EFFECTIVE POTENTIALS FOR LIQUID WATER USING POLARIZABLE AND NONPOLARIZABLE MODELS

Two three-site potentials for use in liquid water simulations are cons tructed using effective interactions. The rigid molecule has interacti on centers located at atomic sites coinciding with the gas-phase monom er geometry. One potential uses solely pairwise additive potential fun ctions whereas the other includes polarization contributions. These fu nctions and parameters are adjusted to give simulated liquid propertie s at room temperature that resemble the experimental values for struct ure, energy, and pressure. The models presented correspond to a reduce d effective representation of liquid water interactions and are labele d RER(pair) and RER(pol). Thus, the local structure of the liquid is r eproduced based on the pair correlation functions for atom pairs. Anal ysis of dynamical properties gives a diffusion coefficient of 2.4 x 10 (-5) and 2.8 X 10(-5) cm(2)/s for the nonpolarizable and polarizable m odel, respectively, results which can be compared with an experimental value of 2.4 x 10(-5) cm(2)/s determined by Krynicki et al. [Discuss. Faraday Sec. 1978, 66]. Reorientational relaxation times are also in general agreement with the available experimental data, with the polar izable model exhibiting somewhat faster overall dynamics than the nonp olarizable potential. The temperature dependence of the models was als o investigated in the liquid state between 250 and 350 K. The proposed models are computationally efficient and represent a viable alternati ve to other simple pairwise and polarizable three-center liquid water potentials.