Limitations of the hybrid functional approach to electronic structure of transition metal oxides

TL;DR

Hybrid functionals often fail to accurately describe the electronic structure of small gap transition metal oxides like VO2 near the Fermi surface without GW corrections, which are computationally expensive but necessary for accuracy.

Contribution

This paper demonstrates the limitations of hybrid functionals in modeling transition metal oxides and highlights the importance of GW corrections for accurate electronic structure calculations.

Findings

Hybrid functionals fail to capture Fermi-surface physics in VO2.

Fully self-consistent GW corrections improve wave function accuracy.

GW corrections are computationally demanding but necessary for correct results.

Abstract

During the last decade, ab initio methods to calculate electronic structure of materials based on hybrid functionals are increasingly becoming widely popular. In this Letter, we show that, in the case of small gap transition metal oxides, such as VO2, with rather subtle physics in the vicinity of the Fermi-surface, such hybrid functional schemes without the inclusion of "expensive" fully self-consistent GW corrections fail to yield this physics and incorrectly describe the features of the wave function of states near the Fermi-surface. While a fully self-consistent GW on top of hybrid functional approach does correct these wave functions as expected, and is found to be in general agreement with the results of a fully self-consistent GW approach based on semilocal functionals, it is much more computationally demanding as compared to the latter approach for the benefit of essentially the same results.