Structure and dynamics of liquid water on rutile TiO₂(110)

Water on TiO₂(110) is the most widely studied water-oxide interface, yet questions about water dissociation and hydrogen bonding are controversial. Here we report density-functional theory simulations which show that water does not dissociate at the coverages examined. The aqueous film is layered, with slow moving molecules in the contact layer and fast moving molecules in a second layer, revealing strongly inhomogeneous dynamics of the interfacial water. Hydrogen bonding between the first and second layers is observed as is the exchange of water molecules. These results help to resolve a number of controversies pertaining to the molecular scale behavior of water on TiO₂ and provide insight in to the structure and dynamics of water-solid interfaces by, e.g., demonstrating that water dynamics can vary on the Angström length scale and that the presence of second layer water molecules can cause those in the first layer to reorient.