Dresden 2014 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory
O 36.90: Poster
Tuesday, April 1, 2014, 18:30–22:00, P1
Forces in the FLAPW method revisited — •Aaron Klüppelberg, Markus Betzinger, and Stefan Blügel — Peter Grünberg Institut & Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
Density functional theory (DFT) is nowadays the workhorse for simulating the electronic and geometric structure of real materials. Forces, i.e., the derivatives of the DFT total energy with respect to atomic positions, are indispensable for any structural optimization. Accurate forces, moreover, enable the calculation of phonon spectra using the finite displacement method
and of subsequent quantities such as electron- and magnon-phonon interaction.
We analyze the accuracy of the force computed within the all-electron full-potential linearized augmented plane-wave (FLAPW) method as realized in the FLEUR code [1] according to the formalism of Yu et al. [2]. As one criterion for the accuracy we employ the drift-force, i.e., the sum of all atomic forces in the unit cell, which should strictly vanish. Another criterion is the quality of the symmetry of the force-constant matrix. We show that both criteria can be fulfilled to an accuracy of 1µHtr/a0 only if (a) the core-electron tails are properly taken into account and (b) a large angular momentum cut-off is applied. We propose a refined formulation of the force that cures the aforementioned demands on the LAPW setup to a great extent. As an example, we present results for MgO and EuTiO3.
www.flapw.de
R. Yu, D. Singh, and H. Krakauer, Phys. Rev. B 43, 6411 (1991).