Compositional and physical changes on perovskite crystal surfaces

The surface composition of BaTiO₃, SrTiO₃, and CaTiO₃ perovskite (100) surface is determined by shell-model calculations. The TiO₂-terminated surface is energetically favorable for BaTiO₃ and SrTiO₃, which is consistent with experimental observations on SrTiO₃. On the other hand, the CaO-terminated surface is preferred for CaTiO₃ where Ca²⁺ is the smallest 2+ cation in these titanates. Ions on (100) surface rumple and induce surface dipoles. The surface ferroelectric polarization stabilizes the surface and changes its sign as the surface composition changes from TiO₂ to CaO. This phenomenon is expected to affect the stability and properties of epitaxial films on perovskite substrates.