Excess Entropy Scaling Explains the Enhanced Dynamics of the Ionic Liquid 1-ethyl-3-methylimidazolium Chloride in External Electric Fields

Abstract

In this study, we test scaling relationships between excess entropy and self-diffusion of the ionic liquid (IL) 1-ethyl-3-methylimidazolium chloride ([C₂C₁im][Cl]) across temperatures and varying external electric fields (EEFs). EEFs are observed to increase the dynamics of the IL by altering the structure of the liquid. This study assesses the validity of excess entropy scaling relationships for predicting self-diffusion coefficients of an IL across various temperatures and EEFs using molecular dynamics simulations. We compute the excess entropy of [C₂C₁im][Cl] to quantify EEF-induced structural changes and diffusion behavior. Results show that EEFs primarily affect anion-anion organization at short and medium length scales, while cation-cation ordering shifts only at long length scales. Additionally, counterion configurational ordering dominates excess entropy contributions over radial or translational organization. These findings establish excess entropy scaling as a robust tool for describing IL transport under EEFs, informing the design of solvents for sustainable separations under external stimuli.