Charge distributions in water and ion–water clusters

We applied sequential atomic multipole fitting and the Gauss electric field flux theorem to calculate total molecular charge, charge distribution and charge transfer in a number of water, ion, and ion–water clusters. We have found that: (a) charge redistribution upon formation of ionic and of hydrogen bonds are similar and they are drastically different in covalent bonding; (b) polarization accounts for charge re-distribution upon formation of ionic or hydrogen bonds without invoking a charge transfer; (c) the `charge leakʹ from molecular cavities, encountered in the hydration theories, is usually compensated by the electron density of the surrounding water; (d) the flux theorem provides alternative means of defining atomic radii in molecules in solution or clusters.