First-principles study of CaTiO3 oxygen-vacancies (0Â 0Â 1) surface

The structural and electronic properties of fully relaxed CaTiO3 oxygen-vacancies (0 0 1) surface with CaO and TiO2 terminations are investigated by first-principles plane waves ultrasoft pseudopotential method based on local density approximation. The present results show that the direction and the magnitudes of the atomic relaxations for oxygen-vacancies surface are different from that of the perfect surface. Compared with the TiO2-terminated oxygen-vacancy surface, the CaO-terminated oxygen-vacancy surface are likely to be observed in oxygen environment conditions. Much different from the perfect surface, the oxygen-vacancy surface becomes metallic caused by some states in the conduction band are lowered and pulled down in the band-gap region.