Theory of the cubic-tetragonal phase transition in PbTiO_3

摘要

The phase transition in PbTiO_3 is discussed quantitatively from the microscopic free energy based upon the mean field approximation, where the Ti ions shift is considered as the order parameter in the lattice having the spontaneous deformation. From our calculation of the microscopic free energy, the ionic shift of the Ti ion and the coefficient of the expanded free energy, we concluded that the transition temperature and the order of cubic-tetragonal transition are well explained by this model.