Wetting in the binary Gaussian core model

Using a simple mean-field density functional approach we investigate the adsorption of a binary fluid mixture of repulsive Gaussian core particles at a repulsive planar wall. For certain choices of wall-fluid potential we find a first-order wetting transition, and the accompanying pre-wetting line, whereby the fluid phase rich in the larger species completely wets the interface between the wall and the fluid phase rich in the smaller species. We show that in the complete wetting regime the film thickness diverges as l similar to -l(0) ln(x - x(coex)), where (x - x(coex)) is the deviation in concentration x of the smaller species from the bulk binodal, for all the (short-ranged) wall potentials that we have considered but the amplitude l(0) depends on the precise details of these potentials.