Comparative hybrid hartree-fock-dft calculations of wo2-terminated cubic wo3 as well as srtio3, batio3, pbtio3 and catio3 (001) surfaces

We performed, to the best of our knowledge, the world’s first first-principles calculations for the WO₂-terminated cubic WO₃ (001) surface and analyzed the systematic trends in the WO₃, SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ (001) surface ab initio calculations. According to our first principles calculations, all WO₂ or TiO₂-terminated WO₃, SrTiO₃, BaTiO₃, PbTiO₃ and CaZrO₃ (001) surface upper-layer atoms relax inwards towards the crystal bulk, while all second-layer atoms relax upwards. The only two exceptions are outward relaxations of first layer WO₂ and TiO₂-terminated WO₃ and PbTiO₃ (001) surface O atoms. The WO₂ or TiO₂-terminated WO₃, SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ (001) surface-band gaps at the Γ–Γ point are smaller than their respective bulk-band gaps. The Ti–O chemical bond populations in the SrTiO₃, BaTiO₃, PbTiO₃ and CaTiO₃ bulk are smaller than those near the TiO₂-terminated (001) surfaces. Conversely, the W–O chemical bond population in the WO₃ bulk is larger than near the WO₂-terminated WO₃ (001) surface.