EFFECTIVE POTENTIALS FOR LIQUID WATER USING POLARIZABLE AND NONPOLARIZABLE MODELS

Two three-site potentials for use in liquid water simulations are constructed using effective interactions. The rigid molecule has interaction centers located at atomic sites coinciding with the gas-phase monomer geometry. One potential uses solely pairwise additive potential functions whereas the other includes polarization contributions. These functions and parameters are adjusted to give simulated liquid properties at room temperature that resemble the experimental values for structure, energy, and pressure. The models presented correspond to a reduced effective representation of liquid water interactions and are labeled RER(pair) and RER(pol). Thus, the local structure of the liquid is reproduced based on the pair correlation functions for atom pairs. Analysis 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 model, 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 polarizable model exhibiting somewhat faster overall dynamics than the nonpolarizable potential. The temperature dependence of the models was also investigated in the liquid state between 250 and 350 K. The proposed models are computationally efficient and represent a viable alternative to other simple pairwise and polarizable three-center liquid water potentials.