Vacancy-assisted ferroelectric domain growth in BaTiO₃ under an applied electric field: A molecular dynamics study

BaTiO₃ is a well-known piezoelectric material, which is widely used in various devices. In general, the ferroelectric state of BaTiO₃ is composed of polarized domains. The growth of these domains due to an applied electric field or stress is related to the piezoelectric performance. We investigated the effects of various point defects, monovacancies {V_Ba, V_Ti, V_O}, and first- and second-neighbor divacancies {V_Ba–V_O, V_Ti–V_O} on polarized domain growth in BaTiO₃ under an applied electric field by molecular dynamics simulations using the core–shell inter-atomic potential. We found that (i) the first-neighbor divacancy V_Ba–V_O is the most effective in assisting the domain growth under an applied electric field (i.e., a smaller coercive electric field) in an asymmetrical manner with respect to the electric field direction. This is mainly due to the creation of an electric field around V_Ba–V_O by significant Ti shifts toward V_Ba with the assistance of V_O. (ii) Domain growth proceeds in a $1+2$ dimensional manner. The domain growth velocity in the direction of the applied electric field is approximately two orders of magnitude higher than that in the perpendicular direction. (iii) Increasing the density of the divacancy V_Ba–V_O further lowers the coercive electric field when the applied electric field is parallel to the divacancy dipoles. The present results will be essential for designing the type, orientation, and density of defects to modify the coercive electric field of BaTiO₃ in defect engineering.