  In some binary fluids, mass transport is observed under a temperature
gradient. This phenomenon is called the Soret effect. In this study, we discuss
the influence of inter-particle interaction. We considered equimolar binary
Lennard-Jones fluids with a mass contrast, whereas the interaction was common
for all the particle pairs with various cut-off lengths. We performed molecular
dynamics simulations of such fluids under equilibrium to obtain the
cross-transport coefficients L1q between the fluxes of mass and heat. The
simulation revealed that this quantity strongly depends on the cut-off length.
Further, we decomposed the heat flux into kinetic and potential contributions
and calculated the cross-correlations between decomposed fluxes and the mass
flux. The result indicates that the potential contribution dominates L1q,
implying that the Soret coefficient is altered by the inter-particle
interaction.
