A polarizable multistate empirical valence bond model for proton transport in aqueous solution

A multistate empirical valence bond model for proton transport in water, which explicitly includes solvent polarization, is presented. Polarization is included for each valence-bond state via induced point dipoles, and the model is parametrized to be used with an effective path integral derived potential surface, so as to include quantum effects of the transferring proton. The new model is shown to reproduce ab initio geometries and energetics for small protonated clusters. It is also shown that the new model gives a diffusion constant for the excess proton in water, which is in good agreement with experiment, and that the qualitative features of ab initio path integral simulations [D. Marx, M. E. Tuckerman, J. Hutter, and M. Parrinello, Nature (London) 397, 601 (1999)] are well reproduced.