First-Principles Based Design of Low Tolerance Factor Perovskites

We study the structural and vibrational properties of perovskite materials over a wide range of tolerance factors using first-principles calculations. We demonstrate how low tolerance factor materials that have been artificially constrained to the Pnma structure show ferroelectric instabilities. Our results are correlated with physical descriptors, such as ionic radii and electronegativity. The rules obtained from our first-principles analysis will provide useful guidance for design of the new ferroelectric materials.