Density functional theory study of the interaction of monomeric water with the Ag{111} surface

Ab initio density-functional theory has been used to investigate the adsorption of a single H₂O molecule on the Ag{111} surface. A series of geometry optimizations on a slab model has allowed us to identify a preferred energy minimum and several stationary points in the potential-energy surface of this system. The most stable adsorption position for water corresponds to the atop site, with the dipole moment of the molecule oriented nearly parallel to the surface. The electronic structure of several H₂O-Ag clusters has been compared to results obtained by the extended slab calculations. The agreement found for several properties (binding energy, tilt angle of the dipole moment of water, and interatomic distances) provides evidence for the local nature of the water-metal atop interaction. The covalent contribution to the weak H₂O-Ag bond is found to be an important one.