Quasiparticle band structure based on a generalized Kohn-Sham scheme

TL;DR

This paper compares various generalized Kohn-Sham schemes as starting points for quasiparticle calculations, showing that certain schemes improve band gap predictions especially in challenging materials with shallow d bands.

Contribution

It demonstrates that using a gKS scheme, particularly HSE03, as a starting point enhances the accuracy of quasiparticle band structures in complex materials.

Findings

gKS schemes improve quasiparticle band gap predictions

HSE03 functional provides results close to experimental data

Self-consistency effects in GW calculations are analyzed

Abstract

We present a comparative full-potential study of generalized Kohn-Sham schemes (gKS) with explicit focus on their suitability as starting point for the solution of the quasiparticle equation. We compare $G_0W_0$ quasiparticle band structures calculated upon LDA, sX, HSE03, PBE0, and HF functionals for exchange and correlation (XC) for Si, InN and ZnO. Furthermore, the HSE03 functional is studied and compared to the GGA for 15 non-metallic materials for its use as a starting point in the calculation of quasiparticle excitation energies. For this case, also the effects of selfconsistency in the $GW$ self-energy are analysed. It is shown that the use of a gKS scheme as a starting point for a perturbative QP correction can improve upon the deficiencies found for LDA or GGA staring points for compounds with shallow $d$ bands. For these solids, the order of the valence and conduction bands is often inverted using local or semi-local approximations for XC, which makes perturbative $G_0W_0$ calculations unreliable. The use of a gKS starting point allows for the calculation of fairly accurate band gaps even in these difficult cases, and generally single-shot $G_0W_0$ calculations following calculations using the HSE03 functional are very close to experiment.