Ionic Size Effects on the Poisson-Boltzmann Theory

TL;DR

This paper introduces a modified Poisson-Boltzmann theory that accounts for ionic size effects, demonstrating high accuracy in predicting ionic distributions around charged particles, especially for large, low-concentration ions.

Contribution

The paper develops a simple, size-corrected Poisson-Boltzmann model validated against simulations and DFT, enhancing understanding of ionic distributions with finite ion sizes.

Findings

Good agreement with Monte Carlo simulations and DFT results.

Effective for high ionic radii and low concentrations.

Applicable to colloid and nanoparticle systems.

Abstract

In this paper we develop a simple theory to study the effects of ionic size on ionic distributions around a charged spherical particle. We include a correction to the regular Poisson-Boltzmann equation in order to take into account the size of ions in a mean-field regime. The results are compared with Monte Carlo simulations and a Density Functional Theory based on the Fundamental Measure approach and a second-order bulk expansion which accounts for electrostatic correlations. The agreement is very good even for multivalent ions. Our results show that the theory can be applied with very good accuracy in the description of ions with high effective ionic radii and low concentration, interacting with a colloid or nanoparticle in an electrolyte solution.