Ab initio study of the oxygen vacancy in SrTiO3

The electrical properties of SrTiO3 are strongly dependent on the oxygen vacancy concentration. We have studied the atomic and electronic properties of a single oxygen vacancy using a local spin density approximation-planewave pseudopotential method. The total energies, relaxed geometries, valence charge and spin densities, and densities of electron states are calculated for different charge states of the vacancy. The doubly positively charged state is found to be the most stable. With some charge states, a spin-polarized defect state is observed. Furthermore, we have evaluated the formation energy of the vacancy in the O-O --> V-O + 1/2O(2) process.