Abstract

First principles molecular dynamics has been used to investigate the structural, vibrational, and energetic properties of [Ca(H2O)(n)](2+) clusters with n=1-9, and the hydration shell of a calcium ion in a periodically repeated box with 54 water molecules. We find that, while stable highly symmetric Ca-water clusters can be formed with up to eight water molecules, the n=9 cluster dissociates into the last stable [Ca(H2O)8](2+) complex. In solution the first hydration shell around the Ca2+ ion contains six water molecules in an octahedral arrangement. The electronic structure of nearest neighbor hydration shell water molecules has been examined with a localized orbital analysis. The average dipole moments of hydration water molecules was found to be increased by about 0.4 Debye relative to that of pure water.