Effect of short and long range forces on the thermodynamic properties of water. A simple short range reference system

Three realistic potential models of water, the non-polarizable ST2 and TIP4 P models, and the polarizable TIP4P/P model, were used in computer simulati ons to study the effect of the range of intermolecular interactions on the thermodynamic properties of water. Following the results of recent studies, a short range system is constructed to the full pair potential u(1,2) in s uch a way that a perturbation expansion can be formulated in powers of the dipole-dipole interaction only. Computations of low density properties and comput er simulations performed for several densities on three subcritical and one supercritical isotherms show that the short range reference not onl y reproduces the structure but approximates also the internal energy and pr essure of water surprisingly well. Differences in the internal energy betwe en the full and short range water do not exceed 5% for all models used over the entire range of the thermodynamic conditions considered.