Energetic stability and photocatalytic activity of SrTiO3 nanowires: ab initio simulations

Abstract

First principles periodic calculations based on the density functional theory within the localized atomic orbital approach (DFT-LCAO) using the hybrid exchange–correlation potential PBE0 have been performed in order to simulate the structural and electronic properties of both stoichiometric and non-stoichiometric [001]-oriented four-faceted SrTiO₃ (STO) nanowires (NW) of cubic structure. Their diameters have been varied from 0.3 up to 2.4 nm with a corresponding consequent change of NW cross-section from 2 × 2 to 5 × 5 extension of the lattice constant in bulk. Energetic stability of STO NW (both stoichiometric and non-stoichiometric) has been found to increase with the decrease of their formation energies together with the increase of NW diameter. The electronic structure calculations have shown that the width of the band gap changes in STO NWs of different structural types as compared to that in bulk being consequently reduced with the growth of NW diameter although the character of such a decrease depends on the morphology of the nanowire. Analysis of these changes shows that stoichiometric and non-stoichiometric TiO₂-terminated strontium titanate nanowires can be quite promising candidates for further applications in photocatalytic processes under solar irradiation whereas SrO-terminated NWs are rather not suitable for this purpose.