Earliest Ionic Liquid Simulations

In 2001, Hanke, Price and Lynden-BelP were the first to conduct an atomistic simulation of compovmds that can be called ionic liquids under our definition. They used molecular dynamics to model the crystalline state of 1,3-dimethylimidazolium chloride ([Cimim][Cl]), 1,3-dimethylimidazolium hexafluorophosphate ([CimimllPFg]), l-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), and l-ethyl-3-methylimidazolium hexafluorophosphate ([C2 mimJlPFg]). They also modeled the liquid state of [Cimim][Cl] and [Cimim] [PFg], both of which are relatively high melting substances. Because of this (and the need to speed dynamics and thus limit computation times), the liquid simulations were carried out at temperatures between 400 and 500 K. The form of the potential function they used was 

Morrow and Maginn also carried out a molecular dynamics study of [C4mim][PF6], using an explicit-atom and fully flexible model with a force field having the following functional form  

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The repulsion of fully occupied orbitals in model systems received attention in the earliest application of quantum mechanical methods. From those studies an exponential representation of the energy-distance curve was obtained. This functional form has been used extensively in the simulation of both solids and molecular systems. Also derived from early quantum mechanical results were potentials using inverse power repulsive forms (see, e.g.. Refs. 49 and 50). Such potentials have also been employed with success in the simulation of liquids, molecular solids, and ionic systems. 

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