LDA calculations of the pressure induced structural changes and phase transitions in PbTiO3

Hydrostatic pressure induced structural and phase transformations in PbTiO3 were investigated by means of all-electron total energy local density full potential LMTO calculations for the entire structural parameter space of the ferroelectric state. The calculated equilibrium structural parameters, compressibilities and their pressure dependence are found to be in reasonable agreement with available experimental data. The zero-temperature tetragonal-cubic phase transition is estimated to occur at a pressure of 16.4 GPa. Results for the lattice constants reveal an anomalous pressure dependence of the spontaneous strain near a pressure of approximately 1.0 GPa. The a lattice constant is found to expand below approximately 1.0 GPa at the rate 1.4×10-3 angstroms(GPa)-1 and to decrease above approximately 1 GPa. Finally, the derivative of the spontaneous strain decreases drastically with pressure near approximately 1.0 GPa.