Ion correlation-driven like-charge attraction in multivalent salt solutions

Nikhil R Agrawal; Ravtej Kaur; Carlo Carraro; Rui Wang

doi:10.1063/5.0181061

Ion correlation-driven like-charge attraction in multivalent salt solutions

J Chem Phys. 2023 Dec 28;159(24):244905. doi: 10.1063/5.0181061.

Authors

Nikhil R Agrawal¹, Ravtej Kaur¹, Carlo Carraro¹, Rui Wang^{1

2}

Affiliations

¹ Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA.
² Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

PMID: 38153151
DOI: 10.1063/5.0181061

Abstract

The electrostatic double layer force is key to determining the stability and self-assembly of charged colloids and many other soft matter systems. Fully understanding the attractive force between two like-charged surfaces remains a great challenge. Here, we apply the modified Gaussian renormalized fluctuation theory to study ion correlation-driven like-charge attraction in multivalent salt solutions. The effects of spatially varying ion correlations on the structure of overlapping double layers and their free energy are self-consistently accounted for. In the presence of multivalent salts, increasing surface charge or counterion valency leads to a short-range attraction. We demonstrate that although both overcharging and like-charge attraction are outcomes of ion correlation, there is no causal relationship between them. Our theory also captures the non-monotonic dependence of like-charge attraction on multivalent salt concentration. The reduction of attraction at high salt concentrations could be a contributing factor toward the reentrant stability of charged colloidal suspensions. Our theoretical predictions are consistent with the observations reported in experiments and simulations.