(180b) Molecular Dynamics Study On the Melting Point of Ionic Liquid [Emim]Br

How to get the melting points of ionic liquids below the room temperature is the major problem in the applications of ionic liquids. High costs in experiments, lack of precise descriptions of microstructures and complicated effects, all these make the experimental determination of melting points of ionic liquids difficult, however molecular dynamics simulations can complement to experimental investigation. In this work, molecular dynamics simulations are carried out to study the melting point of ionic liquids [emim]Br by the direct heating method, void-introduced method, sandwich method and NVE ensemble method, to find the most suitable method to predict the melting point by simulation. By analyzing the variations of the nonbonded energy, density, radial distribution function, diffusion coefficient and translational order parameter of [emim]Br with temperature, the results of the four methods are 548±8 K,370±6 K,373±4 K and 335±3 K, respectively, which is approximately 55.7%,5.1%,6.0% and -4.8% higher than the experimental value of 352 K. The advantages and disadvantages of each method and the mechanism of melting are also discussed.