Systematic beyond-DFT study of binary transition metal oxides

Subhasish Mandal,David Vanderbilt,Kristjan Haule,Karin M Rabe

doi:10.1038/s41524-019-0251-7

Abstract

Various methods going beyond density functional theory (DFT), such as DFT+U, hybrid functionals, meta-GGAs, GW, and DFT-embedded dynamical mean field theory (eDMFT), have been developed to describe the electronic structure of correlated materials, but it is unclear how accurate these methods can be expected to be when applied to a given strongly correlated solid. It is thus of pressing interest to compare their accuracy as they apply to different categories of materials. Here we introduce a novel paradigm in which a chosen set of beyond-DFT methods is systematically and uniformly tested on a chosen class of materials. For a first application, we choose the target materials to be the binary transition metal oxides FeO, CoO, MnO, and NiO in their antiferromagnetic phase and present a head-to-head comparison of spectral properties as computed using the various methods. We also compare with available experimental angle-resolved photoemission spectroscopy (ARPES), inverse-photoemission spectroscopy, and with optical absorption. For the class of compounds studied here, we find that both B3LYP and eDMFT reproduce the experiments quite well, with eDMFT doing best, in particular when comparing with the ARPES data.

Highlights

Future technologies depend on new materials with tailored, enhanced, and/or novel functionalities
Showed before (Fig. 1) that, except for NiO, eDMFT peak positions in the Density of states (DOS) are in slightly better agreement with PES/IPES, Optical absorption we expect the spectral functions of eDMFT are likely a better prediction for angle-resolved inverse photoemission as well
It is tempting to speculate that the first conduction state in all four transition metal oxides (TMOs) is such a we present our results for the optical absorption, which measures the vertical transitions between the single-particle states, computed by B3LYP and eDMFT

Summary

INTRODUCTION

Future technologies depend on new materials with tailored, enhanced, and/or novel functionalities. While it is slightly underestimated by B3LYP, the agreement with the experimental used, multiple solutions are often found in the literature for FeO and CoO in DFT+U and mBJ methods.[7,13] GW0 on top of local density approximation (LDA) predicts both FeO and CoO to be metallic (not shown) Both B3LYP and eDMFT show a very good agreement with the PES/IPES (Fig. 1) for all four TMOs, except for FeO. As was the case for MnO, all four TMOs. we discuss spectral functions as computed both B3LYP and eDMFT predict the experimental PES/IPES spectra by these two methods, shown, which reproduce and go very well (Fig. 1b), with a slightly better match in B3LYP. Showed before (Fig. 1) that, except for NiO, eDMFT peak positions in the DOS are in slightly better agreement with PES/IPES, Optical absorption we expect the spectral functions of eDMFT are likely a better prediction for angle-resolved inverse photoemission as well. We notice the similar flat band in the and peaks do not align), seems superior in CoO, with an overall experimental APRES spectrum for CoO in the paramagnetic good match and a correct gap

DISCUSSION

METHODS