Ionic Cloud Distribution close to a Charged Surface in the Presence of Salt

TL;DR

This paper introduces a formalism to predict ionic distributions near charged surfaces in salt solutions, covering various coupling regimes and salt concentrations, with explicit calculations for planar geometries.

Contribution

It provides a unified theoretical framework for ionic cloud distributions near macroions under diverse salt conditions and coupling strengths, including explicit planar case solutions.

Findings

Explicit ionic distribution functions near charged walls.

Identification of physical regimes via phase diagram.

Applicability to both mean field and strong coupling limits.

Abstract

Despite its importance, the understanding of ionic cloud distribution close to a charged macroion under physiological salt conditions has remained very limited especially for strongly coupled systems with, for instance, multivalent counterions. Here we present a formalism that predicts both counterion and coion distributions in the vicinity of a charged macroion for an arbitrary amount of added salt and in both limits of mean field and strong coupling. The distribution functions are calculated explicitly for ions next to an infinite planar charged wall. We present a schematic phase diagram identifying different physical regimes in terms of electrostatic coupling parameter and bulk salt concentration.