Pressure-Induced Anomalous Phase Transitions and Colossal Enhancements of Piezoelectricity in Ground-State BaTiO₃

Rhombohedral BaTiO₃ under hydrostatic pressure is investigated by first principles calculations. Our results show that just like tetragonal perovskites, as pressure increases, this material first becomes para-electric at low pressures, then transfers to another ferroelectric phase at much higher pressures. We also find a giant enhancement of piezoelectricity near the phase-transition regions, due to large atomic displacements along different directions in response to the applied pressures.