows for nonrelativistically spin-forbidden transitions, and, even in neon, strong two-photon absorption is shown to occur for the X  1S02  3P2 transition. It is argued that relevant comparisons between nonrelativistic and relativistic calculations must be performed at the level of integrated absorption cross sections.

  • 39.
    Henriksson, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Nyrell, Susanna
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Theoretical design of optical switches using the spin transition phenomenon2006In: Computing Letters, ISSN 1574-0404, Vol. 2, no 4, p. 237-249Article in journal (Refereed)
    Abstract [en]

    The spin characteristics of octahedrically coordinated Fe(II) compounds are determined from first-principles quantum chemical calculations. Four novel Fe(II) spin transition materials are suggested for use in optical switching applications.

  • 40.
    Henriksson, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Saue, Trond
    CNRS et Université Louis Pasteur.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Quadratic response functions in the relativistic four-component Kohn-Sham approximation2008In: The Journal of Chemical Physics, ISSN 0021-9606, Vol. 128, no 2, p. 024105-Article in journal (Refereed)
    Abstract [en]

    A formulation and implementation of the quadratic response function in the adiabatic four-component Kohn-Sham approximation is presented. The noninteracting reference state is time-reversal symmetric and formed from Kramers pair spinors, and the energy density is gradient corrected. Example calculations are presented for the optical properties of disubstituted halobenzenes in their meta and ortho conformations. It is demonstrated that correlation and relativistic effects are not additive, and it is shown that relativity alone reduces the µ-response signal by 62% and 75% for meta- and ortho-bromobenzene, respectively, and enhances the same response by 17% and 21% for meta- and ortho-iodobenzene, respectively. Of the employed functionals, CAM-B3LYP shows the best performance and gives hyperpolarizabilities distinctly different from B3LYP

  • 41.
    Holmgaard List, Nanna
    et al.
    University of Southern Denmark, Denmark.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Saue, Trond
    University of Toulouse 3, France.
    Jorgen Aagaard Jensen, Hans
    University of Southern Denmark, Denmark.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Beyond the electric-dipole approximation: A formulation and implementation of molecular response theory for the description of absorption of electromagnetic field radiation2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, no 24, p. 244111-Article in journal (Refereed)
    Abstract [en]

    We present a formulation of molecular response theory for the description of a quantum mechanical molecular system in the presence of a weak, monochromatic, linearly polarized electromagnetic field without introducing truncated multipolar expansions. The presentation focuses on a description of linear absorption by adopting the energy-loss approach in combination with the complex polarization propagator formulation of response theory. Going beyond the electric-dipole approximation is essential whenever studying electric-dipole-forbidden transitions, and in general, non-dipolar effects become increasingly important when addressing spectroscopies involving higher-energy photons. These two aspects are examined by our study of the near K-edge X-ray absorption fine structure of the alkaline earth metals (Mg, Ca, Sr, Ba, and Ra) as well as the trans-polyenes. In following the series of alkaline earth metals, the sizes of non-dipolar effects are probed with respect to increasing photon energies and a detailed assessment of results is made in terms of studying the pertinent transition electron densities and in particular their spatial extension in comparison with the photon wavelength. Along the series of trans-polyenes, the sizes of non-dipolar effects are probed for X-ray spectroscopies on organic molecules with respect to the spatial extension of the chromophore.

  • 42.
    Huelsen, Michael
    et al.
    University of Cologne.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Dolg, Michael
    University of Cologne.
    Theoretical investigation of thermally and photochemically induced haptotropic rearrangements of chromium ligands on naphthalene systems2011In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 696, no 24, p. 3861-3866Article in journal (Refereed)
    Abstract [en]

    The description of chemical reactions by means of quantum mechanical methods is an important task and gets even more challenging if excited states have to be considered. This work focuses on the haptotropic rearrangements of chromium atoms bearing three coligands which migrate on a naphthalene-like system. The reactions are either thermally or photochemically controllable and thus the systems are candidates for molecular switches. We propose a detailed reaction scheme for the investigated system. Furthermore, we provide a detailed analysis of the important steps of the reaction cycle. In comparison to previous publications, the scope of this work also involves the quantum mechanical treatment of excited states in order to describe occurring photon absorption processes in a proper way. Linear response time-dependent density functional theory calculations were carried out to describe the molecules responses to the external electromagnetic perturbations. (C) 2011 Elsevier B.V. All rights reserved.

  • 43.
    Jansik, B.
    et al.
    Laboratory of Theoretical Chemistry, Department of Biotechnology, Royal Institute of Technology, Teknikringen 30, SE-10691 Stockholm, Sweden.
    Schimmelpfennig, B.
    Laboratory of Theoretical Chemistry, Department of Biotechnology, Royal Institute of Technology, Teknikringen 30, SE-10691 Stockholm, Sweden.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Macak, P.
    Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
    Agren, H.
    Ågren, H., Laboratory of Theoretical Chemistry, Department of Biotechnology, Royal Institute of Technology, Teknikringen 30, SE-10691 Stockholm, Sweden.
    Ohta, K.
    Photonics Research Institute, Natl. Inst. Adv. Indust. Sci./Tech., Kansai Center, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan.
    Relativistic effects on linear and non-linear polarizabilities of the furan homologues2003In: Journal of Molecular Structure: THEOCHEM, ISSN 0166-1280, Vol. 633, no 2-3, p. 237-246Article in journal (Refereed)
    Abstract [en]

    First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H 4, X = O, S, Se, Te, at three different levels of theory, time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these. © 2003 Elsevier B.V. All rights reserved.

  • 44. Jansik, B
    et al.
    Schimmelpfennig, B
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Mochizuki, Y
    Luo, Y
    Agren, H
    Size, order, and dimensional relations for silicon cluster polarizabilities2002In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 106, no 2, p. 395-399Article in journal (Refereed)
    Abstract [en]

    Response theory calculations in the random phase approximation are applied to linear polarizabilities and second hyperpolarizabilities of 1-, 2-, and 3-dimensional hydrogen-terminated silicon clusters. Successive enlargement of the clusters to embody on the order of 50 silicon atoms plus bond-saturating hydrogen atoms allows for extrapolation to bulk values of individual silicon atom contributions in the 1D and 3D cases. Modern effective core potentials are shown to provide excellent approximations to the all-electron values in all cases, errors for both polarizabilities and hyperpolarizabilities are on the order of 1%. The findings indicate considerable time savings in predictions of the electric polarizability properties of elements beyond the first row atoms.

  • 45.
    Jansson, Emil
    et al.
    Royal Institute of Technology.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Minaev, Boris
    Royal Institute of Technology.
    Ågren, Hans
    Royal Institute of Technology.
    Evaluation of low-scaling methods for calculation of phosphorescence parameters2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, p. 114106-1-114106-7Article in journal (Refereed)
    Abstract [en]

      

  • 46.
    Jiemchooroj, Auayporn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Ekström, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Near-edge X-ray absorption and natural circular dichroism spectra of L-alanine: a theoretical study based on the complex polarization propagator approach2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 16, p. 165104-Article in journal (Refereed)
    Abstract [en]

    The complex polarization propagator method [J. Chem. Phys. 123, 194103 (2005)] has been employed in conjunction with density functional theory and gauge-including atomic orbitals in order to determine the near-edge x-ray absorption and natural circular dichroism spectra of L-alanine in its neutral and zwitterionic forms. Results are presented for the K-edges of carbon, nitrogen, and oxygen. In contrast to traditional methods, the proposed approach enables a direct determination ofspectra at an arbitrary frequency instead of focusing on the rotatory strengths for individual electronic transitions. The propagator includes a complete set ofand allows for full core-hole relaxation. The theoretical spectrum at the nitrogen K-edge of the zwitterion compares well with the experimental spectrum. the nonredundant electron-transfer operators

  • 47.
    Jiemchooroj, Auayporn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Electronic circular dichroism spectra from the complex polarization propagator2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, no 13, p. 134102-Article in journal (Refereed)
    Abstract [en]

    The complex linear polarization propagator approach has been applied to the calculation of electronic circular dichroism spectra of 3R-chloro-1-butyne, 3R-methylcyclopentanone, 3S-methylcyclohexanone, 4R-1,1-dimethyl-[3]-(1,2)ferrocenophan-2-on, S-3,3,3,3-tetramethyl-1,1-spirobi[3H,2,1]-benzoxaselenole, and the fullerene C84. Using time-dependent Kohn-Sham density functional theory, it is shown that a direct and efficient evaluation of the circular dichroism spectrum can be achieved. The approach allows for the determination of the circular dichroism at an arbitrary wavelength thereby, in a common formulation and implementation, covering the visible, ultraviolet, and x-ray regions of the spectrum. In contrast to traditional methods, the entire manifold of excited states is taken into account in the calculation of the circular dichroism at a given wavelength

  • 48.
    Jiemchooroj, Auayporn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    X-ray absorption and natural circular dichroism spectra of C84: A theoretical study using the complex polarization propagator approach2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, no 23Article in journal (Refereed)
    Abstract [en]

    The x-ray absorption and circular dichroism K -edge spectra for the D2 -isomer of C84 have been determined using the complex polarization propagator method in conjunction with Kohn-Sham density functional theory. The circular dichroism spectrum is rich in details and, in comparison to the absorption spectrum, it provides a superior resolution of the electronic transitions below the ionization threshold. © 2008 American Institute of Physics.

  • 49.
    Jiemchooroj, Auayporn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Sernelius, Bo E.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Complex polarization propagator method for calculation of dispersion coefficients of extended π-conjugated systems: The C6 coefficients of polyacenes and C602005In: Journal of Chemical Physics, ISSN 0021-9606, Vol. 123, no 12, p. 124312-Article in journal (Refereed)
    Abstract [en]

    The frequency-dependent polarizabilities and the C6 dipole-dipole dispersion coefficients for the first members of the polyacenes namely benzene, naphthalene, anthracene, and naphthacene as well as the fullerene C60 have been calculated at the time-dependent Hartree-Fock level and the time-dependent density-functional theory level with the hybrid B3LYP exchange-correlation functional. The dynamic polarizabilities at imaginary frequencies are obtained with use of the complex linear polarization propagator method and the C6 coefficients are subsequently determined from the Casimir-Polder relation. We report the first ab initio calculations of the C6 coefficients for the molecules under consideration, and our recommended value for the dispersion coefficient of the fullerene is 101.0  a.u.

  • 50.
    Jiemchooroj, Auayporn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Sernelius, Bo. E.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Electric dipole polarizabilities and C6 dipole-dipole dispersion coefficients for sodium clusters and C602006In: Journal of Chemical Physics, ISSN 0021-9606, Vol. 125, no 12, p. 124306-Article in journal (Refereed)
    Abstract [en]

    The frequency-dependent polarizabilities of closed-shell sodium clusters containing up to 20 atoms have been calculated using the linear complex polarization propagator approach in conjunction with Hartree-Fock and Kohn-Sham density functional theories. In combination with polarizabilities for C60 from a previous work [J. Chem. Phys. 123, 124312 (2005)], the C6 dipole-dipole dispersion coefficients for the metal-cluster-to-cluster and cluster-to-buckminster-fullerene interactions are obtained via the Casimir-Polder relation [Phys. Rev. 73, 360 (1948)]. The B3PW91 results for the polarizability of the sodium dimer and tetramer are benchmarked against coupled cluster calculations. The error bars of the reported theoretical results for the C6 coefficients are estimated to be 5%, and the results are well within the error bars of the experiment.

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