Thermodynamics of Electrolytes on Anisotropic Lattices

TL;DR

This study uses Monte Carlo simulations to explore the phase behavior of ionic fluids on anisotropic lattices, revealing a consistent coexistence between disordered and ordered phases and providing tricritical parameters across anisotropies.

Contribution

It provides the first comprehensive simulation-based analysis of electrolyte phase behavior on anisotropic lattices, contrasting recent theoretical predictions.

Findings

Only coexistence between disordered and ordered phases was observed.

Tricritical parameters increase monotonically with anisotropy.

At high anisotropy, behavior approaches two-dimensional electrolyte characteristics.

Abstract

The phase behavior of ionic fluids on simple cubic and tetragonal (anisotropic) lattices has been studied by grand canonical Monte Carlo simulations. Systems with both the true lattice Coulombic potential and continuous-space $1/r$ electrostatic interactions have been investigated. At all degrees of anisotropy, only coexistence between a disordered low-density phase and an ordered high-density phase with the structure similar to ionic crystal was found, in contrast to recent theoretical predictions. Tricritical parameters were determined to be monotonously increasing functions of anisotropy parameters which is consistent with theoretical calculations based on the Debye-H\"uckel approach. At large anisotropies a two-dimensional-like behavior is observed, from which we estimated the dimensionless tricritical temperature and density for the two-dimensional square lattice electrolyte to be $T^*_{tri}=0.14$ and $\rho^*_{tri} = 0.70$.