Adsorption of water on NaNO3(001) surface from first-principles calculations.

Density functional theory (DFT) calculations were applied to investigate the adsorption of water monomer, water clusters on NaNO(3)(001) surface. Single water molecule is more likely to locate on the bridge site with its H atom attracted by the O atom of nitrate ion and its O atom adjacent to Na(+). Mulliken population analysis shows that fewer electrons transfer from the Na atom of substrate to water molecule. A systematic study of water clusters adsorption at high coverages ranging from 0.5 monolayer (ML), 0.75 ML, 1 ML, 1.25 ML, and 1.5 ML on NaNO(3)(001) surface was also investigated, and the results indicate that for 1 ML water adsorption on NaNO(3)(001) surface, a water chain is formed among four water molecules through hydrogen bonds. Interestingly, the water molecules are linked through hydrogen bonds to form a 14-membered macrocyclic water ring for 1.5 ML adsorption on NaNO(3)(001) surface. Our estimated O-H symmetric stretching frequency (ν(O-H)) will have blueshift with decrease of water coverage, which is consistent with the tendency given by experiments.