Switching of a substitutional-iron/oxygen-vacancy defect complex in ferroelectric PbTiO3 from first principles

A combination of first-principles calculations and atomistic simulations was used to study the energy barriers for reorientation of the Fe-Ti'-V-O(center dot center dot) defect complex in tetragonal ferroelectric PbTiO3 via migration of the oxygen vacancy next to the iron substitutional. It was found that the barrier for reorientation strongly depends on the position of the migrating oxygen vacancy with respect to the iron atom and the surrounding spontaneous ferroelectric polarization. The obtained results indicate that the defect complex can play a different role in the switching of the spontaneous ferroelectric polarization in PbTiO3 by 90 degrees or 180 degrees.