Phase stability and dielectric constant of ABO_3 perovskites from first principles

摘要

Using ab initio simulations we determine the stable phases of ABO_3 perovskites (A =Ca,Sr,Ba; fi=Ti,Zr,Hf) at T=0 K by calculating the free energy. For these structures we calculate the dielectric constant and the bandgap. It turns out that for tolerance factors far from 1, the stable phase is always Pnma. For SrZrO_3 and BaZrO_3 with tolerance factors close to 1, we predict that the high temperature cubic phase is broken to 14/mcm like in case of SrTiO_3 with a very small gain in free energy. The calculated dielectric constants are in agreement with the experimental values for the few cases known.