(321be) Estimation of Critical Points from the Virial Equation of State

Mayer sampling refers to a collection of methods adapted from applications involving the calculation of free energies, and applied to the calculation of cluster integrals that appear in many theories of statistical mechanics. We have used Mayer sampling to determine virial coefficients (up to B6) for a Lennard Jones fluid, 2-center Lennard Jones plus point quadrupole, water, short square-well chains and TraPPE force-field alkanes. This paper describes our work to use the virial coefficients to calculate the critical point. While the virial equation of state fails at the critical point, in some cases it has been found to provide a useful approximation of the critical temperature. We examine the effect and relative importance of each successive term in the virial series on the predicted critical point for the systems listed above. By considering a wide range of fluids, we address the appropriateness of using a virial series approach to calculating the critical point.