Local Exchange-Correlation Potentials by Density Inversion in Solids

TL;DR

This study inverts electronic densities in solids to derive local exchange-correlation potentials, revealing their effectiveness in predicting band gaps and understanding the impact of different density functional approximations.

Contribution

It introduces a density inversion method to obtain local exchange-correlation potentials in solids, benchmarking their accuracy against standard functionals and experimental data.

Findings

LXC potentials from HF densities predict band gaps accurately.

HSE06 and PBE0 yield similar densities and potentials.

LXC potentials correct band flattening in LDA+U densities.

Abstract

Following Hollins et al. [J. Phys.: Condens. Matter 29, 04LT01 (2017)], we invert the electronic ground state densities for various semiconducting and insulating solids calculated using several density functional approximations within the generalised Kohn-Sham (GKS) scheme, Hartree-Fock (HF) theory and the LDA+$U$ method, and benchmark against standard (semi-)local functionals. The band structures from the resulting local exchange-correlation (LXC) Kohn-Sham potential for these densities are then compared with the band structures of the original GKS method. We find the LXC potential obtained from the HF density systematically predicts band gaps in good agreement with experiment, even in strongly correlated transition metal monoxides (TMOs). Furthermore, we find that the HSE06 and PBE0 hybrid functionals yield similar densities and LXC potentials, and in weakly correlated systems, these potentials are similar to PBE. For LDA+$U$ densities, the LXC potential effectively reverses the flattening of bands caused by over-localisation by a large Hubbard-$U$ value, while for meta-GGAs, we find only small differences between the GKS and LXC results demonstrating that the non-locality of meta-GGAs is weak.