Lattice Model of an Ionic Liquid at an Electrified Interface

TL;DR

This study compares lattice Monte Carlo simulations and modified Poisson-Boltzmann theory for ionic liquids at electrified interfaces, revealing limitations of the theory and proposing a relation to connect lattice and continuum models.

Contribution

It introduces a lattice Coulomb gas model for ionic liquids and proposes a convolution relation linking lattice and continuum density profiles.

Findings

Modified Poisson-Boltzmann theory fails to capture double layer structure.

Lattice Monte Carlo simulations qualitatively match continuum double layer features.

A convolution relation approximately relates lattice and continuum ionic density profiles.

Abstract

We study ionic liquids interacting with electrified interfaces. The ionic fluid is modeled as a Coulomb lattice gas. We compare the ionic density profiles calculated using a popular modified Poisson-Boltzmann equation with the explicit Monte Carlo simulations. The modified Poisson-Boltzmann theory fails to capture the structural features of the double layer and is also unable to correctly predict the ionic density at the electrified interface. The lattice Monte Carlo simulations qualitatively capture the coarse-grained structure of the double layer in the continuum. We propose a convolution relation that semiquantitatively relates the ionic density profiles of a continuum ionic liquid and its lattice counterpart near an electrified interface.