Fast estimation of ion-pairing for screening electrolytes: A cluster can approximate a bulk liquid

TL;DR

This paper presents a fast, cluster-based computational model to estimate ion-pairing in electrolytes, aiding the screening of new electrolyte materials with high efficiency and accuracy.

Contribution

Introduction of a novel cluster model and CLIPS tool for rapid ion-pair potential-of-mean-force estimation in electrolyte solutions.

Findings

Cluster model accurately predicts ion-pairing tendencies.

CLIPS tool enables efficient screening of electrolyte systems.

Model incorporates explicit solvent layers for realistic estimates.

Abstract

The propensity for ion-pairing can often dictate the thermodynamic and kinetic properties of electrolyte solutions. Fast and accurate estimates of ion-pairing can thus be extremely valuable for supplementing design and screening efforts for novel electrolytes. Here, we introduce an efficient cluster model to estimate the local ion-pair potential-of-mean-force (PMF) between ionic solutes in electrolytes. The model incorporates an ion-pair and a few layers of explicit solvent in a gas-phase cluster and leverages an enhanced sampling approach to achieve high efficiency and accuracy. We employ harmonic restraints to prevent solvent escape from the cluster and restrict sampling of large inter ion distances. We develop a Cluster Ion-Pair Sampling (CLIPS) tool that implements our cluster model and demonstrate its potential utility for screening simple and poly-electrolyte systems.