Electronic structures and optical properties of monoclinic ZrO2 studied by first-principles local density approximation + U approach

The electronic structures and optical properties of the monoclinic ZrO 2 (m-ZrO 2 ) are investigated by means of first-principles local density approximation (LDA) + U approach. Without on-site Coulomb interactions, the band gap of m-ZrO 2 is 3.60 eV, much lower than the experimental value (5.8 eV). By introducing the Coulomb interactions of 4d orbitals on Zr atom ( U d ) and of 2p orbitals on O atom ( U p ), we can reproduce the experimental value of the band gap. The calculated dielectric function of m-ZrO 2 exhibits a small shoulder at the edge of the band gap in its imaginary part, while in the tetragonal ZrO 2 and cubic ZrO 2 it is absent, which is consistent with the experimental observations. The origin of the shoulder is attributed to the difference of electronic structures near the edge of the valence and conduction bands.