Single Vacancies and Vacancy Pairs in Tetragonal BaTiO3: A First Principles Study

The formation energies of single vacancies and vacancy pairs in the tetragonal BaTiO3 were studied using first principles computational method. The results show that under reduction conductions, oxygen vacancies have the lowest formation energy among single vacancies. For vacancy pairs, the formation energies of the Ba-O pair are lower than that of Ti-O under most thermodynamical conditions. Calculation of the polarization for system containing Ba-O vacancy pairs shows that depending on the direction of the electric dipole of the pair, the polarization is either enhanced or decreased, which may be related to the imprint behavior of ferroelectric materials.