Influence of intermolecular hydrogen bonding on water dissociation at the MgO(001) surface

The adsorption of water on the MgO(001) surface is studied by using density-functional theory calculations within the generalized gradient approximation. Our calculations show that coupled three and four water molecules are partly dissociated, indicating that the intermolecular hydrogen bonding plays an important role in water dissociation on MgO(001). Especially, four water molecules are found to be significantly stabilized due to the increase in the number of the intermolecular hydrogen bonds. This hydrogen-bonding unit can explain experimental observations of the $c(4\mathrm{}\times 2)$ phase and its transition to the $p(3\mathrm{}\times 2)$ phase composed of three water molecules.