First-principles Calculations of Structural Changes Induced by Oxygen Vacancies in Tetragonal Phase BaTiO3

Structural changes induced by oxygen vacancies in tetragonal phase BaTiO3 are studied with first principles calculations within density functional theory. In our calculations, the incorporation of oxygen vacancies greatly decreases c/a ratio of the tetragonal phase BaTiO3, and a phase transition from tetragonal to cubic phase occurs when the incorporation of the oxygen vacancies reaches about 4%. Our results also shows that the generation of the oxygen vacancies slightly increases the volume of BaTiO3, and the increases are typically less than 0.5% even in heavily reduced conditions.