EMPIRICAL-MODELS FOR THE HYDRATION OF PROTONS

Two empirical models are considered for the hydrates H+ (H2O)n. In one, a rigid hydronium unit interacts with n - 1 water molecules, and in another, a single proton with an effective hard-core radius interacts with n waters. In each case, the polarizable representation of the water molecule developed by Kozack and Jordan is used. The two models are employed in a study of clusters with 1 less-than-or-equal-to n less-than-or-equal-to 7 and it is found that while both yield minimum-energy structures in good agreement with ab initio studies, the experimental hydration energies are much better accounted for within the proton model.