Dynamics of proton recombination with NO3- anion in water clusters

Recombination events of a proton with NO3- at (H2O)(8) clusters are studied by molecular dynamics, using on-the-fly'' reliable ab initio MP2 potentials. The main findings are: (1) the lifetime of the ions is less than 1.2 picoseconds; (2) the recombination step invariably involves H3O+, not H5O2+; and (3) an essentially unique transition-state structure of H3O+/NO3- for recombination is found in all cases. Proton migration involves both H3O+ and H5O2+ species: Grotthuss and other mechanisms contribute.