Computational study of (111) epitaxially strained ferroelectric perovskites BaTiO3 and PbTiO3

The phase transition behavior of PbTiO3 and BaTiO3 under (111) epitaxial strain is investigated using density-functional theory calculations. From tensile strains of +0.015 to compressive strains of -0.015, PbTiO3 undergoes phase transitions from C2 through two Cm phases and then to R3m. The total polarization is found to be almost independent of strain. For the same range of strains BaTiO3 undergoes phase transitions from a single Cm phase, through R3m and then to R (3) over barm. In this case the application of compressive strain inhibits and then completely suppresses the polarization on transition to the nonpolar R (3) over barm phase.