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  • 1.
    Grånäs, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Timneanu, Nicusor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Eliah Dawod, Ibrahim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Trygg, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Femtosecond bond breaking and charge dynamics in ultracharged amino acids2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 14, article id 144307Article in journal (Refereed)
    Abstract [en]

    Historically, structure determination of nanocrystals, proteins, and macromolecules required the growth of high-quality crystals sufficiently large to diffract X-rays efficiently while withstanding radiation damage. The development of the X-ray free-electron laser has opened the path toward high resolution single particle imaging, and the extreme intensity of the X-rays ensures that enough diffraction statistics are collected before the sample is destroyed by radiation damage. Still, recovery of the structure is a challenge, in part due to the partial fragmentation of the sample during the diffraction event. In this study, we use first-principles based methods to study the impact of radiation induced ionization of six amino acids on the reconstruction process. In particular, we study the fragmentation and charge rearrangement to elucidate the time scales involved and the characteristic fragments occurring.

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  • 2.
    Hugosson, H. W
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Ruban, A. V
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Abrikosov, I. A
    Surface energies and work functions of the transition metal carbides2004In: Surface Science, Vol. 557, no 1-3, p. 243-254Article in journal (Refereed)
    Abstract [en]

    We have performed an ab initio study of the surface energies, surface electronic structures and work functions for the (1 0 0) surface of the, existent and hypothetical, cubic 3d (Sc–Cu), 4d (Zr–Ag) and 5d (La–Au) transition metal carbides. The calculated surface energies have been compared to predictions using a so-called bond-cutting model and a model based on the so-called bonding energies. The absolute values and rough trends of the surface energies are fairly well predicted within the simple bond-cutting model, as compared to fully self-consistent calculations, while both trends and absolute values are well reproduced within the bonding energy model. The electronic structure (densities of states) of the transition metal carbides at the surface and in the bulk have been calculated. The trends are discussed in relation to the behavior of the surface energy and the work function across the series.

  • 3.
    Isaeva, Leyla
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Souvatzis, Petros
    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.
    Lashley, Jason C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Lattice dynamics of cubic AuZn from first principles2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 10, p. 104101-Article in journal (Refereed)
    Abstract [en]

    We study the mechanism of the B2 -> R martensitic transformation in the shape memory alloy AuZn by means of first-principles theory. Phonon anomalies in the TA(2) acoustic branch along the Gamma-M [xi,xi,0] direction associated with a structural transformation are observed. The calculated Fermi surface of the B2 phase of AuZn reveals large portions nested with each other by a translation through a vector q = 1/3[1,1,0] associated with the soft mode. In addition, we find that the B2 phase can be stabilized by pressure in the low-temperature limit. The energetic barrier for the B2 -> R transition is 2 mRy and appears to be near a critical point.

  • 4. Kanchana, V.
    et al.
    Vaitheeswaran, G.
    Souvatzis, Petros
    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.
    Lebegue, S.
    Density functional study of the electronic structure and lattice dynamics of SrCl22010In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 22, no 44, p. 445402-Article in journal (Refereed)
    Abstract [en]

    A theoretical study of the structural, electronic, optical and lattice dynamical properties of SrCl2 in the cubic fluorite structure has been performed using first-principles calculations. The calculated ground state and elastic properties are in good agreement with the experiments. The calculated band gap is underestimated within the generalized gradient approximation for the exchange and correlation functional. GW calculations have been performed in order to improve the band gap and good agreement with the experiment is obtained. The phonon dispersion relations are discussed in detail in addition to the ground state and elastic properties. Also, the optical properties are computed with DFT corrected by the GW approximation.

  • 5.
    Koči, Love
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ma, Y.
    Oganov, A. R.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Elasticity study of the superconducting metals V, Nb, Ta, Mo and W at high pressure2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Physical Review B, Vol. 77, no 21, p. 214101-Article in journal (Refereed)
    Abstract [en]

    First-principles calculations have been performed for V, Nb, Ta, Mo, and W. The recently discovered bcc -> , rhombohedral transition for vanadium [Phys. Rev. Lett. 98, 085502 (2007)] was confirmed as the mechanical instability of c(44) was found at P=80 GPa. Furthermore, the c(11), c(12), and c(44) constants for the group-V elements showed erratic behaviors whereas the constants for the group-VI elements were monotonically increasing with pressure. The metals were analyzed with Fermi surface calculations, showing shrinking nesting vectors with pressure for V, Nb, and Ta but were not seen for Mo and W. From electronic topological transition contributions, a critical energy closely situated to the Fermi level for vanadium could be the reason why the elastic constants of V and Nb were difficult to reproduce at ambient pressure.

  • 6.
    Luo, Wei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johansson, Börje
    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.
    Arapan, Sergiu
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Katsnelson, Mikhail I.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Dynamical stability of body center cubic iron at the Earth's core conditions2010In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 107, no 22, p. 9962-9964Article in journal (Refereed)
    Abstract [en]

    Here, using self-consistent ab initio lattice dynamical calculations that go beyond the quasiharmonic approximation, we show that the high-pressure high-temperature bcc-Fe phase is dynamically stable. In this treatment the temperature-dependent phonon spectra are derived by exciting all the lattice vibrations, in which the phonon-phonon interactions are considered. The high-pressure and high-temperature bcc-Fe phase shows standard bcc-type phonon dispersion curves except for the transverse branch, which is overdamped along the high symmetry direction Gamma-N, at temperatures below 4,500 K. When lowering the temperature down to a critical value T-C, the lattice instability of the bcc structure is reached. The pressure dependence of this critical temperature is studied at conditions relevant for the Earth's core.

  • 7.
    Råsander, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Höglund, Andreas
    Eriksson, Olle
    Elasticity model for the calculation of lattice parameters in multilayer structuresManuscript (Other academic)
  • 8.
    Råsander, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Höglund, Andreas
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Elasticity model for the evaluation of structural parameters in multilayer systems with applications to transition metal and Si-based multilayers2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 12, p. 125424-Article in journal (Refereed)
    Abstract [en]

    In this paper we present and evaluate a model based on elasticity theory for the calculation of in- and out-of-plane lattice parameters in multilayer systems, which can be used for a wide selection of multilayers. The model assumes perfect lattice matching at the interface between the different components in the multilayer. The only input is the knowledge of the elastic and lattice constants of the different components in the bulk as well as the relative thickness between the components in the multilayer. We show that the model is in good agreement when compared to first-principles theory calculations and also that there is good agreement between the model and experimental structures for several multilayer systems. The model is also shown to be more appropriate in describing thicker multilayers with larger periodicities such that the lattice constants in the system are independent on the periodicity. Furthermore, we provide results for the lattice parameters for a large body of multilayers based on transition metals and semiconducting materials.

  • 9.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Electronic Structure and Lattice Dynamics of Elements and Compounds2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The elastic constants of Mg(1-x)AlxB2 have been calculated in the regime 0<x<0.25. The calculations show that the ratio, B/G, between the bulk- and the shear-modulus stays well below the empirical ductility limit, 1.75, for all concentrations, indicating that the introduction of Al will not change the brittle behaviour of the material considerably. Furthermore, the tetragonal elastic constant C’ has been calculated for the transition metal alloys Fe-Co, Mo-Tc and W-Re, showing that if a suitable tuning of the alloying is made, these materials have a vanishingly low C'. Thermal expansion calculations of the 4d transition metals have also been performed, showing good agreement with experiment with the exception of Nb and Mo. The calculated phonon dispersions of the 4d metals all give reasonable agreement with experiment. First principles calculations of the thermal expansion of hcp Ti have been performed, showing that this element has a negative thermal expansion along the c-axis which is linked to the closeness of the Fermi level to an electronic topological transition. Calculations of the EOS of fcc Au give support to the suggestion that the ruby pressure scale might underestimate pressures with ~10 GPa at pressures ~150 GPa. The high temperature bcc phase of the group IV metals has been calculated with the novel self-consistent ab-initio dynamical (SCAILD) method. The results show good agreement with experiment, and the free energy resolution of < 1 meV suggests that this method might be suitable for calculating free energy differences between different crystallographic phases as a function of temperature.

    List of papers
    1. Elastic properties of Mg(1-x)AlxB2 from first principles theory
    Open this publication in new window or tab >>Elastic properties of Mg(1-x)AlxB2 from first principles theory
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    2004 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, no 29, p. 5241-5250Article in journal (Refereed) Published
    Abstract [en]

    Elastic properties of Mg(1−x)AlxB2 have been studied from first principles. The elastic constants (c11, c12, c13, c33 and c55) have been calculated, in the regime of x = 0 to 0.25. From these calculations the ratio between the bulk modulus and shear modulus (B/G) as well as the ratio between the two directional bulk moduli (Ba/Bc) have been evaluated. Our calculations show that the ratio Ba/Bc decreases monotonically as the aluminium content is increased, whereas the ratio B/G is well below the empirical ductility limit, 1.75, for all concentrations. In addition, we analyse the electronic structure and the nature of the chemical bonding, using the balanced crystal orbital overlap population (BCOOP) (Grechnev et al 2003 J. Phys.: Condens. Matter 15 7751) and the charge densities. Our analysis suggests that, while aluminium doping decreases the elastic anisotropy of MgB2 in the a and c directions, it will not change the brittle behaviour of the material considerably. 

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-92691 (URN)10.1088/0953-8984/16/29/015 (DOI)
    Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-14Bibliographically approved
    2. First-principles prediction of superplastic transition-metal alloys
    Open this publication in new window or tab >>First-principles prediction of superplastic transition-metal alloys
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    2004 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 1, p. 012201-Article in journal (Refereed) Published
    Abstract [en]

    Superplastic transition metal alloys and compounds are predicted from first principles calculations. Provided a suitable tuning of the alloying is done, materials with vanishingly low shear modulus C[prime] have recently been identified among the 3d, 4d, and 5d elements if the valence electron average number is close to 4.24 (i.e., Ti-Ta-Nb-V-Zr-O and Ti-Nb-Ta-Zr-O alloys). The vanishingly low C[prime] elastic constant of these bcc alloys is, according to the joint experimental and theoretical studies [T. Saito et al., Science 300, 464 (2003)], the crucial material parameter that is responsible for the superplasticity. We predict here, using first principles calculations, that superplastic alloys should also be found for alloys with drastically different valence electron concentrations, i.e., for W-Re-, W-Tc-, Mo-Re-, Mo-Tc-, and Fe-Co-based alloys.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-96174 (URN)10.1103/PhysRevB.70.012201 (DOI)000222996300003 ()
    Available from: 2007-09-13 Created: 2007-09-13 Last updated: 2017-12-14Bibliographically approved
    3. Calculation of the equation of state of fcc Au from first principles
    Open this publication in new window or tab >>Calculation of the equation of state of fcc Au from first principles
    2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, no 5, p. 054110-Article in journal (Refereed) Published
    Abstract [en]

    The electron and phonon contributions to the free energy of gold are calculated from a first-principles method. From the free energy the equation of state (EOS) along with the shock Hugoniot with initial conditions at ambient pressure and room temperature are calculated. The results show good agreement with the corresponding experimental EOS and Hugoniot up to compressions of V/V-0=0.65-i.e., up to the solid-liquid phase transition in the Hugoniot. Optimal agreement between experiment and theory is obtained after a small adjustment of the calculated equilibrium lattice constant to the experimental lattice constant. (the correction is of the order of a few percent). The current calculations are consistent with recent suggestions of an underestimation of the pressures obtained with the ruby pressure scale R-1 line.

    Keywords
    ELASTIC CONSTANTS, PRESSURE GAUGE, GOLD, CALIBRATION, TEMPERATURE, SYSTEMS, AG, CU
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96175 (URN)10.1103/PhysRevB.73.054110 (DOI)
    Available from: 2007-09-13 Created: 2007-09-13 Last updated: 2021-01-14Bibliographically approved
    4. Anomalous Thermal Expansion in α-Titanium
    Open this publication in new window or tab >>Anomalous Thermal Expansion in α-Titanium
    2007 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, no 1, p. 015901-Article in journal (Refereed) Published
    Abstract [en]

    We provide a complete quantitative explanation for the anisotropic thermal expansion of hcp Ti at low temperature. The observed negative thermal expansion along the c axis is reproduced theoretically by means of a parameter free theory which involves both the electron and phonon contributions to the free energy. The thermal expansion of titanium is calculated and found to be negative along the c axis for temperatures below ∼170 K, in good agreement with observations. We have identified a saddle point van Hove singularity near the Fermi level as the main reason for the anisotropic thermal expansion in α-titanium.

    Keywords
    Thermal expansion; thermomechanical effects, Phonon states and bands, normal modes, and phonon dispersion, Transition metals and alloys
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96176 (URN)10.1103/PhysRevLett.99.015901 (DOI)000247819900024 ()
    Available from: 2007-09-13 Created: 2007-09-13 Last updated: 2017-12-14Bibliographically approved
    5. Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory
    Open this publication in new window or tab >>Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory
    2008 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 9, p. 095901-Article in journal (Refereed) Published
    Abstract [en]

    Conventional methods to calculate the thermodynamics of crystals evaluate the harmonic phonon spectra and therefore do not work in frequent and important situations where the crystal structure is unstable in the harmonic approximation, such as the body-centered cubic (bcc) crystal structure when it appears as a high-temperature phase of many metals. A method for calculating temperature dependent phonon spectra self-consistently from first principles has been developed to address this issue. The method combines concepts from Born's interatomic self-consistent phonon approach with first principles calculations of accurate interatomic forces in a supercell. The method has been tested on the high-temperature bcc phase of Ti, Zr, and Hf, as representative examples, and is found to reproduce the observed high-temperature phonon frequencies with good accuracy.

    Keywords
    Thermal expansion; thermomechanical effects, Phonon states and bands, normal modes, and phonon dispersion, Transition metals and alloys
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96177 (URN)10.1103/PhysRevLett.100.095901 (DOI)000253764500047 ()
    Available from: 2007-09-13 Created: 2007-09-13 Last updated: 2017-12-14Bibliographically approved
    6. Ab-initio calculations of the phonon spectrum and the thermal expansion for the 4d metals
    Open this publication in new window or tab >>Ab-initio calculations of the phonon spectrum and the thermal expansion for the 4d metals
    (English)In: Phys. Rev. B, p. 1-7Article in journal (Refereed) Submitted
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96178 (URN)
    Available from: 2007-09-13 Created: 2007-09-13 Last updated: 2012-04-01Bibliographically approved
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  • 10.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Phonon lifetimes from first-principles self-consistent lattice dynamics2011In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 44, p. 445401-Article in journal (Refereed)
    Abstract [en]

    Phonon lifetime calculations from first principles usually rely on time-consuming molecular dynamics calculations, or density functional perturbation theory where the zero-temperature crystal structure is assumed to be dynamically stable. Here is presented a new and effective method for calculating phonon lifetimes from first principles. This method is not limited to crystallographic phases stable at 0 K and provides a scheme more effective than most corresponding molecular dynamics calculations. The method is based on the recently developed self-consistent ab initio lattice dynamical method and is here tested by calculating the bcc phase phonon lifetimes of Li, Na, Ti and Zr as representative examples.

  • 11.
    Souvatzis, Petros
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV.
    Studies of elastic and structural properties of alloys from first principles calculations2004Licentiate thesis, monograph (Other scientific)
  • 12.
    Souvatzis, Petros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Uquantchem: A versatile and easy to use quantum chemistry computational software2014In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 185, no 1, p. 415-421Article in journal (Refereed)
    Abstract [en]

    In this paper we present the Uppsala Quantum Chemistry package (UQUANTCHEM), a new and versatile computational platform with capabilities ranging from simple Hartree-Fock calculations to state of the art First principles Extended Lagrangian Born-Oppenheimer Molecular Dynamics (XL-BOMD) and diffusion quantum Monte Carlo (DMC). The UQUANTCHEM package is distributed under the general public license and can be directly downloaded from the code web-site (http://www.anst.uu.se/pesou087/DOWNLOADUQUANTCHEM/DOWNLOAD-UQUANTCHEM/DOWNLOAD-SITE-UQUANTCHEM.html) [1]. Together with a presentation of the different capabilities of the uquantchem code and a more technical discussion on how these capabilities have been implemented, a presentation of the user-friendly aspect of the package on the basis of the large number of default settings will also be presented. Furthermore, since the code has been parallelized within the framework of the message passing interface (MPI), the timing of some benchmark calculations are reported to illustrate how the code scales with the number of computational nodes for different levels of chemical theory. Program summary Program title: Uquantchem Catalogue identifier: AEQY_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEQY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 2082722. No. of bytes in distributed program, including test data, etc.: 15501085 Distribution format: tar.gz Programming language: Fortran90. Computer: The program should work on any system with a F90 compiler. The code has been tested with the Intel and gfortran compilers. Operating system: Unix/Linux. Has the code been vectorized or parallelized?: The distribution file contains both a serial and a parallel version of the program. Number of processors used, 2-2000. RAM: 2 GB for molecules consisting of <10 atoms. Classification: 16.10. External routines: The Lapack and Bias libraries are required but are included in the distribution file. MP1 is required for the parallel version. Nature of problem:. Electronic structure, total energy and force calculation of molecules. Solution method: Basis-set expansion in terms of contracted Gaussian functions is used to solve the Hartree-Fock or the Kohn-Sham equations self consistently. Running time: From a couple of seconds up to several days depending on the size of the molecule, the level of theory used and the number of Processors used.

  • 13.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Arapan, Sergiu
    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.
    Katsnelson, M. I.
    Temperature-driven alpha-to-beta phase transformation in Ti, Zr and Hf from first-principles theory combined with lattice dynamics2011In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 96, no 6, p. 66006-Article in journal (Refereed)
    Abstract [en]

    Lattice dynamical methods used to predict phase transformations in crystals typically deal with harmonic phonon spectra and are therefore not applicable in important situations where one of the competing crystal structures is unstable in the harmonic approximation, such as the bcc structure involved in the hcp-to-bcc martensitic phase transformation in Ti, Zr and Hf. Here we present an expression for the free energy that does not suffer from such shortcomings, and we show by self-consistent ab initio lattice dynamical calculations (SCAILD), that the critical temperature for the hcp-to-bcc phase transformation in Ti, Zr and Hf, can be effectively calculated from the free-energy difference between the two phases. This opens up the possibility to study quantitatively, from first-principles theory, temperature-induced phase transitions.

  • 14.
    Souvatzis, Petros
    et al.
    Theoretical Division, Los Alamos National Laboratory.
    Björkman, Torbjörn
    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.
    Andersson, Per
    Totalförsvarets forskningsinstitut.
    Katsnelson, M. I.
    Institute for Molecules and Materials, Radboud University Nijmegen.
    Rudin, S. P.
    Theoretical Division, Los Alamos National Laboratory.
    Dynamical stabilization of the body centered cubic phase in lanthanum and thorium by phonon–phonon interaction2009In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 21, no 17, p. 175402-Article in journal (Refereed)
    Abstract [en]

    A recently developed self-consistent ab initio lattice dynamical method has been applied to the high temperature body centered cubic (bcc) phase of La and Th, which are dynamically unstable at low temperatures. The bcc phase of these metals is found to be stabilized by phonon–phonon interactions. The calculated high temperature phonon frequencies for La are found to be in good agreement with the corresponding experimental data.

  • 15.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Delin, Anna
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Calculation of the equation of state of fcc Au from first principles2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, no 5, p. 054110-Article in journal (Refereed)
    Abstract [en]

    The electron and phonon contributions to the free energy of gold are calculated from a first-principles method. From the free energy the equation of state (EOS) along with the shock Hugoniot with initial conditions at ambient pressure and room temperature are calculated. The results show good agreement with the corresponding experimental EOS and Hugoniot up to compressions of V/V-0=0.65-i.e., up to the solid-liquid phase transition in the Hugoniot. Optimal agreement between experiment and theory is obtained after a small adjustment of the calculated equilibrium lattice constant to the experimental lattice constant. (the correction is of the order of a few percent). The current calculations are consistent with recent suggestions of an underestimation of the pressures obtained with the ruby pressure scale R-1 line.

  • 16.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Ab initio calculations of the phonon spectra and the thermal expansion coefficients of the 4d metals2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 2, p. 024110-Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    We have performed first principles calculations of the phonon spectra of the 4d transition metals with the so-called supercell method and found good agreement with observations. Furthermore, the electron and phonon contributions to the free energy for the 4d metals have been calculated from a first principles method. From the free energy, the thermal expansion of the metals is calculated. The calculated thermal expansion coefficients for the cubic elements are in overall good agreement with the experiment when the local density approximation is employed, while the generalized gradient approximation calculations yield a discrepancy as big as ~30%. For the hexagonal elements, reasonable agreement is found between calculations and experiment for the volume thermal expansion at temperatures 200 K < T < 300 K.

  • 17.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Ab-initio calculations of the phonon spectrum and the thermal expansion for the 4d metalsIn: Phys. Rev. B, p. 1-7Article in journal (Refereed)
  • 18.
    Souvatzis, Petros
    et al.
    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.
    Rudin, S. P.
    The self-consistent ab initio lattice dynamical method2009In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 44, no 3, p. 888-894Article in journal (Refereed)
    Abstract [en]

    We describe a method for calculating temperature dependent phonon spectra self consistently from first principles. The method combines concepts from Born's self-consistent phonon approach with ab initio calculations of accurate interatomic forces in a supercell. Test calculations on the high temperature bcc phase of Ti, Zr, Hf, Sc and Y. as representative examples, reproduce the observed high temperature phonon frequencies with good accuracy. By use of an embedded atom potential we demonstrate the method's relevance in calculating approximate critical temperatures of solid-solid phase transitions for the hcp to bcc transition in Zr.

  • 19.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Katsnelson, Mikhail
    Anomalous Thermal Expansion in α-Titanium2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, no 1, p. 015901-Article in journal (Refereed)
    Abstract [en]

    We provide a complete quantitative explanation for the anisotropic thermal expansion of hcp Ti at low temperature. The observed negative thermal expansion along the c axis is reproduced theoretically by means of a parameter free theory which involves both the electron and phonon contributions to the free energy. The thermal expansion of titanium is calculated and found to be negative along the c axis for temperatures below ∼170 K, in good agreement with observations. We have identified a saddle point van Hove singularity near the Fermi level as the main reason for the anisotropic thermal expansion in α-titanium.

  • 20.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Katsnelson, Mikhail
    Rudin, Sven
    Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 9, p. 095901-Article in journal (Refereed)
    Abstract [en]

    Conventional methods to calculate the thermodynamics of crystals evaluate the harmonic phonon spectra and therefore do not work in frequent and important situations where the crystal structure is unstable in the harmonic approximation, such as the body-centered cubic (bcc) crystal structure when it appears as a high-temperature phase of many metals. A method for calculating temperature dependent phonon spectra self-consistently from first principles has been developed to address this issue. The method combines concepts from Born's interatomic self-consistent phonon approach with first principles calculations of accurate interatomic forces in a supercell. The method has been tested on the high-temperature bcc phase of Ti, Zr, and Hf, as representative examples, and is found to reproduce the observed high-temperature phonon frequencies with good accuracy.

  • 21.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Katsnelson, Mikhail
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Simak, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Mohn, Peter
    First-principles prediction of superplastic transition-metal alloys2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 1, p. 012201-Article in journal (Refereed)
    Abstract [en]

    Superplastic transition metal alloys and compounds are predicted from first principles calculations. Provided a suitable tuning of the alloying is done, materials with vanishingly low shear modulus C[prime] have recently been identified among the 3d, 4d, and 5d elements if the valence electron average number is close to 4.24 (i.e., Ti-Ta-Nb-V-Zr-O and Ti-Nb-Ta-Zr-O alloys). The vanishingly low C[prime] elastic constant of these bcc alloys is, according to the joint experimental and theoretical studies [T. Saito et al., Science 300, 464 (2003)], the crucial material parameter that is responsible for the superplasticity. We predict here, using first principles calculations, that superplastic alloys should also be found for alloys with drastically different valence electron concentrations, i.e., for W-Re-, W-Tc-, Mo-Re-, Mo-Tc-, and Fe-Co-based alloys.

  • 22.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Legut, Dominik
    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.
    Katsnelson, Mikhail I.
    Ab initio study of interacting lattice vibrations and stabilization of the beta phase in Ni-Ti shape-memory alloy2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 9, p. 092201-Article in journal (Refereed)
    Abstract [en]

    Lattice dynamical methods used to predict phase transformations in crystals typically evaluate the harmonic phonon spectra and therefore do not work in frequent and important situations where the crystal structure is unstable in the harmonic approximation, such as the beta structure when it appears as a high-temperature phase of the shape memory alloy Ni-Ti. Here it is shown by self-consistent ab initio lattice dynamical calculations that the critical temperature for the premartensitic R-to-beta phase transformation in Ni-Ti can be effectively calculated with good accuracy, and that the beta phase is a result primarily of the stabilizing interaction between different lattice vibrations.

  • 23.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Niklasson, Anders M. N.
    Extended Lagrangian Born-Oppenheimer molecular dynamics in the limit of vanishing self-consistent field optimization2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 139, no 21, p. 214102-Article in journal (Refereed)
    Abstract [en]

    We present an efficient general approach to first principles molecular dynamics simulations based on extended Lagrangian Born-Oppenheimer molecular dynamics [A. M. N. Niklasson, Phys. Rev. Lett. 100, 123004 (2008)] in the limit of vanishing self-consistent field optimization. The reduction of the optimization requirement reduces the computational cost to a minimum, but without causing any significant loss of accuracy or long-term energy drift. The optimization-free first principles molecular dynamics requires only one single diagonalization per time step, but is still able to provide trajectories at the same level of accuracy as "exact," fully converged, Born-Oppenheimer molecular dynamics simulations. The optimization-free limit of extended Lagrangian Born-Oppenheimer molecular dynamics therefore represents an ideal starting point for robust and efficient first principles quantum mechanical molecular dynamics simulations.

  • 24.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Niklasson, Anders M. N.
    First principles molecular dynamics without self-consistent field optimization2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 4, p. 044117-Article in journal (Refereed)
    Abstract [en]

    We present a first principles molecular dynamics approach that is based on time-reversible extended Lagrangian Born-Oppenheimer molecular dynamics [A. M. N. Niklasson, Phys. Rev. Lett. 100, 123004 (2008)] in the limit of vanishing self-consistent field optimization. The optimization-free dynamics keeps the computational cost to a minimum and typically provides molecular trajectories that closely follow the exact Born-Oppenheimer potential energy surface. Only one single diagonalization and Hamiltonian (or Fockian) construction are required in each integration time step. The proposed dynamics is derived for a general free-energy potential surface valid at finite electronic temperatures within hybrid density functional theory. Even in the event of irregular functional behavior that may cause a dynamical instability, the optimization-free limit represents a natural starting guess for force calculations that may require a more elaborate iterative electronic ground state optimization. Our optimization-free dynamics thus represents a flexible theoretical framework for a broad and general class of ab initio molecular dynamics simulations. (C) 2014 AIP Publishing LLC.

  • 25.
    Souvatzis, Petros
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Theoretical Magnetism. Theoretical magnetism.
    Osorio-Guillen, Jorge
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Theoretical Magnetism.
    Elastic properties of Mg(1-x)AlxB22004In: Journal of Physics: Condensed Matter, ISSN 0953-8984, Vol. 16, no 29, p. 5241–5250-Article in journal (Refereed)
    Abstract [en]

    Elastic properties ofMg(1−x)AlxB2 have been studied from first principles. The

    elastic constants (c11, c12, c13, c33 and c55) have been calculated, in the regime

    of x = 0 to 0.25. From these calculations the ratio between the bulk modulus

    and shear modulus (B/G) as well as the ratio between the two directional

    bulk moduli (Ba/Bc) have been evaluated. Our calculations show that the

    ratio Ba/Bc decreases monotonically as the aluminium content is increased,

    whereas the ratio B/G is well below the empirical ductility limit, 1.75, for all

    concentrations. In addition, we analyse the electronic structure and the nature

    of the chemical bonding, using the balanced crystal orbital overlap population

    (BCOOP) (Grechnev et al 2003 J. Phys.: Condens. Matter 15 7751) and the

    charge densities. Our analysis suggests that, while aluminium doping decreases

    the elastic anisotropy of MgB2 in the a and c directions, it will not change the

    brittle behaviour of the material considerably.

    (Some figures in this article are in colour only in the electronic version)

  • 26.
    Souvatzis, Petros
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Osorio-Guillén, Jorge Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Grechnev, Alexei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Elastic properties of Mg(1-x)AlxB2 from first principles theory2004In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, no 29, p. 5241-5250Article in journal (Refereed)
    Abstract [en]

    Elastic properties of Mg(1−x)AlxB2 have been studied from first principles. The elastic constants (c11, c12, c13, c33 and c55) have been calculated, in the regime of x = 0 to 0.25. From these calculations the ratio between the bulk modulus and shear modulus (B/G) as well as the ratio between the two directional bulk moduli (Ba/Bc) have been evaluated. Our calculations show that the ratio Ba/Bc decreases monotonically as the aluminium content is increased, whereas the ratio B/G is well below the empirical ductility limit, 1.75, for all concentrations. In addition, we analyse the electronic structure and the nature of the chemical bonding, using the balanced crystal orbital overlap population (BCOOP) (Grechnev et al 2003 J. Phys.: Condens. Matter 15 7751) and the charge densities. Our analysis suggests that, while aluminium doping decreases the elastic anisotropy of MgB2 in the a and c directions, it will not change the brittle behaviour of the material considerably. 

  • 27. Söderlind, Per
    et al.
    Grabowski, B.
    Yang, L.
    Landa, A.
    Björkman, T.
    Souvatzis, Petros
    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.
    High-temperature phonon stabilization of γ-uranium from relativistic first-principles theory2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, no 6, p. 060301-Article in journal (Refereed)
    Abstract [en]

    A microscopic explanation for temperature stabilization of the body-centered cubic (bcc) phase in the actinide metals is proposed. We show that for a prototype actinide, uranium, phonon-phonon interaction promotes bcc gamma-U when heated, even though at low temperatures, it is mechanically a strongly unstable phase. Utilizing the recently developed self-consistent ab initio lattice dynamics (SCAILD) scheme in conjunction with highly accurate and fully relativistic density functional theory we obtain phonon dispersion and density of states that compare well with data acquired from inelastic neutron-scattering experiments. The investigation thus establishes that high-temperature lattice dynamics can be modeled from ab initio theory even for complex materials with substantial electron correlation including the actinides.

1 - 27 of 27
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