Molecular Based Modeling of Polarizable Water Via Calculation of Cluster Integrals Based On Wertheim's Association Theory

Since associating fluids are governed by the short-ranged and strongly directional interaction between particles, the virial equation of state (VEOS) fails to predict the accurate thermodynamic behavior of associating fluids. As one possible way to substitute VEOS, Wertheim’s multi-density formalism for associating fluid systems is suggested in our work. In Wertheim’s formalism, the molecular level detail is maintained like VEOS, while the strong directional association between particles is taken into account explicitly. In previous work, we have verified the effectiveness of the Wertheim equation of state (WEOS) for one-, two-, and four-site models based on Wertheim theory compared to the VEOS. In current work, we examine WEOS for a Gaussian charge polarizable model (GCPM) of water developed by Paricaud et al. Wertheim’s three-site model, extended for application to multi-body potentials, is considered to describe the thermodynamic behavior of GCPM water. We compare the pressure for GCPM water as determined from various truncated WEOS to values from VEOS and from Monte Carlo simulation in the NPT ensemble. The cluster integrals contained in VEOS and WEOS are evaluated by Mayer Sampling Monte Carlo (MSMC) simulation. The thermodynamic properties of GCPM water obtained from Wertheim’s multi-density formalism are converging more to NPT simulation results compared to the conventional virial formalism.