First-principles calculation of defect energetics in cubic-BaTiO3 and a comparison with SrTiO3

The structural relaxation and formation energies of intrinsic vacancies in cubic-BaTiO3 were studied by using a first-principles planewave-based pseudopotential calculation. The calculated defect formation energies and the atomic relaxations were compared with previously reported data for SrTiO3 [Tanaka T, Matsunaga K, Ikuhara Y, Yamamoto T. Phys Rev B 2003;68:205213]. It was found that the formation energies of the partial Schottky species, V-Ti(2-) + V-O(2+) and V-Ba(2-) + V-O(2+), are the lowest in the oxidized condition. In contrast, as the oxygen chemical potential decreased, namely the reduced condition, the O vacancy becomes dominant in cubic-BaTiO3. Concerning the atomic relaxation, it was found that BaTiO3 and SrTiO3 show a difference in magnitude. It was also found that the overall vacancy formation energy in BaTiO3 is higher than that in SrTiO3. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.