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  • 1. Andersson, P H
    et al.
    Klintenberg, Mattias
    Henningsson, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sandell, A
    Siegbahn, H
    Katsnelson, M I
    Sanyal, Biplab
    Wessely, O
    Eriksson, O
    Initial and final state effects in x-ray absorption spectra of transition metal oxidesArticle in journal (Refereed)
  • 2.
    Andersson, P. H.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Klintenberg, Mattias
    Henningsson, A.
    Siegbahn, H.
    Eriksson, Olle
    Charge transfer effets in x-ray absorption spectroscopy of transition metal oxidesIn: Phys. Rev. Lett.Article in journal (Refereed)
  • 3.
    Andersson, P H
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Klintenberg, Mattias
    Henningsson, A
    Siegbahn, H
    Eriksson, Olle
    Electronic structure and x-ray absorption spectroscopy of TiO2 and LiTi2O4Manuscript (Other academic)
  • 4.
    Bläckberg, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Fay, A.
    Jõgi, Indrek
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Biegalski, S.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Elmgren, K.
    Fritioff, T.
    Johansson, A.
    Martensson, L.
    Nielsen, F.
    Ringbom, A.
    Rooth, Mårten
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 656, no 1, p. 84-91Article in journal (Refereed)
    Abstract [en]

    In this work Al(2)O(3) and SiO(2) coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al(2)O(3) coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.

  • 5.
    Bläckberg, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Fritioff, T.
    Martensson, L.
    Nielsen, F.
    Ringbom, A.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Memory effect, resolution, and efficiency measurements of an Al2O3 coated plastic scintillator used for radioxenon detection2013In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 714, p. 128-135Article in journal (Refereed)
    Abstract [en]

    A cylindrical plastic scintillator cell, used for radioxenon monitoring within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, has been coated with 425 nm Al2O3 using low temperature Atomic Layer Deposition, and its performance has been evaluated. The motivation is to reduce the memory effect caused by radioxenon diffusing into the plastic scintillator material during measurements, resulting in an elevated detection limit. Measurements with the coated detector show both energy resolution and efficiency comparable to uncoated detectors, and a memory effect reduction of a factor of 1000. Provided that the quality of the detector is maintained for a longer period of time, Al2O3 coatings are believed to be a viable solution to the memory effect problem in question.

  • 6.
    Bläckberg, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Fritioff, Tomas
    Mårtensson, Lars
    Nielsen, Fredrik
    Ringbom, Anders
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Measurements of memory effect and resolution for an Al2O3 coated plastic scintillator used for radioxenon detectionManuscript (preprint) (Other academic)
    Abstract [en]

    A cylindrical plastic scintillator cell, used for radioxenon monitoring within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, has been coated with 425 nm Al2O3 using low temperature Atomic Layer Deposition, and its performance has been evaluated. The motivation is to reduce the memory effect caused by radioxenon diffusing into the plastic scintillator material during measurements, resulting in an elevated detection limit. Measurements of the coated detector show a resolution comparable to uncoated detectors, and a memory effect reduction of a factor of 1000. If these results are reproducible, and the quality of the detector is maintained for a longer period of time, the Al2O3 coating method is believed to be viable solution to the memory effect problem in question.

  • 7.
    Bläckberg, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ringbom, Anders
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Effects of surface coatings on the light collection in plastic scintillators used for radioxenon detection2012In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T150, p. 014007-Article in journal (Refereed)
    Abstract [en]

    Atomic Layer Deposition coatings are under investigation to reduce diffusion of radioxenon into plastic scintillators. This paper investigates the impact of such surface coating on the light collection efficiency in a cylindrical geometry. A high and uniform light collection efficiency is important to preserve detector resolution. Monte Carlo simulations and measurements have been performed to study the influence of coating thickness, refractive index, and surface quality. It was found important to achieve a smooth coating, and a good optical match between the refractive indices of the coating and the plastic scintillator. Taking these considerations into account, the detector under study could be coated without significant degradation of its resolution.

  • 8.
    Bläckberg, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Metsanurk, Erki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Tamm, Artur
    University of Tartu, Estonia.
    Aabloo, Alvo
    University of Tartu, Estonia.
    Mattias, Klintenberg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Molecular dynamics study of Xenon on an amorphous Al2O3 surface2014In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 759, p. 10-15Article in journal (Refereed)
  • 9.
    Bläckberg, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ringbom, A.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Klintenberg, Mattias K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Assisted self-healing in ripped graphene2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 19, p. 195434-Article in journal (Refereed)
    Abstract [en]

    A monolayer of sp(2)-bonded carbon (graphene) is a material with great technological promise because of, for example, its transport, electrical, optical, and mechanical properties. In this work noble gas diffusion through ripped graphene sheets is explored. The motivation is improved detection systems used worldwide to verify compliance of the Comprehensive Nuclear-Test-Ban Treaty. It is demonstrated that even ripped graphene sheets and/or nonoverlapping graphene flakes inhibit noble gas diffusion. The latter has been shown for He and Xe where an infinitely long rip was constructed to have Stone-Wales edges. It is also shown that the ripped graphene layer self-heal in an alternating pentagon, hexagon, heptagon (5-6-7) and 7-6-5 pattern perpendicular to the rip. Moreover, the noble gas (He and Xe) assists in the healing process of wider rips.

  • 10.
    Brandell, D
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Klintenberg, Mattias
    Aabloo, A
    Thomas, JO
    Calculation of the optical absorption spectrum of ErCl3 in poly(ethylene oxide) (PEO)2000In: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, ISSN 0020-7608, Vol. 80, no 4-5, p. 799-806Article in journal (Refereed)
    Abstract [en]

    The optical absorption spectrum for the rare-earth ion Er3+ in a, amorphous polymer host poly(ethylene oxide) (PEO) has been calculated. A modified Judd-Ofelt theory has been exploited to calculate the oscillator strengths for the electric-dipole transiti

  • 11.
    Butorin, Sergei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kvashnina, K. O.
    European Synchrotron, Grenoble, France; HZDR, Inst Resource Dresden, Germany.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kavcic, M.
    Joief Stefan Inst, Ljubljana, Slovenia.
    Zitnik, Mihael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Joief Stefan Inst, Ljubljana, Slovenia; Univ Ljubljana, Fac Math & Phys, Ljubljana, Slovenia.
    Bucar, K.
    Joief Stefan Inst, Ljubljana, Slovenia.
    Gougeon, P.
    Univ Rennes 1, INSA Rennes, Inst Sci Chim Rennes, Rennes, France.
    Gall, P.
    Univ Rennes 1, INSA Rennes, Inst Sci Chim Rennes, Rennes, France.
    Candolfi, C.
    Univ Lorraine, CNRS, UMR 7198, Inst Jean Lamour, Nancy, France; Univ Lorraine, UMR 7198 CNRS, Inst Jean Lamour, Nancy, France.
    Lenoir, B.
    Univ Lorraine, CNRS, UMR 7198, Inst Jean Lamour, Nancy, France; Univ Lorraine, UMR 7198 CNRS, Inst Jean Lamour, Nancy, France.
    Effect of Ag Doping on Electronic Structure of Cluster Compounds AgxMo9Se11 (x = 3.4, 3.9)2018In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 1, no 8, p. 4032-4039Article in journal (Refereed)
    Abstract [en]

    The electronic structure of AgxMo9Se11 as a potential material for thermoelectric applications was studied using high-energy-resolution fluorescence-detection X-ray absorption spectroscopy (HERFD-XAS) and the resonant inelastic X-ray scattering (RIXS) technique. The experiments were supported by first-principle calculations using density functional theory (DFT). The analysis of obtained spectra indicate the presence of subvalent (less than 1+) Ag in AgxMo9Se11. The advanced HERFD-XAS measurements allowed us to resolve the contribution of the electronic states at the Fermi level of AgxMo9Se11 and to monitor its dependence on the x value. A comparison of the experimental data with the results of the DFT calculations suggests the importance of the Ag2-type sites with the shortest Ag–Se distance for affecting the properties of AgxMo9Se11.

  • 12.
    Béland, Laurent Karim
    et al.
    MIT, MIT CNRS Joint Lab, Multiscale Mat Sci Energy & Environm.;Oak Ridge Natl Lab, Mat Sci & Technol Div. .
    Tamm, Artur
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Tartu, Inst Technol, Intelligent Mat & Syst Lab..
    Mu, Sai
    Oak Ridge Natl Lab, Mat Sci & Technol Div..
    Samolyuk, German D.
    Oak Ridge Natl Lab, Mat Sci & Technol Div..
    Osetsky, Yuri N.
    Oak Ridge Natl Lab, Mat Sci & Technol Div..
    Aabloo, Alvo
    Univ Tartu, Inst Technol, Intelligent Mat & Syst Lab..
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Caro, Alfredo
    Los Alamos Natl Lab, Mat Sci & Technol Div..
    Stoller, Roger E.
    Oak Ridge Natl Lab, Mat Sci & Technol Div..
    Accurate classical short-range forces for the study of collision cascades in Fe-Ni-Cr2017In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 219, p. 11-19Article in journal (Refereed)
    Abstract [en]

    The predictive power of a classical molecular dynamics simulation is largely determined by the physical validity of its underlying empirical potential. In the case of high-energy collision cascades, it was recently shown that correctly modeling interactions at short distances is necessary to accurately predict primary damage production. An ab initio based framework is introduced for modifying an existing embedded atom method FeNiCr potential to handle these short-range interactions. Density functional theory is used to calculate the energetics of two atoms approaching each other, embedded in the alloy, and to calculate the equation of state of the alloy as it is compressed. The pairwise terms and the embedding terms of the potential are modified in accordance with the ab initio results. Using this reparametrized potential, collision cascades are performed in Ni50Fe50, Ni80Cr20 and Ni33Fe33Cr33. The simulations reveal that alloying Ni and NiCr to Fe reduces primary damage production, in agreement with some previous calculations. Alloying Ni and NiFe to Cr does not reduce primary damage production, in contradiction with previous calculations.

  • 13.
    Caleman, Carl
    et al.
    Physik Department E17, Technische Universität München.
    Ortiz, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Marklund, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Bultmark, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Gabrysch, Markus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Parak, F. G.
    Hajdu, Janos
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Timneanu, Nicusor
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Radiation damage in biological material: electronic properties and electron impact ionization in urea2009In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 85, no 1, p. 18005-Article in journal (Refereed)
    Abstract [en]

    Radiation damage is an unavoidable process when performing structural investigations of biological macromolecules with X-rays. In crystallography this process can be limited through damage distribution in a crystal, while for single molecular imaging it can be outrun by employing short intense pulses. Secondary electron generation is crucial during damage formation and we present a study of urea, as model for biomaterial. From first principles we calculate the band structure and energy loss function, and subsequently the inelastic electron cross-section in urea. Using Molecular Dynamics simulations, we quantify the damage and study the magnitude and spatial extent of the electron cloud coming from an incident electron, as well as the dependence with initial energy.

  • 14.
    Costa, Marcio
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Venezuela, P.
    Instituto de Física, Universidade Federal Fluminense, Rio de Janeiro, Brasilien.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Large magnetic anisotropy of Fe2P investigated via ab initio density functional theory calculations2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 8, p. 085125-Article in journal (Refereed)
    Abstract [en]

    We present an investigation of the large magnetic anisotropy of Fe2P, based on ab initio density functional theory calculations, with a full-potential linear muffin-tin orbital basis. We obtain a uniaxial magnetic anisotropy energy (MAE) of 664 mu eV/f.u., which is in decent agreement with experimental observations. Based on a band structure analysis the microscopic origin of the large magnetic anisotropy is explained. We also show that by straining the crystal structure, the MAE can be enhanced further.

  • 15.
    de Almeida, J. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Kim, D. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ortiz, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    On the dynamical stability and metallic behavior of YH3 under pressure2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 25, p. 251913-Article in journal (Refereed)
    Abstract [en]

    Wereport on the behavior of structural and electronic properties ofyttrium trihydride under pressure using first principles calculations. We showthat YH3 undergoes a structural transformation and its high pressurephase is dynamically stable under pressure since the peak atthe imaginary frequencies of the phonon density of states, whichaccount for the structural instability disappears at high pressure. Additionally,our GW calculations indicate a metallization of the high pressurecubic phase of YH3.

  • 16. Derenzo, S. E.
    et al.
    Bourret-Courchesne, E.
    Weber, M. J.
    Klintenberg, Mattias
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV.
    Scintillation studies of CdS(In): effects of various semiconductor doping strategies2005In: Nuclear Instruments and Methods in Physics Research Section A, ISSN 0168-9002, Vol. 537, no 1-2, p. 261-Article in journal (Refereed)
    Abstract [en]

    We present room-temperature photoluminescence and pulsed X-ray measurements of powder samples of CdS(In) codoped with three hole traps (Te, Ag, and Na). Te is an isoelectronic hole trap and Ag, and Na are acceptor hole traps. The emission of CdS(In) excited at 430 nm is centered at approximate to 520 nm (near the band edge) with approximate to 20 nm FWHM. The emissions from CdS(Te) and the three codoped samples are shifted to longer wavelengths and are characterized by broad emission bands peaking near 630 nm. Whereas the decay of the CdS(Te) emission is nonexponential with times > 10 its, the decay of CdS(In, Te) is 3.3 ns and exponential over three decades. The decay of the acceptor-doped samples CdS(In,Ag) and CdS(In, Na) are also fast, 2.5 and 2.8 ns, respectively. These results show the potential for developing fast inorganic scintillators based on direct-gap semiconductors that can be codoped to provide fast radiative recombination. Additional work is needed to increase the luminosity.

  • 17. Fiori, G.
    et al.
    Lebegue, S.
    Betti, A.
    Michetti, P.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Iannaccone, G.
    Simulation of hydrogenated graphene field-effect transistors through a multiscale approach2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 15, p. 153404-Article in journal (Refereed)
    Abstract [en]

    In this work, we present a performance analysis of field-effect transistors (FETs) based on recently fabricated 100% hydrogenated graphene (the so-called graphane) and theoretically predicted semihydrogenated graphene (i.e., graphone). The approach is based on accurate calculations of the energy bands by means of GW approximation, subsequently fitted with a three-nearest neighbor sp(3) tight-binding Hamiltonian, and finally used to compute ballistic transport in transistors based on functionalized graphene. Due to the large energy gap, the proposed devices have many of the advantages provided by one-dimensional graphene nanoribbon FETs, such as large I-on and I-on/I-off ratios, reduced band-to-band tunneling, without the corresponding disadvantages in terms of prohibitive lithography and patterning requirements for circuit integration.

  • 18.
    Henningsson, A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sandell, A
    Siegbahn, H
    Andersson, P H
    Katsnelson, M I
    Sanyal, Biplab
    Klintenberg, Mattias
    Wessely, O
    Eriksson, O
    Electronic structure and x-ray absorption spectroscopy of TiO2 and Li0.5TiO2Manuscript (Other academic)
  • 19.
    Klintenberg, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Possible high-temperature superconductors predicted from electronic structure and data-filtering algorithms2013In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 67, p. 282-286Article in journal (Refereed)
    Abstract [en]

    We report here the completion of the electronic structure of the majority of the known stoichiometric inorganic compounds, as listed in the Inorganic Crystal Structure Data-base (ICSD). We make a detailed comparison of the electronic structure, crystal geometry and chemical bonding of cuprate high temperature superconductors, with the calculated over 60,000 electronic structures. Based on compelling similarities of the electronic structures in the normal state and a data-filtering technique, we propose that high temperature superconductivity is possible for electron-or hole-doping in a much larger group of materials than previously considered. The identified materials are composed of over 100 layered compounds, most which hitherto are untested with respect to their super conducting properties. Of particular interest are the following materials; Ca2CuBr2O2, K2CoF4, and Sr2MoO4, which are discussed in detail.

  • 20.
    Klintenberg, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Lebegue, S.
    Katsnelson, M. I.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Theoretical analysis of the chemical bonding and electronic structure of graphene interacting with Group IA and Group VIIA elements2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 8, p. 085433-Article in journal (Refereed)
    Abstract [en]

    We propose a different class of materials, which can be viewed as graphene derivatives involving Group IA or Group VIIA elements, forming what we refer to as graphXene. We show that in several cases, large band gaps can be found to open up whereas in other cases, a semimetallic behavior is found. Formation energies indicate that under ambient conditions, sp(3) and mixed sp(2)/sp(3) systems will form. The results presented allow us to propose that by careful tuning of the relative concentration of the adsorbed atoms, it should be possible to tune the band gap of graphXene to take any value between 0 and 6.4 eV.

  • 21.
    Klintenberg, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Lebegue, S
    Ortiz, C
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Fransson, J
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Evolving properties of two-dimensional materials: from graphene to graphite2009In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 21, no 33, p. 335502-Article in journal (Refereed)
    Abstract [en]

    We have studied theoretically, using density functional theory, several material properties when going from one C layer in graphene to two and three graphene layers and on to graphite. The properties we have focused on are the elastic constants, electronic structure (energy bands and density of states), and the dielectric properties. For any of the properties we have investigated the modification due to an increase in the number of graphene layers is within a few per cent. Our results are in agreement with the analysis presented recently by Kopelevich and Esquinazi (unpublished).

  • 22. Lebegue, S.
    et al.
    Bjorkman, T.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nieminen, R. M.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Two-Dimensional Materials from Data Filtering and Ab Initio Calculations2013In: Physical Review X, ISSN 2160-3308, E-ISSN 2160-3308, Vol. 3, no 3, p. 031002-Article in journal (Refereed)
    Abstract [en]

    Progress in materials science depends on the ability to discover new materials and to obtain and understand their properties. This has recently become particularly apparent for compounds with reduced dimensionality, which often display unexpected physical and chemical properties, making them very attractive for applications in electronics, graphene being so far the most noteworthy example. Here, we report some previously unknown two-dimensional materials and their electronic structure by data mining among crystal structures listed in the International Crystallographic Structural Database, combined with density-functional-theory calculations. As a result, we propose to explore the synthesis of a large group of two-dimensional materials, with properties suggestive of applications in nanoscale devices, and anticipate further studies of electronic and magnetic phenomena in low-dimensional systems.

  • 23. Lebegue, S
    et al.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Katsnelson, M.I.
    Accurate electronic band gap of pure and functionalized graphane from GW calculations2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 24, p. 245117-Article in journal (Refereed)
    Abstract [en]

    Using the GW approximation, we study the electronic structure of the recently synthesized hydrogenated graphene, named graphane. For both conformations, the minimum band gap is found to be direct at the Gamma point, and it has a value of 5.4 eV in the stable chair conformation, where H atoms attach C atoms alternatively on opposite sides of the two-dimensional carbon network. In the metastable boat conformation the energy gap is 4.9 eV. Then, using a supercell approach, the electronic structure of graphane was modified by introducing either a hydroxyl group or an H vacancy. In this last case, an impurity state appears at about 2 eV above the valence-band maximum.

  • 24.
    Lewin, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Råsander, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Design of the Lattice Parameter of Embedded Nanoparticles2010In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 496, no 1-3, p. 95-99Article in journal (Refereed)
    Abstract [en]

    It is found that the bonding of nanoparticles in nancomposites can be influenced by interactions with a surrounding matrix phase. A model involving charge transfer between phases is presented, and supported by DFT-simulations. The model explains observations in nanocomposite nc-TiCx/a-C of additional interface states and lattice expansion of TiCx. It is suggested that this approach can be extended to other types of nanocomposites, and that it opens for new possibilities in materials design.

  • 25.
    Lindström, A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Mirbt, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    High resistivity in undoped CdTe: carrier compensation of Te antisites and Cd vacancies2016In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 3, article id 035101Article in journal (Refereed)
    Abstract [en]

    In this paper, we focus on the high resistivity of intentionally undoped CdTe, where the most prevalent defects are Cd vacancies and Te antisites. Our calculated formation energies lead to the conclusion that the Fermi energy of undoped CdTe is at midgap due to carrier compensation of Te antisites and Cd vacancies, which explains the experimentally observed high resistivity. We use density functional theory with the hybrid functional of Heyd, Scuseria and Ernzerhof (HSE06) and show that the proper description of the native defects in general fails using the local density approximation (LDA) instead of HSE06. We conclude that LDA is insufficient to understand the high resistivity of undoped CdTe. We calculate the neutral and double acceptor state of the Te antisite to be intrinsic DX-centers.

  • 26.
    Lindström, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mirbt, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Cl-doping of Te-rich CdTe: Complex formation, self-compensation and self-purification from first principles2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 8, article id 087101Article in journal (Refereed)
    Abstract [en]

    The coexistence in Te-rich CdTe of substitutional Cl-dopants, Cl-Te, which act as donors, and Cd vacancies, V-Cd(-1), which act as electron traps, was studied from first principles utilising the HSE06 hybrid functional. We find ClTe to preferably bind to V-Cd(-1) and to form an acceptor complex, (Cl-Te-V-Cd)(-1).The complex has a (0,-1) charge transfer level close to the valence band and shows no trap state (deep level) in the band gap. During the complex formation, the defect state of V-Cd-(1) is annihilated and leaves the Cl-doped CdTe bandgap without any trap states (self-purification). We calculate Cl-doped CdTe to be semi-insulating with a Fermi energy close to midgap. We calculate the formation energy of the complex to be sufficiently low to allow for spontanous defect formation upon Cl-doping (self-compensation). In addition, we quantitatively analyse the geometries, DOS, binding energies and formation energies of the (Cl-Te-V-Cd) complexes.

  • 27.
    Metsanurk, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Tamm, A.
    Caro, A.
    Aabloo, A.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    First-principles study of point defects at a semicoherent interface2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 7567-Article in journal (Refereed)
    Abstract [en]

    Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. We show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. We give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials.

  • 28.
    Metsanurk, Erki
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sampling-dependent systematic errors in effective harmonic models2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 18, article id 184304Article in journal (Refereed)
    Abstract [en]

    Effective harmonic methods allow for calculating temperature-dependent phonon frequencies by incorporating the anharmonic contributions into an effective harmonic Hamiltonian. The systematic errors arising from such an approximation are explained theoretically and quantified by density-functional-theory-based numerical simulations. Two techniques with different approaches for sampling the finite-temperature phase space in order to generate the force-displacement data are compared. It is shown that the error in free energy obtained by using either can exceed that obtained from 0 K harmonic lattice dynamics analysis, which neglects the anharmonic effects.

  • 29.
    Metsanurk, Erki
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Tamm, Artur
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Tartu, Inst Technol, Intelligent Mat & Syst Lab, EE-50411 Tartu, Estonia.
    Aabloo, A.
    Univ Tartu, Inst Technol, Intelligent Mat & Syst Lab, EE-50411 Tartu, Estonia.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Caro, A.
    Los Alamos Natl Lab, Los Alamos, NM 87545 USA.
    Vacancies at the Cu-Nb semicoherent interface2017In: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 25, no 2, article id 025012Article in journal (Refereed)
    Abstract [en]

    We present the 0 K structures and formation energies for vacancy clusters of up to four vacancies and migration barriers for a single vacancy at a semicoherent Kurdjumov-Sachs Cu-Nb interface using ab initio calculations. Two main results emerge from this study, first that the predicted vacancy structure is compact, differing notoriously with predictions based on available empirical potentials, and second that vacancy clusters containing up to four vacancies have a smaller formation energy than monovacancy in bulk. Additionally, the binding energies show that the vacancy clusters are energetically stable for clusters having up to four vacancies. Nudged elastic band calculations of migration barriers show that the migration of a vacancy from one misfit dislocation intersection to another is highly improbable due to the high barriers. These findings suggest that at nonzero temperatures the interface will be preloaded with vacancy clusters with a relatively large capture radius for interstitials in the interface plane, implying that the semicoherent Cu-Nb interface could be a highly effective sink for point defects that form due to irradiation.

  • 30.
    Ortiz, Carlos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Data mining and accelerated electronic structure theory as a tool in the search for new functional materials2009In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 44, no 4, p. 1042-1049Article in journal (Refereed)
    Abstract [en]

    A highly accelerated electronic structure implementation and data mining algorithms have been combined with structural data from the inorganic crystal structure database to generate materials properties for about 22,000 inorganic compounds. It is shown how data mining algorithms employed on the database can identify new functional materials with desired materials properties, resulting in a prediction of 136 novel materials with potential for use as detector materials for ionizing radiation. The methodology behind the automatized ab initio approach is presented, results are tabulated and a version of the complete database is made available at the internet web site

  • 31.
    Phuyal, Dibya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Jain, Sagar Motilal
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Swansea Univ, Coll Engn, SPECIFIC, Bay Campus,Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Malin B
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Kullgren, Jolla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Kvashnina, Kristina O.
    ESRF, Rossendorf Beamline, CS40220, F-38043 Grenoble 9, France;HZDR, Inst Resource Ecol, POB 510119, D-01314 Dresden, Germany.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Johansson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy2018In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 20, p. 9498-9505Article in journal (Refereed)
    Abstract [en]

    Bismuth halide compounds as a non-toxic alternative are increasingly investigated because of their potential in optoelectronic devices and their rich structural chemistry. Hard X-ray spectroscopy was applied to the ternary bismuth halide Cs3Bi2I9 and its related precursors BiI3 and CsI to understand its electronic structure at an atomic level. We specifically investigated the core levels and valence band using X-ray photoemission spectroscopy (PES), high-resolution X-ray absorption (HERFD-XAS), and resonant inelastic X-ray scattering (RIXS) to get insight into the chemistry and the band edge properties of the two bismuth compounds. Using these element specific X-ray techniques, our experimental electronic structures show that the primary differences between the two bismuth samples are the position of the iodine states in the valence and conduction bands and the degree of hybridization with bismuth lone pair (6s(2)) states. The crystal structure of the two layered quasi-perovskite compounds plays a minor role in modifying the overall electronic structure, with variations in bismuth lone pair states and iodine band edge states. Density Functional Theory (DFT) calculations are used to compare with experimental data. The results demonstrate the effectiveness of hard X-ray spectroscopies to identify element specific bulk electronic structures and their use in optoelectronic devices.

  • 32. Råsander, Mikael
    et al.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Carbon Release by Selective Alloying of Transition Metal Carbides2011In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 35, p. 355401-+Article in journal (Refereed)
    Abstract [en]

    We have performed first principles density functional theory calculations on TiC alloyed on the Ti sublattice with 3d transition metals ranging from Sc to Zn. The theory is accompanied by experimental investigations, both as regards materials synthesis as well as characterization. Our results show that by dissolving a metal with a weak ability to form carbides, the stability of the alloy is lowered and a driving force for the release of carbon from the carbide is created. During thin film growth of a metal carbide this effect will favour the formation of a nanocomposite with carbide grains in a carbon matrix. The choice of alloying element as well as its concentration will affect the relative amount of carbon in the carbide and in the carbon matrix. This can be used to design the structures of nanocomposites and their physical and chemical properties. One example of applications is as low-friction coatings. Of the materials studied, we suggest the late 3d transition metals as the most promising elements for this phenomenon, at least when alloying with TiC.

  • 33.
    Shepidchenko, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mirbt, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Håkansson, Ane
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Tailoring of defect levels by deformations: Te-antisite in CdTe2013In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 41, p. 415801-Article in journal (Refereed)
    Abstract [en]

    The properties of the Te-antisite defect in the neutral state in CdTe were examined using ab initio calculations. The influence of three types of deformations (1D, 2D and 3D) on the defect energy levels and formation energies was investigated. It was found that the 2D deformation is the most effective for pushing the defect levels towards the band edges and opening up the bandgap of the semiconductor, and hence may improve the performance of CdTe as a detector material. We studied the defect levels and their occupancies including Jahn-Teller distortions. The Jahn-Teller distorted configuration places the 2A(1)(a) defect level closer to the valence band and this defect level position coincides with the 'unknown deep donor' measured in some experiments. Partial densities of states and band structures have been analysed to understand the arrangement of the defect bonds.

  • 34.
    Shepidchenko, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mirbt, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Small hole polaron in CdTe: Cd-vacancy revisited2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 14509Article in journal (Other academic)
    Abstract [en]

    The characteristics of electronic states of Cd-vacancies in CdTe, an important semiconductor for various technological applications, are under debate both from theoretical and experimental points of view. Experimentally, the Cd-vacancy in its negative charge state is found to have C3v symmetry and a (−1/−2) transition level at 0.4 eV. Our first principles density functional calculations with hybrid functionals confirm for the first time these experimental findings. Additionally, we find that the C3v symmetry and the position of the (−1/−2) transition level are caused by the formation of a hole polaron localised at an anionic site around the vacancy.

  • 35.
    Stoller, R. E.
    et al.
    Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA..
    Tamm, A.
    Univ Tartu, Inst Technol, IMS Lab, EE-50411 Tartu, Estonia.;Los Alamos Natl Lab, Mat Sci & Technol Div, POB 1663, Los Alamos, NM 87544 USA..
    Beland, L. K.
    Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA..
    Samolyuk, G. D.
    Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA..
    Stocks, G. M.
    Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA..
    Caro, A.
    Los Alamos Natl Lab, Mat Sci & Technol Div, POB 1663, Los Alamos, NM 87544 USA..
    Slipchenko, L. V.
    Purdue Univ, Dept Chem, W Lafayette, IN 47906 USA..
    Osetsky, Yu N.
    Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA..
    Aabloo, A.
    Univ Tartu, Inst Technol, IMS Lab, EE-50411 Tartu, Estonia..
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wang, Y.
    Carnegie Mellon Univ, Pittsburgh Supercomp Ctr, Pittsburgh, PA 15213 USA..
    Impact of Short-Range Forces on Defect Production from High Energy Collisions2016In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 12, no 6, p. 2871-2879Article in journal (Refereed)
    Abstract [en]

    Primary radiation damage formation in solid materials typically involves collisions between atoms that have up to a few hundred keV of kinetic energy. Dining these collisions, the-distance between two colliding atoms can approach 0.05 nm. At such small atomic separations, force fields fitted-to equilibrium properties tend to significantly underestimate the potential-energy-of the colliding dieter. To enable molecular dynamics simulations of high-energy collisions, it is common practice to use a screened Coulomb, force field to describe the interactions and to smoothly join this to the equilibrium force field at a suitable interatomic spacing. However, there is,no accepted standard method for choosing the parameters used in the joining process, and our results prove that defect production is sensitive to how the force field's are linked. A new procedure is presented that involves the use of ab initio calculations to,determine the magnitude and spatial dependence of the pair interactions at intermediate distances, along with systematic criteria for choosing the joining parameters. Results are presented for the case of nickel, which demonstrate the use and validity of the procedure.

  • 36.
    Tamm, A.
    et al.
    Lawrence Livermore Natl Lab, Quantum Simulat Grp, Livermore, CA 94550 USA.
    Caro, M.
    Virginia Polytech Inst & State Univ, Dept Mech Engn, Arlington, VA 22033 USA.
    Caro, A.
    George Washington Univ, Ashburn, VA 20147 USA.
    Samolyuk, G.
    Oak Ridge Natl Lab, Mat Sci & Technol Div, POB 2009, Oak Ridge, TN 37831 USA.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Correa, A. A.
    Lawrence Livermore Natl Lab, Quantum Simulat Grp, Livermore, CA 94550 USA.
    Langevin Dynamics with Spatial Correlations as a Model for Electron-Phonon Coupling2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 18, article id 185501Article in journal (Refereed)
    Abstract [en]

    Stochastic Langevin dynamics has been traditionally used as a tool to describe nonequilibrium processes. When utilized in systems with collective modes, traditional Langevin dynamics relaxes all modes indiscriminately, regardless of their wavelength. We propose a generalization of Langevin dynamics that can capture a differential coupling between collective modes and the bath, by introducing spatial correlations in the random forces. This allows modeling the electronic subsystem in a metal as a generalized Langevin bath endowed with a concept of locality, greatly improving the capabilities of the two-temperature model. The specific form proposed here for the spatial correlations produces a physical wave-vector and polarization dependency of the relaxation produced by the electron-phonon coupling in a solid. We show that the resulting model can be used for describing the path to equilibration of ions and electrons and also as a thermostat to sample the equilibrium canonical ensemble. By extension, the family of models presented here can be applied in general to any dense system, solids, alloys, and dense plasmas. As an example, we apply the model to study the nonequilibrium dynamics of an electron-ion two-temperature Ni crystal.

  • 37.
    Tamm, A.
    et al.
    Los Alamos Natl Lab, Div Mat Sci & Technol, Los Alamos, NM 87545 USA.;Univ Tartu, Inst Technol, IMS Lab, EE-50411 Tartu, Estonia..
    Samolyuk, G.
    Oak Ridge Natl Lab, Div Mat Sci & Technol, Oak Ridge, TN USA..
    Correa, A. A.
    Lawrence Livermore Natl Lab, Livermore, CA 94550 USA..
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Aabloo, A.
    Univ Tartu, Inst Technol, IMS Lab, EE-50411 Tartu, Estonia..
    Caro, A.
    Los Alamos Natl Lab, Div Mat Sci & Technol, Los Alamos, NM 87545 USA..
    Electron-phonon interaction within classical molecular dynamics2016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 94, no 2, article id 024305Article in journal (Refereed)
    Abstract [en]

    We present a model for nonadiabatic classical molecular dynamics simulations that captures with high accuracy the wave-vector q dependence of the phonon lifetimes, in agreement with quantum mechanics calculations. It is based on a local view of the e-ph interaction where individual atom dynamics couples to electrons via a damping term that is obtained as the low-velocity limit of the stopping power of a moving ion in a host. The model is parameter free, as its components are derived from ab initio-type calculations, is readily extended to the case of alloys, and is adequate for large-scale molecular dynamics computer simulations. We also show how this model removes some oversimplifications of the traditional ionic damped dynamics commonly used to describe situations beyond the Born-Oppenheimer approximation.

  • 38.
    Tamm, Artur
    et al.
    Los Alamos Natl Lab, Mat Sci & Technol Div, Los Alamos, NM 87544 USA.;Univ Tartu, Inst Technol, IMS Lab, EE-50411 Tartu, Estonia..
    Aabloo, Alvo
    Univ Tartu, Inst Technol, IMS Lab, EE-50411 Tartu, Estonia..
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Stocks, Malcolm
    Oak Ridge Natl Lab, Oak Ridge, TN 54321 USA..
    Caro, Alfredo
    Los Alamos Natl Lab, Mat Sci & Technol Div, Los Alamos, NM 87544 USA..
    Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 99, p. 307-312Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. According to our study, the salient features for the ternary alloy are a negative SRO parameter between Ni-Cr and a positive between Cr-Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni-Cr and Ni-Fe pairs and positive for Cr-Cr and Fe-Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. The predicted SRO has an impact on point-defect energetics, electron-phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.

  • 39.
    Vegelius, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Kvashnina, Kristina
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Soroka, Inna
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Cu Kβ2,5 X-ray emission spectroscopy as a tool for characterization of monovalent copper compounds2012In: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 27, no 11, p. 1882-1888Article in journal (Refereed)
    Abstract [en]

    Cu Kβ 2,5 X-ray emission and resonant inelastic X-ray scattering measurements were performed on monovalent and divalent copper compounds. The data were compared with the results of local-density- approximation calculations. The methods were found to be efficient tools for studies of Cu 4p states in the valence band and for distinguishing between different monovalent copper compounds. This is of particular importance for the debate concerning copper corrosion in oxygen-free water.

  • 40.
    Vegelius, Johan R.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Kvashnina, K. O.
    Hollmark, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kvashnin, Y. O.
    Soroka, I. L.
    Werme, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Butorin, Sergei M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    X-ray Spectroscopic Study of Cu2S, CuS, and Copper Films Exposed to Na2S Solutions2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 42, p. 22293-22300Article in journal (Refereed)
    Abstract [en]

    The electronic structure of copper sulfides was studied using X-ray absorption at Cu K and L-2,L-3 and S L-2,L-3 edges and X-ray emission spectroscopy at S L-2,L-3 thresholds. The experimental data were compared with results of local density approximation calculations taking into account the calculated valence band contributions and core-level chemical shifts between inequivalent sites. The presence of divalent Cu was detected in CuS with X-ray absorption spectroscopy in the high-energy-resolution fluorescence detection (HERFD) mode. The S L-2,L-3 emission spectrum of CuS was found to be significantly broader than that of Cu2S due to contributions from inequivalent S sites. This difference in the spectral width was used to distinguish between sulfide species formed on the Cu foil exposed to Na2S solutions. The Cu-S interaction processes for Cu films of different thicknesses exposed to Na2S solutions were monitored in situ using X-ray absorption spectroscopy in the HERFD mode at the Cu K edge. It was found that Cu ions were diffusing in the sulfide and entering the solution. The rate at which Cu ions enter the solution via diffusion was estimated on the basis of the results for a 1000 angstrom thick film.

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