(258d) Higher Order Virial Coefficients and Molecular Clustering of Polarizable Water Models

Mayer Sampling molecular simulation is a free energy perturbation method for calculating cluster integrals [1]. It has been used recently to determine higher order virial coefficients (up to B₆) for the Lennard-Jones fluid and various non-polarizable, pair-wise water models [1,2]. Here we employ the Mayer Sampling method to determine higher order virial coefficients for polarizable water. We have calculated up to B₄ for the polarizable point charge (PPC) model of Svishchev et al. [3] and the Gaussian charge polarizable model (GCPM) proposed by Chialvo and Cummings [4]. This work represents the first accounting of polarization in the Mayer Sampling method, and the first determination of B₄ for PPC water and B₃ and B₄ for GCPM water. Additionally, we use these virial coefficients to examine gas-phase molecular clustering in both water models under a range of sub- and super-critical conditions.

(1) Singh, J.K.; Kofke, D.A. Mayer Sampling: Calculation of cluster integrals using free-energy perturbation methods. Phys. Rev. Lett. 2004, 92, Art. No. 220601.

(2) Singh, J.K.; Benjamin, K.M.; Schultz, A.J.; Kofke, D.A. Higher order virial coefficients of water models. J. Phys. Chem. B. to be submitted.

(3) Svishchev, I.M.; Kusalik, P.G.; Wang, J.; Boyd, R.J. Polarizable point-charge model for water: Results under normal and extreme conditions. J. Chem. Phys. 1996, 105, 4742.

(4) Chialvo, A.A.; Cummings, P.T. Simple transferable intermolecular potential for the molecular simulation of water over wide ranges of state conditions. Fluid Phase Equil., 1998, 150, 73.