Precision benchmarks for solids: G0W0 calculations with different basis sets

TL;DR

This study compares G0W0 quasiparticle energy calculations across six crystalline solids using four different computational codes, analyzing the effects of basis sets and electron treatment methods on the accuracy of results.

Contribution

It provides a benchmark assessment of G0W0 calculations with various basis sets and electron treatments, highlighting the consistency and differences among multiple computational implementations.

Findings

KS-DFT band gaps agree within 0.1 eV across codes

G0W0 band gaps differ by 0.1-0.3 eV among codes

All-electron codes agree within 15 meV for KS-DFT

Abstract

The GW approximation within many-body perturbation theory is the state of the art for computing quasiparticle energies in solids. Typically, Kohn-Sham (KS) eigenvalues and eigenfunctions, obtained from a Density Functional Theory (DFT) calculation are used as a starting point to build the Green's function G and the screened Coulomb interaction W, yielding the one-shot G0W0 selfenergy if no further update of these quantities are made. Multiple implementations exist for both the DFT and the subsequent G0W0 calculation, leading to possible differences in quasiparticle energies. In the present work, the G0W0 quasiparticle energies for states close to the band gap are calculated for six crystalline solids, using four different codes: Abinit, exciting, FHI-aims, and GPAW. This comparison helps to assess the impact of basis-set types (planewaves versus localized orbitals) and the treatment of core and valence electrons (all-electron full potentials versus pseudopotentials). The impact of unoccupied states as well as the algorithms for solving the quasiparticle equation are also briefly discussed. For the KS-DFT band gaps, we observe good agreement between all codes, with differences not exceeding 0.1 eV, while the G0W0 results deviate on the order of 0.1-0.3 eV. Between all-electron codes (FHI-aims and exciting), the agreement is better than 15 meV for KS-DFT and, with one exception, about 0.1 eV for G0W0 band gaps.