Studying the occupied and unoccupied electronic structure of LaCoO$_{3}$ by using DFT+embedded DMFT method with the calculated value of $\textit{U}$

TL;DR

This study compares DFT, DFT+U, and DFT+embedded DMFT methods to analyze LaCoO$_{3}$'s electronic structure, finding that the embedded DMFT approach with a specific U value best matches experimental data.

Contribution

It demonstrates that DFT+embedded DMFT with a calculated U value provides a more accurate description of LaCoO$_{3}$'s electronic states than DFT or DFT+U methods.

Findings

DFT fails to produce a proper energy gap.

DFT+U with the calculated U creates an inconsistent gap.

DFT+embedded DMFT accurately reproduces experimental spectra.

Abstract

In this work, we present a systematic study of the occupied and unoccupied electronic states of LaCoO$_{3}$ compound using DFT, DFT+$\textit{U}$ and DFT+embedded DMFT methods. The value of $\textit{U}$ used here is evaluated by using constrained DFT method and found to be $ \backsim $ 6.9 eV. It is found that DFT result has limitations with energy positions of PDOS peaks due to its inability of creating a hard gap although the DOS distribution appears to be fine with experimental attributes. The calculated value of $\textit{U}$ is not an appropriate value for carrying out DFT+$\textit{U}$ calculations as it has created an insulating gap of $ \backsim $ 1.8 eV with limitations in redistribution of DOS which is inconsistent with experimental spectral behaviour for the occupied states mainly. However, this value of $\textit{U}$ is found to be an appropriate one for DFT+embedded DMFT method which creates a gap of $\backsim $ 1.1 eV. The calculated PDOS of Co 3$\textit{d}$, La 5$\textit{d}$, La 4$\textit{f}$ and O 2$\textit{p}$ states are giving a remarkably good explanation for the occupied and unoccupied states of the experimental spectra in the energy range $\backsim $ -9.0 eV to $\backsim $ 12.0 eV.