Journal of Chemical Physics, Vol.105, No.9, 3700-3714, 1996
Ion Solvation in Model Polar Clusters
We have studied solvation of an ion in model polar clusters of Stockmayer (Lennard-Jones + point dipole) particles to test previous theories of cluster ion solvation, and to elucidate trends that may serve as a point of departure for analysis of more complex systems. We find that the pure solvent cluster is not isotropic, but has a well-defined pattern of orientational order which is converted to another distinct pattern by the ion. The extent to which the cluster is reordered depends upon the relative magnitude of ionic strength and solvent polarity. In many instances the two forms of order coexist with solvent shells far from the ion behaving as they did before inclusion of the ion, which shells close to the ion are reordered in a manner that best solvates the ion. The location of the ion in the cluster depends on relative ionic strength as well. The location changes from the surface to the center of the cluster in a gradual manner as the relative ionic strength increases. Qualitative agreement with dielectric continuum theory is found for large clusters. Deviations from dielectric continuum theory are found for small clusters, as expected, and compared to a previous theoretical prediction of those deviations.
Keywords:MOLECULAR-DYNAMICS SIMULATIONS;PERIODIC BOUNDARY-CONDITIONS;MEAN SPHERICAL MODEL;WATER CLUSTERS;PHOTOELECTRON-SPECTROSCOPY;LIQUID-DROPS;ELECTROSTATIC SYSTEMS;CL-(H2O)N CLUSTERS;IODINE ANION;HARD-SPHERES