Integral equations for the pair structure: An efficient method for studying the potential of mean force in strongly confined colloids

The domain of validity of a recently proposed method for studying inhomogeneous colloidal mixtures is discussed. In this method, bridge functions derived from Rosenfeld's hard-sphere bridge functional are used in the reference hypernetted chain closure of the Ornstein-Zernike equations, the inhomogeneity being treated by following the technique of Henderson, Abraham, and Barker. To better assess the accuracy of this method, we present new theoretical and simulation results for the wall- macroparticle potential of mean force in demanding conditions that combine the effect of strong confinement and of very short-range attractions between the colloidal particles. We show that this method satisfactorily predicts an efficient role of very short-range solvation forces, in a pseudobinary mixture confined in a slit pore that can accommodate only one big macroparticle in the direction normal to the walls.