Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 92: Electronic Structure Theory

O 92.3: Vortrag

Freitag, 5. April 2019, 11:00–11:15, H5

All-electron FLAPW Realization of DFPT: 2nd-order Quantities and Dynamical Matrix — •Christian-Roman Gerhorst, Markus Betzinger, Daniel Aaron Klüppelberg, Gustav Bihlmayer, and Stefan Blügel — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

The dynamical properties of atoms in the harmonic approximation are obtained by solving an eigenvalue problem of the dynamical matrix, which is related to the second-order variation of the total energy with respect to the atom displacement. We determine the dynamical matrix employing the all-electron full-potential linearized augmented plane-wave (FLAPW) method, as realized in the FLEUR (www.flapw.de) code, using the density functional perturbation theory (DFPT). The formulation and realization of the DFPT in the LAPW basis is a non-trivial task, as it entails a much more sophisticated formalism compared to plane-wave codes. Due to the atom-position dependence and the discontinuities at the boundaries of the domain-wise defined LAPW basis, so-called Pulay and surface terms emerge making the realization of DFPT in FLAPW a challenge. In this contribution, we start from a brief presentation of these terms within the self-consistent solution of the Sternheimer equation, which delivers all required first-order quantities for the dynamical matrix. We will put an emphasis on how to treat the second-order changes of the external potential, the second-order variations of the wavefunction, as well as the basis-induced Pulay terms in the dynamical matrix setup, and show first results.