Cell volume effect on the ferroelectric stability of perovskite oxides pbtio₃ and batio₃ from first principle calculation

Electronic structure of ferroelectric PbTiO₃ and BaTiO₃ is calculated by the full potential linearized augmented plane wave method. The total energy as a function of the displacement of Ti-cation is obtained for PbTiO₃ and BaTiO₃ at different cell volumes. At experimental cell volume, Ti-displacement lowers the total energy and the ferroelectricity is stable. When the cell volume is reduced to 90%, total energy is increased with Ti-displacement and ferroelectricity will disappear. The cell volume effect is also confirmed by comparison of the density of states of Ti and O at different cell volumes.