SOLVATION OF AMMONIUM ION - A MOLECULAR-DYNAMICS SIMULATION WITH NONADDITIVE POTENTIALS

Detailed solvation properties of an ammonium ion in polarizable water as a function of the number of water molecules are studied. Extensive molecular dynamics simulations are carried out to compute successive b inding enthalpies of the ionic clusters, solvation enthalpies, and str uctural properties of aqueous ionic solutions. The results of these si mulations indicate that water molecules in the first hydration shell a re tetrahedrally coordinated to the ammonium ion. The distribution of the static orientation of water dipole moments is calculated and found to be rather broad when compared to corresponding results obtained fo r simulations that use spherical cations.