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

Abstract

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.

Integral equation study of effective attraction between like-charged particles mediated by cations: Comparison between IPY2 and HNC closures

“…Because the calculation cost for "Model A", that was mentioned above, was too expensive, the solvent hard spheres and the macroanions were removed from it. The results calculated using the HNC closure showed that the solvent hard spheres intensify the effective attraction between like-charged particles [40,41]. However, the explicit solvent model was not required, and the implicit solvent model also showed the effective attraction and the reentrant behavior in our studies [40,41].…”

“…[44], the IPY2-OZ theory gave reasonable correlation functions for highly associating ionic systems such as the 2:2 electrolytes, whereas for monovalent ionic systems the HNC-OZ theory was known to be reasonable [41,45,46]. The model adopted in this study was a mixture of monovalent and multivalent ions, which is an intermediate system between the above-mentioned references [41,[44][45][46]. Moreover, this study has dealt with the effective attraction between like-charged particles, which was not considered in the previous studies [41,[44][45][46].…”

“…Therefore, we adopt the different types of anion pairs in Models A and B. This difference in the stablest conformation depends on the size ratio and the depletion effect caused by the solvent particles [40,41]. As the size ratio becomes more significant and the depletion effect becomes stronger, the contact dimer becomes stabler.…”

“…The results calculated using the HNC closure showed that the solvent hard spheres intensify the effective attraction between like-charged particles [40,41]. However, the explicit solvent model was not required, and the implicit solvent model also showed the effective attraction and the reentrant behavior in our studies [40,41]. Therefore, this model was selected to reduce the computational costs.…”

“…( 6). It has been used to study electrolyte solutions [26][27][28][29][30][31][32][33][34][35][37][38][39][40][41]. The equation is as follows:…”