Viscosity calculation of 1‑ethyl‑3‑methyl‑imidazolium chloride ionic liquids based on three-body potential hydrogen bond model

In this study, we have developed an all-atom force field with three-body hydrogen bond model for 1‑ethyl‑3‑methyl‑imidazolium chloride ([Emim][Cl]), predicted the experimental dynamic viscosity successfully and calculated the relationship between dynamic properties and ion pair (IP) structures relaxation time. The partial atom charges and parameters of Lennard-Jones and hydrogen bond model are derived from ab initio molecular dynamic (AIMD) simulations. The strategy is that charges are fitted by AIMD structures and parameters are adjusted to make structure consistent between molecular dynamic (MD) and AIMD. The dynamic viscosities were calculated by Green-Kubo (GK) relation and were in excellent agreement with experiments results. Structure of ionic liquids was studied by using several distribution functions and IP time response was calculated. The calculated IP lifetime was found in linear correlation with viscosity and self-dynamic coefficient.