Dynamic microscopic structures and dielectric response in the cubic-to-tetragonal phase transition for BaTiO3 studied by first-principles molecular dynamics simulation

摘要

The dynamic structures of the cubic and tetragonal phase in BaTiO3 and itsdielectric response above the cubic-to-tetragonal phase transition temperature(Tp) are studied by first-principles molecular dynamics (MD) simulation. It'sshown that the phase transition is due to the condensation of one of thetransverse correlations. Calculation of the phonon properties for both thecubic and tetragonal phase shows a saturation of the soft mode frequency near60 cm-1 near Tp and advocates its order-disorder nature. Our first-principlescalculation leads directly to a two modes feature of the dielectric functionabove Tp [Phys. Rev. B 28, 6097 (1983)], which well explains the long timecontroversies between experiments and theories.