The double-layer of penetrable ions: an alternative route to charge reversal

TL;DR

This paper introduces a new mean-field mechanism for charge reversal in a system of penetrable ions near a charged wall, modeled through a modified Poisson-Boltzmann equation, validated by Monte Carlo simulations.

Contribution

It proposes a novel charge reversal mechanism in penetrable ionic systems using a mean-field approach, avoiding non-electrostatic forces.

Findings

Charge reversal occurs in the weak-coupling regime.

The system can be accurately described by a modified Poisson-Boltzmann equation.

Monte Carlo simulations confirm the theoretical predictions.

Abstract

We investigate a double-layer of penetrable ions near a charged wall. We find a new mechanism for charge reversal that occurs in the weak-coupling regime and, accordingly, the system is suitable for the mean-field analysis. The penetrability is achieved by smearing-out the ionic charge inside a sphere, so there is no need to introduce non-electrostatic forces and the system in the low coupling limit can be described by a modified version of the Poisson-Boltzmann equation. The predictions of the theory are compared with the Monte Carlo simulations.