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arXiv · 2306.10137

Ion correlation driven like-charge attraction in multivalent salt solutions

Nikhil R. Agrawal·Ravtej Kaur·Carlo Carraro·Rui Wang
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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 towards the reentrant stability of charged colloidal suspensions. Our theoretical predictions are consistent with the observations reported in experiments and simulations.

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Nikhil R. Agrawal, Ravtej Kaur, Carlo Carraro, Rui Wang. 2023-06-16. Ion correlation driven like-charge attraction in multivalent salt solutions. https://doi.org/10.1063/5.0181061

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