First-principles study of KTaO3 under uniaxial strain

Perovskite oxides often undergo structural phase transitions due to phonons that become unstable under strain, where novel phenomena such as ferroelectricity or multiferroicity emerge. As a result, first-principles studies of perovskites under biaxial strain abound. In this study, we perform a first principles investigation of the phonon dispersions and phase diagram of the incipient ferroelectric KTaO3 under uniaxial strain. We find that ferroelectricity can be induced by compressive uniaxial strain, and that the strain axis is important in determining the critical strain for the emergence of polarization. These results provide insight on the intricate relation between vibrational modes and strain, and allows a comparison of uniaxial and biaxial strain boundary conditions.