On the molecular basis of water hydrolysis. A detailed ab initio study

A refined study of the water hydrolysis is made at the HF-MP2 level, with f ull counterpoise correction and many-body analysis. The O-H bond dissociati on occurring during water hydrolysis was studied in small water aggregates, from the trimer to hexamer, using fully optimized structures at the HF-MP2 level. The breaking of the O-H bond in these clusters is a complex reactio n. It is found that the H-bond coordination pattern for each monomer influe nces its role during the reaction. From a detailed analysis of molecular pr operties those roles can be clearly identified. The results obtained show t hat at least two water molecules should act as promoters of the hydrolysis reaction while the molecules intervening in the concerted double proton tra nsfer can be distinguished in the reactants structure by its large three-bo dy nonadditive interaction. Only one final structure, where the ions act as triple accepters and triple donors of H-bonds, becomes stable. The role of ion hydration in lowering the barrier for the hydrolysis reaction in these clusters is also discussed.