A polarizable, four-point-charge model of water with size variation

The proposed model is classical, polarizable and can change its size responding to the impact of the surroundings. We introduce a qualitative theory which simultaneously changes polarization, repulsion and size. Larger electric fields in condensed phases pull the molecules closer and induce larger polarization than in gas phase. However, this causes exponential increase in repulsion as a result of overlapping electron clouds. To decrease the impact of this repulsion the electron cloud contracts slightly, which decrease its polarization. Since the size of the molecule is determined by the extension of its electron cloud, there will be a subtle equilibrium determined by the actual strength of the polarization force, the repulsion and the size of the molecule. Using the principles above, we developed a model and carried out numerical calculations. The properties of the dimer practically reproduce the experimental values. The estimates of the energy, the density and the structure of liquid water and hexagonal ice are also excellent. (C) 2009 Elsevier B.V. All rights reserved.