First-principles study of elastic properties in perovskite PbTiO3

The first-principles calculations of elastic properties in cubic and tetragonal PbTiO3 were performed. Bulk modulus and elastic constants were determined from a density-function theory method within the local density approximation. The clamped-ion and internal-strain parts of elastic constants were computed and found that clamped-ion parts are dominant. The theoretical bulk modulus, Bcubic = 229 GPa and Btetragonal = 61 GPa, agree well with the single crystal experimental data. As a by-product of elasticity calculation, the equilibrium tetragonal-to-cubic phase transition pressure were derived from the enthalpy difference, Pc = 10.1 GPa, consist with the experimental values.