Microstructure and intermolecular interactions of [Bmim][PF6]+Water+ Alcohol Systems: A molecular dynamics simulation study

Abstract

Studying the microstructure and intermolecular interactions of ionic liquid (IL) systems is of great importance. In this work, molecular dynamics (MD) simulations were performed on 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6])+water+ethanol and [Bmim][PF6]+water+isopropanol ternary systems. Radial distribution functions were calculated, and the interaction energies between ion pairs and mixed solvents of different compositions were decomposed into Coulombic interaction energies and Lennard-Jones (LJ) potentials. The microstructure and intermolecular interactions of the ternary systems were studied based on the results, and the phase behaviors of the systems were discussed. The results show that water tends to interact with the anion and polar part of the cation, while alcohols prefer to interact with the anion and nonpolar part of the cation. The Coulombic interaction dominates over the anion-solvent interaction, while the LJ interaction dominates over the cation-solvent interaction. The association state of the ion pair has a small effect on the LJ interaction, but a significant effect on the Coulombic interaction.