The role of non-local exchange in the electronic structure of correlated oxides

TL;DR

This paper demonstrates that incorporating non-local exchange via hybrid functionals can accurately describe the electronic structure of correlated oxides, overcoming limitations of local and semilocal density functional approximations.

Contribution

The study shows that hybrid functionals, which include non-local exchange, can qualitatively match experimental electronic structures of correlated oxides without strong correlation effects.

Findings

Hybrid functionals improve band-structure predictions.

Non-local exchange reduces delocalization errors.

Hybrid functionals have both advantages and limitations for correlated oxides.

Abstract

We present a systematic study of the electronic structure of several prototypical correlated transition-metal oxides: VO2, V2O3, Ti2O3, LaTiO3, and YTiO3. In all these materials, in the low-temperature insulating phases the local and semilocal density approximations (LDA and GGA) of density-functional theory yield a metallic Kohn-Sham band structure. Here we show that, without invoking strong-correlation effects, the role of non-local exchange is essential to cure the LDA/GGA delocalization error and provide a band-structure description of the electronic properties in qualitative agreement with the experimental photoemission results. To this end, we make use of hybrid functionals that mix a portion of non-local Fock exchange with the local LDA exchange-correlation potential. Finally, we discuss the advantages and the shortcomings of using hybrid functionals for correlated transition-metal oxides.