2009 Volume 50 Issue 5 Pages 977-983
The structural relaxations and the formation energies of intrinsic defects in cubic and orthorhombic CaTiO3 were investigated by a first principles projector-augmented wave method. It was found that cations and oxygen vacancies in both phases cause extra levels near the valence band maximum and the conduction band minimum, respectively, and the Ti-vacancy induced level in orthorhombic CaTiO3 is closer to the valence band maximum than that in cubic CaTiO3. Among the neutral defect species, including neutral isolated vacancy, partial Schottky, and full Schottky, it was found that the VCa2−+VO2+ and VO0 are the most preferable defect species for orthorhombic CaTiO3 under reduction and oxidization conditions, respectively, whereas the VCa2−+VO2+ partial Schottky is always stable in any atmosphere in cubic CaTiO3. As compared to cubic CaTiO3, it was found that orthorhombic CaTiO3 shows higher defect formation energies.