PHOTOELECTRON-SPECTRA OF THE HYDRATED IODINE ANION FROM MOLECULAR-DYNAMICS SIMULATIONS

In this paper, we present the first calculations, based on molecular d ynamics techniques, of vertical electron binding energies for the ioni c clusters I- (H2O)n, (n=1-15). In these studies, we employ the polari zable water model developed recently by Dang [J. Chem. Phys. 97, 2659 (1992)]. We construct the ion-water potential so that the successive b inding energies for the ionic clusters, the hydration enthalpy, and th e structural properties of the aqueous ionic solution agree with the r esults obtained from experiments. The simulated vertical electron bind ing energies compare well with recent data from photoelectron spectros copy experiments by Markovich, Giniger, Levin, and Cheshnovsky [J. Che m. Phys. 95, 9416 (1991)]. Interestingly, we obtain coordination numbe rs of 4 to 5 for the ionic clusters, I- (H2O)n, for n greater-than-or- equal-to 6. This result is smaller than the coordination number, based on the energetic properties predicted by Markovich et al Possible rea sons for this discrepancy are discussed in the paper. Furthermore, our simulations place the iodine anion on the surface of the water cluste rs. This study demonstrates the usefulness of the molecular dynamics t echnique and provides a detailed picture of the ion solvation in clust ers.