An investigation was made of the nature of the atomic relaxations, around O-vacancy defects in this ferro-electric perovskite, via first-principles pseudopotential total-energy calculations. A tail-to-tail polarization was detected in the atomic relaxations around O vacancies, and its stability was enhanced by charge trapping. It was noted that the O vacancies in Ti-O-Ti chains along the polarization axis were more favorable than those in Ti-O-Ti planes that were normal to the axis.

C.H.Park, D.J.Chadi: Physical Review B, 1998, 57[22], R13961-4