First-principles calculation of electronic excitations in solids with SPEX

TL;DR

SPEX is a software package for first-principles calculations of electronic excitations in solids, utilizing many-body perturbation theory and the FLAPW method to achieve high accuracy across diverse materials.

Contribution

It introduces SPEX, a new computational tool that efficiently performs quasiparticle and collective excitation calculations using advanced first-principles methods.

Findings

Accurate quasiparticle band structures within GW approximation.

Good agreement with experimental electron-energy-loss spectra.

Successful calculation of spin-wave spectra in ferromagnets.

Abstract

We describe the software package SPEX, which allows first-principles calculations of quasiparticle and collective electronic excitations in solids using techniques from many-body perturbation theory. The implementation is based on the full-potential linearized augmented-plane-wave (FLAPW) method, which treats core and valence electrons on an equal footing and can be applied to a wide range of materials, including transition metals and rare earths. After a discussion of essential features that contribute to the high numerical efficiency of the code, we present illustrative results for quasiparticle band structures calculated within the GW approximation for the electronic self-energy, electron-energy-loss spectra with inter- and intraband transitions as well as local-field effects, and spin-wave spectra of itinerant ferromagnets. In all cases the inclusion of many-body correlation terms leads to very good quantitative agreement with experimental spectroscopies.