ab initio Study of Strain-Induced Ferroelectricity in SrTiO3

Valley lines on total-energy surfaces for the zone-center distortions of free-standing and in-plane strained SrTiO3 are investigated with a newly developed first-principles structure optimization technique [Jpn. J. Appl. Phys. 43 (2004) 6785]. The results of numerical calculations confirmed that ferroelectricity is induced and the Curie temperature is increased by applying biaxial compressive or tensile strains. Along the distortion, strong nonlinear coupling between the soft- and hard-modes is demonstrated.