Mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and acetonitrile: a molecular simulation

TL;DR

This study develops and validates a molecular simulation force field for mixtures of ionic liquids and acetonitrile, accurately predicting thermodynamic, structural, and transport properties across all compositions.

Contribution

It introduces a new force field approach that effectively models mixtures of ionic liquids and acetonitrile, validated against experimental data.

Findings

Scaled-charge model best reproduces experimental data

Force field accurately predicts all transport properties

Model validity is independent of mixture composition

Abstract

Recently, we introduced a new force field (FF) to simulate transport properties of imidazolium-based room-temperature ionic liquids (RTILs) using a solid physical background. In the present work, we apply this FF to derive thermodynamic, structure, and transport properties of the mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4], and acetonitrile (ACN) over the whole composition range. Three approaches to derive a force field are formulated based on different treatments of the ion-ion and ion-molecule Coulomb interactions using unit-charge, scaled-charge and floating-charge approaches. The simulation results are justified with the help of experimental data on specific density and shear viscosity for these mixtures. We find that a phenomenological account (particularly, simple scaled-charge model) of electronic polarization leads to the best-performing model. Remarkably, its validity does not depend on the molar fraction of [BMIM][BF4] in the mixture. The derived FF is so far the first molecular model which is able to simulate all transport properties of the mixtures, comprising RTIL and ACN, fully realistically.