Gravar-mail: Comparative Hybrid Hartree-Fock-DFT Calculations of WO<sub>2</sub>-Terminated Cubic WO<sub>3</sub> as Well as SrTiO<sub>3</sub>, BaTiO<sub>3</sub>, PbTiO<sub>3</sub> and CaTiO<sub>3</sub> (001) Surfaces