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 simula tions employ the polarizable water model developed recently by Dang [J . Chem. Phys. 97, 2659 (1992)]. The ion-water interaction potentials a re defined such that the successive binding energies for the ionic clu sters, and the solvation enthalpy, bulk vertical binding energy, and s tructural properties of the aqueous solution agree with the best avail able results obtained from experiments. Simulated vertical electron bi nding energies of the ionic clusters Cl-(H2O)n, (n = 1-6) are found to be in modest agreement with data from recent photoelectron spectrosco py experiments. Minimum energy configurations for the clusters as a fu nction of ion polarizability are compared with the recent quantum chem ical calculations of Combariza, Kestner, and Jortner [Chem. Phys. Lett . 203, 423 (1993)]. Equilibrium cluster configurations at 200 K are de scribed in terms of surface and interior solvation states for the ion, and are found to be dependent on the magnitude of the Cl- polarizabil ity assumed in the simulations.