Molecular Simulation of Ionic Liquid Nanodroplets in Electric Fields

We report results of large scale molecular dynamics simulations of nanodroplets of the ionic liquid 1-ethyl-3-methylimidaziolium bis(trifluoromethylsulfonyl)imide in the presence of an electric field. The simulations are designed to mimic the behavior of ionic liquids in electrospray thrusters. We observe the formation of individual ions, as well as neutral and non-neutral clusters. The critical field strength where ion emission is observed is computed as a function of droplet size. We find that field strengths of about 1 V/nm are required to observe ion emission in large droplets, in good agreement with experiment. As droplet size decreases, the critical field strength required to observe ion emission increases. Other structural and dynamic properties of the ionic liquid are computed and compared to those obtained when no field is present.