Macroion correlation effects in electrostatic screening and thermodynamics of highly charged colloids

TL;DR

This paper investigates macroion correlation effects on the thermodynamics of highly charged colloids, introducing an extended mean-field model that accounts for correlations, leading to more accurate predictions aligned with simulations and experiments.

Contribution

It proposes a simple extension to the renormalized jellium model to include macroion correlations in mean-field theory for colloidal suspensions.

Findings

Macroion correlations weaken screening effects.

Reduced effective macroion charge and osmotic pressure.

Model predictions agree with simulations and experiments.

Abstract

We study macroion correlation effects on the thermodynamics of highly charged colloidal suspensions using a mean-field theory and primitive model computer simulations. We suggest a simple way to include the macroion correlations into the mean-field theory as an extension of the renormalized jellium model of Trizac and Levin [Phys. Rev. E {\bf 69}, 031403 (2004)]. The effective screening parameters extracted from our mean-field approach are then used in a one-component model with macroions interacting via Yukawa-like potential to predict macroion distributions. We find that inclusion of macroion correlations leads to a weaker screening and hence smaller effective macroion charge and lower osmotic pressure of the colloidal dispersion as compared to other mean-field models. This result is supported by a comparison to primitive model simulations and experiments for charged macroions in the low-salt regime, where the macroion correlations are expected to be significant.