HYDRATION OF CATIONS - H-BOND SHORTENING AS AN ELECTROSTATIC EFFECT

Ab initio calculations have been undertaken to explain the experimental observation of the shortened distance between the water molecules of the first and second hydration shells around cations in aqueous electrolyte solutions. Considering the simplest model consisting of a water dimer and a point-like positive charge, we found that the effect can be attributed to the shortening of the individual hydrogen bonds under the influence of the Coulombic field of the cation, and there is no need to assume any cooperative effect arising from a set of water molecules.