The thermal diffusion factor of the van der Waals binary mixture

The explicit dependence of the thermal diffusion factor with respect to composition and interaction parameters for the van der Waals binary mixture is obtained in the framework of the mean-field kinetic variational theory and in the scheme of Scott and van Konynenburg. Here, we present a numerical study where the global behavior of the thermal diffusion factor is described in terms of molecular masses, sizes, and interaction parameters, along the phase diagram of this model mixture. This numerical study allows us to understand what molecular parameters modify the sign of the thermal diffusion factor. In addition, a comparison is made between the thermal diffusion factor coming from the van der Waals mixture and from the hard-sphere mixture.