Computer simulations of the restricted primitive model at very low temperature and density

TL;DR

This paper introduces a novel numerical method that significantly accelerates the simulation of the restricted primitive model (RPM) for ionic fluids at extremely low temperatures and densities, enabling equilibration in regimes previously inaccessible.

Contribution

The authors develop a new simulation technique that allows RPM to be equilibrated at very low concentrations and temperatures, overcoming traditional equilibration challenges.

Findings

Successfully equilibrated RPM at densities as low as 10^{-10}σ^{-3}

First simulation of RPM at such low concentrations

Method applicable to other aggregating systems

Abstract

The problem of successfully simulating ionic fluids at low temperature and low density states is well known in the simulation literature: using conventional methods, the system is not able to equilibrate rapidly due to the presence of strongly associated cation-anion pairs. In this manuscript we present a numerical method for speeding up computer simulations of the restricted primitive model (RPM) at low temperatures (around the critical temperature) and at very low densities (down to $10^{-10}\sigma^{-3}$, where $\sigma$ is the ion diameter). Experimentally, this regime corresponds to typical concentrations of electrolytes in nonaqueous solvents. As far as we are aware, this is the first time that the RPM has been equilibrated at such extremely low concentrations. More generally, this method could be used to equilibrate other systems that form aggregates at low concentrations.