Comparative ab initio calculations of SrTiO3, BaTiO3, PbTiO3, and SrZrO3 (001) and (111) surfaces as well as oxygen vacancies

The paper presents and discusses the results of our performed ab initio calculations for perovskites SrTiO₃, BaTiO₃, PbTiO₃, and SrZrO₃ (001) and (111) surfaces by means of the hybrid B3PW or B3LYP description of exchange and correlation. According to our performed ab initio calculations for SrTiO₃, BaTiO₃, PbTiO₃, and SrZrO₃ (001) surfaces, in most cases, the upper layer atoms relax inwards, towards the bulk, and the second layer atoms relax upwards. The SrTiO₃, BaTiO₃, PbTiO₃, and SrZrO₃ (001) surface energies for AO and BO₂terminations are almost equal. Just opposite, our calculated surface energies for both AO₃ and B-terminated (111) surfaces are quite different. Our calculated SrTiO₃, BaTiO₃, PbTiO₃, and SrZrO₃ (111) surface energies always are considerably larger than the (001) surface energies. The SrTiO₃, BaTiO₃, PbTiO₃, and SrZrO₃ bulk Ti-O (Zr-O) chemical bond covalency increases near their BO₂-terminated (001) as well as AO₃-terminated (111) surfaces. We discussed systematic trends in SrTiO₃, BaTiO₃, PbTiO₃, and SrZrO₃ bulk and (001) surface F center ab initio calculations.