Theory of cross-diffusivity in a binary fluid mixture

Abstract

A microscopic approach for the cross-diffusivity in a binary fluid mixture has been developed using the theoretical frameworks of density functional theory (DFT) as well as mode coupling theory (MCT). In MCT, we have identified a particular mode selection which leads to an expression for the cross-diffusivity identical to that obtained from the DFT. An alternative choice based on analogous physical considerations though leads to a different expression, on numerical evaluation shows that the calculated results are close to the predictions from DFT. Both the theories are applied to a Lennard-Jones fluid mixture and the calculated cross-diffusivities are found to be in good agreement with the available computer simulation results.