Density functional calculation of the geometric and electronic structure of a(1×1)and a(1×3)supported gold system:Au∕TiO3∕Mo(112)

We report a density functional calculation which optimizes a structure of supported Au on titania $\mathrm{Au}∕\mathrm{Ti}{\mathrm{O}}_{3}∕\mathrm{Mo}(112)$. Our computations include two different surface configurations $(1\ifmmode\times\else\texttimes\fi{}1)$ and $(1\ifmmode\times\else\texttimes\fi{}3)$. The results of our study detail the geometric and the electronic structure of these systems. The $(1\ifmmode\times\else\texttimes\fi{}1)$ structure has a ${\mathrm{Au}}^{\ensuremath{\delta}\ensuremath{-}}$ monolayer for its top surface. When the Au coverage is increased, the partial second layer of Au (1/3 ML) causes the titania layer to reconstruct, providing a surface made up of three forms of Au (${\mathrm{Au}}^{\ensuremath{\delta}\ensuremath{-}}$, ${\mathrm{Au}}^{0}$, and ${\mathrm{Au}}^{\ensuremath{\delta}+}$). We have added a vibrational component to our study which permits a possible experimental check on our proposed structures. We calculated the frequencies for a CO molecule when chemisorbed and optimized on these ${\mathrm{Au}}^{\ensuremath{\delta}\ensuremath{-}}$, ${\mathrm{Au}}^{0}$, and ${\mathrm{Au}}^{\ensuremath{\delta}+}∕{\mathrm{Au}}^{0}$ bridge sites. The ${\mathrm{Au}}^{\ensuremath{\delta}+}∕{\mathrm{Au}}^{0}$ bridge site has the largest charge transfer with the adsorbing CO and the CO vibrational frequency is redshifted by $321\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ $(40\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$. We observe that the $2{\ensuremath{\pi}}^{*}$ antibonding level of the CO is above the Fermi level and the electronic density of states shows that the electronic levels reach continuously down passed the Fermi level.