phq: a Fortran code to compute phonon quasiparticle properties and dispersions

ORAL

Abstract

Intrinsic thermal shifts of phonon frequencies due to lattice anharmonicity may be significant in solids at high temperatures. As such, the calculation of phonon dispersions incorporating anharmonic effects is critical for predictive studies of vibrational, thermodynamic, and lattice transport properties. Here we introduce the phq code to compute anharmonic phonon dispersions of crystals that combines molecular dynamics (MD) and lattice dynamics calculations. The method invokes the concept of phonon quasiparticles to extract thermal shifts and phonon lifetimes from velocity autocorrelation functions projected into normal modes sampled by MD simulations. With the renormalized frequencies, it is possible to construct an effective harmonic force constant matrix that allows us to calculate the anharmonic phonon dispersion over the whole Brillouin Zone. Due to the nature of phonon quasiparticles, this approach is applicable not only to simply crystals, but also to complex crystal structures with many atoms per primitive cell with extra effort. We demonstrate successful applications of this code to weakly and strongly anharmonic systems. In addition to temperature-dependent anharmonic phonon dispersions, the vibrational entropy and free energy at constant volume can also be obtained.

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Presenters

  • Zhen Zhang

    Department of Applied Physics and Applied Mathematics, Columbia University

Authors

  • Zhen Zhang

    Department of Applied Physics and Applied Mathematics, Columbia University

  • Dong-Bo Zhang

    College of Nuclear Science and Technology, Beijing Normal University, Beijing Computational Science Research Center, Simulation of Physical Systems Division, Beijing Computational Science Research Center, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, China

  • Tao Sun

    Key Laboratory of Computational Geodynamics, , University of Chinese Academy of Sciences, Beijing 100049, China, Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing 100088 China

  • Renata Wentzcovitch

    Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory (LDEO), and Applied Physics and Applied Mathematics (APAM), Columbia University in the City o, Department of Applied Physics and Applied Mathematics, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Columbia University, Department of Applied Physics and Applied Mathematics, Columbia University, Applied Physics and Applied Mathematics and Department of Earth and Environmental Sciences, Lamont Doherty Earth Observatory, Columbia University, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA., Department of Applied Physics and Applied Mathematics; Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, 10027, USA