Ion pairing in model electrolytes: A study via three particle correlation functions

TL;DR

This paper introduces a three-particle correlation function approach to study ion pairing in electrolytes, showing good agreement with simulations and revealing ion pair formation under various conditions.

Contribution

It presents a novel three-particle extension of integral equations for electrolyte analysis, improving accuracy over traditional methods.

Findings

Good agreement with molecular dynamics simulations.

Supports formation of ion pairs and complexes.

Effective at low salt concentrations and high ionic valence.

Abstract

A novel integral equations approach is applied for studying ion pairing in the restricted primitive model (RPM) electrolyte, i. e., the three point extension (TPE) to the Ornstein-Zernike integral equations. In the TPE approach, the three-particle correlation functions $g^{[3]}({\bf r}_{1},{\bf r}_{2},{\bf r}_{3})$ are obtained. The TPE results are compared to molecular dynamics (MD) simulations and other theories. Good agreement between TPE and MD is observed for a wide range of parameters, particularly where standard integral equations theories fail, i. e., low salt concentration and high ionic valence. Our results support the formation of ion pairs and aligned ion complexes.