Intermolecular Potential-Based Equations of State from Molecular Simulation and Second Virial Coefficient Properties.

Abstract

The importance of both the Boyle temperature ( TB) and temperature maximum ( Tmax) for the ability of intermolecular potential-based equations of state to accurately predict second virial coefficient ( B) behavior was examined. The TB, Tmax, and B vs T behavior of several Lennard-Jones equations of state, developed from molecular simulation data, were compared with exact theoretical values. The analysis spanned low ( T ≤ TB), mid ( TB < T ≤ Tmax), and high ( T ≫ Tmax) temperatures. The value of TB was accurately predicted by most equations of state studied, whereas most failed to adequately predict Tmax. The ability to accurately predict both TB and Tmax appears to be correlated with the accurate prediction of B values for the entire range of temperatures. This provides a useful criterion to improve future potential-based equations of state. The Mecke et al. and Thol et al. Lennard-Jones equations of state yielded the most accurate results. In some cases, a many-fold improvement in accuracy was observed compared with alternative equations of state. The exact B data were also used to obtain accurate polynomial relationships covering different ranges of temperatures.