Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 37: Electronic structure theory I

O 37.6: Vortrag

Dienstag, 10. März 2026, 12:15–12:30, TRE/PHYS

Efficient all-electron implementation of the Bethe-Salpeter method using crystal symmetries — Jörn Stöhler, Stefan Blügel, and •Christoph Friedrich — Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany

We describe an implementation of the Bethe-Salpeter equation (BSE) method in the full-potential linearized augmented-plane-wave (FLAPW) method. As in most implementations, the BSE is solved by the diagonalization of a two-particle Hamiltonian matrix, whose dimension is proportional to the number of k points. Due to the large number of k points required to converge the spectra, the resulting matrix becomes large even for small unit cells. We describe a method that exploits the crystal symmetries to accelerate the construction and diagonalization of the two-particle Hamiltonian. In particular, we employ group theoretical tools to bring the Hamiltonian into block-diagonal form. It is shown that, in many cases, only one of the blocks needs to be taken into account, which leads to a considerable speedup of the diagonalization step. In the case of Si, for example, the dimension of the Hamiltonian is reduced by a factor of five, giving rise to a speedup factor of 125 in its diagonalization. The optical absorption spectrum calculated with a 60×60×60 k mesh is very close to the experimental spectrum. The code allows for the inclusion of spin-orbit coupling and is parallelized with the possibility of storing the Hamiltonian in distributed memory over many nodes. We also show results for LiF and the MoS₂ monolayer.

Keywords: Bethe-Salpeter equation; optical absorption spectroscopy; many-body perturbation theory; FLAPW method; ab initio