Temperature-pressure phase diagram and ferroelectric properties of BaTiO3 single crystal based on a modified Landau potential

A modified eighth-order Landau potential was proposed for the BaTiO3 single crystal by taking account into the quantum mechanical effects at low temperature. While all existing thermodynamic potentials for BaTiO3 fail to accurately describe the pressure dependence of ferroelectric transition temperatures, the temperature and hydrostatic pressure phase diagram constructed using the modified potential shows excellent agreement with experimental measurements by Ishidate, Abe, Takahashi, and Mori [Phys. Rev. Lett. 78, 2397 (1997)]. On the basis of the new proposed Landau potential, we calculated the dielectric coefficients, spontaneous polarizations, temperature-electric field phase diagram, and piezoelectric coefficients, all in good agreement well with existing experimental data.