First-principles study of bulk and surface oxygen vacancies in SrTiO3 crystalV. E. Alexandrov, E. A. Kotomin, J. Maier and R. A. EvarestovEur. Phys. J. B, 72 1 (2009) 53-57DOI: https://doi.org/10.1140/epjb/e2009-00339-4