Ab-initio Study of Interactions of Gold Atoms with Hydroxylated MgO(001) Surfaces

By employing ab-initio electronic structure calculations based on the density functional theory, we investigated the adsorption, diffusion, bonding, and electronic properties associated with the enhanced bonding of Au on hydroxylated MgO(001) surfaces. The calculations in this study show that the binding of Au on hydroxylated MgO(001) is substantially enhanced by an ionic-like interaction as compared to the case of Au on regular MgO(001). Indeed, the adsorption of Au on hydroxylated MgO surfaces is stronger than that of Au and OH on MgO(001). AuOH complexes are formed on MgO(001) surfaces via the fast surface diffusion of OH and Au. It is found that the AuOH structure is very stable against not only dissociation (i.e., it is very difficult for it to decompose back into OH and Au) but also surface diffusion (i.e., it has low surface mobility). More detailed electronic structure analysis of the charge distribution of AuOH on MgO(001) reveals that the enhanced ionic-like bonding is achieved via the polarization variation in Au induced by both ionic OH and MgO surface atoms.