Attractive forces in sterically stabilized colloidal suspensions: from the effective potential to the phase diagram

The potential of mean force for macroparticles at infinite dilution is computed for several models of solvent-solvent and solvent-macroparticle interactions by using the reference hypernetted chain (RHNC) integral equations with Rosenfeld's density functional theory bridge functions. The phase diagram of the associated effective fluid is obtained from the RHNC free energy for the fluid branch and the perturbation theory for the solid one. The computation of the effective potential and of the fluid branch is tested by comparison with Monte Carlo simulation. The important modifications with respect to the pure hard spheres that were previously reported are confirmed. The possibility of inverting the relative stability of the fluid-fluid and the fluid-solid transitions by appropriate combination of the interaction parameters is shown. The importance of a fine description of the interactions is illustrated in the example of the role of the range of the solvent-solvent interaction potential.