Lattice Models of Ionic Systems with Charge Asymmetry

TL;DR

This paper investigates the thermodynamics of charge-asymmetric lattice ionic systems using Debye-Hückel theory, analyzing cluster formation and solvation effects for various charge asymmetries, and compares results with simulations.

Contribution

It provides explicit analytic and numerical calculations of ionic lattice gases with charge asymmetry, incorporating cluster formation and solvation effects, extending Debye-Hückel theory.

Findings

Critical point shifts to lower temperatures with increased charge asymmetry

Results align with Monte Carlo simulations for continuum ionic fluids

Debye-Hückel theory effectively predicts trends in charge-asymmetric systems

Abstract

The thermodynamics of a charge-asymmetric lattice gas of positive ions carrying charge $q$ and negative ions with charge $-zq$ is investigated using Debye-H\"uckel theory. Explicit analytic and numerical calculations, which take into account the formation of neutral and charged clusters and cluster solvation by the residual ions, are performed for $z=2$, 3 and 4. As charge asymmetry increases, the predicted critical point shifts to lower temperatures and higher densities. This trend agrees well with the results from recent Monte Carlo simulations for continuum charge-asymmetric hard-sphere ionic fluids and with the corresponding predictions from continuum Debye-H\"uckel theory.