Heat and matter transport in binary liquid mixtures

Abstract

Following some preliminary clarification of microscopic heat current definitions for mixtures, we describe nonequilibrium molecular dynamics algorithms for the evaluation of heat and matter transport coefficients in binary liquid mixtures. Simulations have been carried out for a dense fluid of Lennard-Jones atoms, approximating an equimolar argon-krypton mixture, at a thermodynamic state which has been studied in several previous equilibrium simulations. Our results suggest that the estimates of the mutual diffusion coefficient from these equilibrium simulations are \ensuremath{\sim}15% too high. Most importantly, we determine the cross-coupling coefficients which characterize the Soret and Dufour effects. These are obtained from two entirely independent sets of simulations and are found to be equal, in accordance with an Onsager reciprocal relation. When we run our algorithms with high external fields, we incidentally find evidence of demixing which is of interest in the general context of nonequilibrium phase transitions.