Electronic and oxygen migration properties of monoclinic La ₂GeO_5-δ

We investigated the electronic and oxygen migration properties of monoclinic lanthanum germanate La₂GeO_5-δ by first-principles calculation based on the density functional theory. Based on analysis of the electronic density of states, it was confirmed that an oxygen-deficient crystal with a composition of La₂GeO_4:75 retains the insulating property with a band gap of 3.519 eV as well as the perfect crystal with a gap of 4.044 eV. The contribution of each atomic orbital to electronic densities of states was evaluated from the partial densities of states and partial charge distribution of a defect-originated state. By using climbing image nudged elastic band method, we obtained the activation barrier for oxygen hopping between nearest-neighbor sites and this value was comparable with experimental one.