Physisorption of water on salt surfaces

Results of ab initio calculations of water adsorption on clean NaCl(1 0 0) surfaces show that favorable adsorption geometries critically depend on the competition of water–surface and water–water interactions. At the most favorable adsorption site, the oxygen is near the cation with hydrogens forming hydrogen bonds with nearest anions. For monolayer adsorption, the water–water interaction is decisive for the clustering of water molecules. We also discuss a hexagonal (2×4) bilayer ice-like structure. Molecular-dynamics simulations give new insight into the dynamic stability of different adsorption geometries. Finally, some complementary results for KCl are given, in which case the interaction of oxygen and cation is weaker.