Solvent effect for an effective attraction between like-charged macroions immersed in an electrolyte solution: The intensification mechanism of the effective attraction caused by the translational motion of solvent particles.

The effective interaction between macroanions immersed in an electrolyte solution was calculated using an integral equation theory of liquids to study the solvent granularity effect on the effective attraction mediated by cations. Explicit and implicit solvent models were examined. The effective attraction for the explicit solvent model was found to be stronger than that for the implicit solvent model. This solvent effect was remarkably enhanced only when the effective attraction between macroanions was strong; this means that the solvent effect is not a usual excluded volume effect. The intensification mechanism of the attraction by the solvent granularity is analyzed in the present study, and an indirect mechanism is proposed.