Origin of the light green color and electronic ground state ofLaCrO3

Abstract

The electronic structure and optical properties of LaCrO3 have been calculated and the origin of the light green color of LaCrO3 has been identified. An optical gap of 1=3.4 eV was reproduced in agreement with experiment, which is a charge transfer gap. Another optical gap, 0=2.15 eV, which is not present in experiments has also been found and explains the light green color of this compound. The energy band gap between the top of the valence band and the bottom of the conduction band is =1.40 eV and has Mott character. Our calculated x-ray photoemission spectra XPS and x-ray absorption spectra at the oxygen K edge O-K XAS are in very good agreement with experiments. In contrast to previous reports, these results have been obtained using standard generalized gradient approximation calculations, while additional correlation effects for Cr 3d states due to an effective Hubbard U would result in a colorless LaCrO3 and a disagreement with XPS and XAS experiments. Thus, LaCrO3 should not be considered as highly correlated transition metal oxide, a conclusion also valid for many Cr3+ compounds.