Effective interactions and volume energies in charge-stabilized colloidal suspensions

Abstract

Charge-stabilized colloidal suspensions can be conveniently described by\nformally reducing the macroion-microion mixture to an equivalent one-component\nsystem of pseudo-particles. Within this scheme, the utility of a linear\nresponse approximation for deriving effective interparticle interactions has\nbeen demonstrated [M. J. Grimson and M. Silbert, Mol. Phys. 74, 397 (1991)].\nHere the response approach is extended to suspensions of finite-sized macroions\nand used to derive explicit expressions for (1) an effective electrostatic pair\ninteraction between pseudo-macroions and (2) an associated volume energy that\ncontributes to the total free energy. The derivation recovers precisely the\nform of the DLVO screened-Coulomb effective pair interaction for spherical\nmacroions and makes manifest the important influence of the volume energy on\nthermodynamic properties of deionized suspensions. Excluded volume corrections\nare implicitly incorporated through a natural modification of the inverse\nscreening length. By including nonlinear response of counterions to macroions,\nthe theory may be generalized to systematically investigate effective many-body\ninteractions.\n