Virial Coefficients of Polarizable Water:  Applications to Thermodynamic Properties and Molecular Clustering

Abstract

We determine the second and third virial coefficients B2 and B3 for the Gaussian charge polarizable model (GCPM) as a function of temperature over the range 210−723 K. The overlap sampling implementation of Mayer sampling molecular simulation is applied to calculate the values, obtaining results to a precision that ranges from 0.1% for B2 to an average of 1% for B3. These calculated values compare very well with known values of B2 and B3 for real water and outperform both pairwise models and other polarizable models in describing experimental virial-coefficient data. We examine these coefficients in the context of the equation of state and molecular clustering. Comparisons are made to established molecular simulation data, quantum chemical calculations, and experimental data for real water. Under both saturated-vapor and supercritical conditions, the virial series up to B3 describes the equation of state quite well. The virial coefficients are used to characterize molecular clusters (dimers and trimers) in GCPM water under supercritical, saturated vapor, and atmospheric conditions between 210−673 K. The analysis shows that the extent of clustering in polarizable water is diminished relative to that from a pairwise water model.