The missing term in effective pair potentials

Effective pair potentials used for simulations of polar liquids include the average effects of polarization. Such potentials are generally adjusted to produce the experimental heat of vaporization. It has not been recognized before that the self-energy term inherent in any polarizable model should be included in effective pair potentials as well. Inclusion of the self-energy correction with a consequent reparametrization of the SPC (simple point charge) model of water yields an improvement of the effective pair potential for water, as exemplified by density, radial distribution functions, and diffusion constant.