(708e) Evaluation of Virial Coefficients and Their Temperature Derivatives for Multibody Potential Models
AIChE Annual Meeting
2017
2017 Annual Meeting
Engineering Sciences and Fundamentals
Development of Intermolecular Potential Models
Thursday, November 2, 2017 - 1:34pm to 1:50pm
With improvements in simulation algorithms and computer speed, it is becoming increasingly viable to perform simulations using potentials that more accurately describe the true interactions between/among two, three, or more molecules. This includes polarizable models such as GCPM, and explicit pair and three-body potentials fit to ab initio potential surfaces. A crucial test of any model that purports to describe true intermolecular interactions is its ability to reproduce experimental virial-coefficient data, which rigorously characterize interactions of two, three, etc. molecules.
Wheatley recently introduced a very efficient recursive algorithm for evaluation of the integrand needed for virial coefficient calculations. Wheatleyâs derivation assumes a pairwise additive potential, but we show that it may be extended for application to multibody potentials, and moreover it provides a route for calculation of temperature derivatives. This allows calculation of high-order virial coefficients for such models. Coefficients determined this way can be compared to experimental data where available (which is typically no higher than the 3rd-order coefficient), thereby providing an assessment of the accuracy of the model. It can also be used to formulate equations of state that are fully predictive and accurate over much of the supercritical region, for both pure substances and mixtures; these models may also be used to compute critical properties. In this manner the usefulness of the accurate molecular model is greatly extended. We discuss these issues and demonstrate applications.