On the transition from surface to interior solvation in iodide–water clusters

A quantitative investigation of surface vs. interior solvation in iodide–water clusters was performed by evaluating the potentials of mean force and structural properties of I−(H2O)n clusters (n=32, 64) from Monte Carlo simulations with both non-polarizable and polarizable model potentials. Simulation results clearly indicate that the iodide ion tends to reside at the surface of a water cluster of size 32, whereas entropy and polarization effects make the interior solvation state more likely for a cluster size of 64. This is consistent with previous analyses of cluster experimental and model data, which suggest a transition from surface to bulk behavior around a cluster size of 60.