Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 74: Focussed Session: Frontiers of Electronic Structure Theory VII (jointly with HL and TT)

O 74.11: Talk

Thursday, March 14, 2013, 18:30–18:45, H36

Core-electron forces within the FLAPW method — •Daniel Aaron Klüppelberg, Markus Betzinger, and Stefan Blügel — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany

The full-potential linearized augmented-plane-wave method (FLAPW) is an all-electron electronic-structure method based on density functional theory (DFT). Characteristic to the method is that space is divided into spheres around the atoms, so called ’muffin-tins’, and an interstitial region in between. Local orbitals can be used to describe semicore states within the valence-state formalism. It is established as an accurate tool for describing many properties of complex materials.

We address the occurrence of contributions to the forces due to core electrons described by wave functions having tails exceeding the muffin-tin boundary. Accurate forces are needed not only for relaxing the atomic structure to its ground state, but also in order to calculate precise phonon spectra via the finite-displacement method. We present a core-tail correction to the Pulay force term found by Yu et al. [1], implemented into the FLEUR code [2], which deals with the core electrons. This addition extends the known formula over the whole unit cell and therefore includes the complete force contribution coming from core states that extend beyond their muffin-tin. In this talk, we will present examples on the performance of this addition in comparison to the inclusion of local orbitals and the adjustment of the muffin-tin radii.

[1] R. Yu, D. Singh, and H. Krakauer, Phys. Rev. B 43, 6411 (1991)

[2] www.flapw.de