An exploration of mixing rules for pair-potentials

Modern thermochemical codes produce EOS for high pressure fluid mixtures (such as detonation products) via modelling intermolecular interactions through pair potentials. While statistical mechanics theories allow for the creation of an EOS from a pair potential for a pure fluid, their extension to mixtures is nontrivial. Therefore, a mixing rule is needed to predict the EOS of an arbitrary mixture of the constituents from the EOS of the pure species.



Prior work (Subramanian, Leiding, Belfield, Proceedings of the 17th International Detonation Symposium, 2024) that compared and contrasted a pair of mixing rules demonstrated that the simpler ideal mixing rule performed well due to a cancellation of errors type phenomenon. The prior work also suggested a new mixing rule, the performance of which we have now examined, as well as a number of possible future research paths. In particular, we have examined phenomena related to the combining rule used to generate the parameters used for interactions between molecules of different species. Previous work used the "standard" Lorentz-Berthelot rules, which while not being explicitly featured in the ideal mixing approach appeared to be implicitly captured.

This abstract has been designated LA-UR-25-20489