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 BO2-terminations 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.