Scaling Perspectives of Underscreening in Concentrated Electrolyte Solutions

TL;DR

This paper proposes a scaling model for underscreening in concentrated electrolyte solutions, explaining how the screening length increases with concentration due to hydrated ion clusters, supported by simulations and theoretical analysis.

Contribution

It introduces a novel scaling perspective and a cluster-based model to explain underscreening phenomena in high-concentration salt solutions.

Findings

Screening length increases with concentration above 1M.

Hydrated ion clusters with a single unpaired ion dominate the environment.

Scaling laws agree with experimental observations.

Abstract

We present a scaling view of underscreening observed in salt solutions in the range of concentrations greater than about 1M, in which the screening length increases with concentration. The system consists of hydrated clusters of positive and negative ions with a single unpaired ion as suggested by recent simulations. The environment of this ion is more hydrated than average which leads to a self-similar situation in which the size of this environment scales with the screening length. The prefactor involves the local dielectric constant and the cluster density. The scaling arguments as well as the cluster model lead to scaling of the screening length with the ion concentration, in agreement with observations.