Self-consistent field model for strong electrostatic correlations and inhomogeneous dielectric media

TL;DR

This paper introduces a self-consistent electrostatic model that accounts for strong ionic correlations and variable dielectric media, improving predictions of ionic distributions and interfacial phenomena beyond traditional mean-field theories.

Contribution

The authors develop a novel continuum electrostatic model incorporating space-dependent dielectric permittivity and ion size effects within a self-consistent field framework.

Findings

Model accurately predicts ionic distributions around macroions.

Captures charge inversion phenomena at high correlation regimes.

Shows significant effects of dielectric variability on double layer structure.

Abstract

Electrostatic correlations and variable permittivity of electrolytes are essential for exploring many chemical and physical properties of interfaces in aqueous solutions. We propose a continuum electrostatic model for the treatment of these effects in the framework of the self-consistent field theory. The model incorporates a space-or field-dependent dielectric permittivity and an excluded ion-size effect for the correlation energy. This results in a self-energy modified Poisson-Nernst-Planck or Poisson-Boltzmann equation together with state equations for the self energy and the dielectric function. We show that the ionic size is of significant importance in predicting a finite self energy for an ion in an inhomogeneous medium. Asymptotic approximation is proposed for the solution of a generalized Debye-Huckel equation, which has been shown to capture the ionic correlation and dielectric self energy. Through simulating ionic distribution surrounding a macroion, the modified self-consistent field model is shown to agree with particle-based Monte Carlo simulations. Numerical results for symmetric and asymmetric electrolytes demonstrate that the model is able to predict the charge inversion at high correlation regime in the presence of multivalent interfacial ions which is beyond the mean-field theory, and also show strong effect to double layer structure due to the space- or field-dependent dielectric permittivity.