MOLECULAR-DYNAMICS SIMULATIONS OF AQUEOUS IONIC CLUSTERS USING POLARIZABLE WATER

The solvation properties of a chlorine ion in small water clusters are investigated using state-of-the-art statistical mechanics. The simulations employ the polarizable water model developed recently by Dang [J. Chem. Phys. 97, 2659 (1992)]. The ion-water interaction potentials are defined such that the successive binding energies for the ionic clusters, and the solvation enthalpy, bulk vertical binding energy, and structural properties of the aqueous solution agree with the best available results obtained from experiments. Simulated vertical electron binding energies of the ionic clusters Cl-(H2O)n, (n = 1-6) are found to be in modest agreement with data from recent photoelectron spectroscopy experiments. Minimum energy configurations for the clusters as a function of ion polarizability are compared with the recent quantum chemical calculations of Combariza, Kestner, and Jortner [Chem. Phys. Lett. 203, 423 (1993)]. Equilibrium cluster configurations at 200 K are described in terms of surface and interior solvation states for the ion, and are found to be dependent on the magnitude of the Cl- polarizability assumed in the simulations.