Structure and dynamics of Cl−(H2O)20 clusters: The effect of the polarizability and the charge of the ion

Abstract

The effect of the polarizability and the sign of the ionic charge were studied in Cl−(H2O)20clusters using molecular dynamicscomputer simulation technique. From our simulations we concluded that the reduction in the ionic polarizability did not significantly change the structure and dynamics of the Cl−(H2O)20cluster, but the inversion of the sign of the ionic charge produced a large effect. The energetic considerations helped us to understand why Cl− is located on the surface of the cluster. By being on the surface the anion permits the creation of the hydrogen bonded network between water molecules and that lowers the total energy of the cluster. Simulations with the inverted sign of the ionic charge correspond to that with a hypothetical ‘‘Cl+ ’’ ion which is similar in size and polarizability to a Cs+ ion. The dynamical structures and the quenched structures of Cl+(H2O)20clusters are compared with the idealized structure of the Cs+(H2O)20cluster proposed recently [A. Selinger and A. W. Castleman, Jr., J. Phys. Chem. 9 5, 8442 (1991)].