Comparative Hybrid Hartree-Fock-DFT Calculations of ReO3, SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001) Surfaces

We carried out comparative first principles calculations for the ReO₂-terminated ReO₃ as well as TiO₂-terminated SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ (001) surfaces. As follows from our first principles calculations, systematic trend for the ReO₂-terminated ReO₃ as well as for TiO₂-terminated SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ (001) surfaces is inward relaxation of all upper layer and outward relaxation of all second layer atoms. The only two exceptions from this systematic trend is outward relaxation of the first layer O atom on the TiO₂-terminated PbTiO₃ (001) surface as well as inward relaxation of the ReO₂-terminated ReO₃ (001) surface second layer O atom. Our calculated band gaps at the Γ-Γ point point for the ReO₂-terminated ReO₃ as well as TiO₂-terminated SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ (001) surfaces in all cases are decreased regarding to the respective bulk values. Just opposite to the TiO₂-terminated SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ (001) surfaces, where the Ti-O chemical bond population are larger than in the bulk, near the ReO₂-terminated ReO₃ (001) surface, the Re-O chemical bond population is reduced in comparison to the bulk value.