Strain-induced structural phase transition and the rotation of polarization in BaTiO3 films

Based on the density-functional theory, the structural transitions manipulated by the biaxial strains are investigated in BaTiO3 film using the first-principles calculations. It is found that when the compressive strain is increased continuously in the single domain BaTiO3 films, a phase transition occurs from r phase to c phase, on the contrary, when the tensile strain is increased, there will be a successive phase transition from t phase to r phase, then to aa phase. All structural phase transitions are second-order, and r phase always integrates into other phases after phase transitions. Furthermore, it is found that the spontaneous polarization vector P → can rotates continuously in the 1 ¯ 10 plane, and fails to mutate during phase transition. At last, we also explain this strain induced polarization rotation in detail according to the orbital hybridization between Ti-O ions.