Origin of the light green color and electronic ground state of LaCrO3

The electronic structure and optical properties of LaCrO(3) have been calculated and the origin of the light green color of LaCrO(3) has been identified. An optical gap of Delta(1)=3.4 eV was reproduced in agreement with experiment, which is a charge transfer gap. Another optical gap, Delta(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 Delta=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 LaCrO(3) and a disagreement with XPS and XAS experiments. Thus, LaCrO(3) should not be considered as highly correlated transition metal oxide, a conclusion also valid for many Cr(3+) compounds.