Effect of external static electric fields on the dynamic heterogeneity of ionic liquids.

Ionic liquids (ILs) exhibit behavior analogous to supercooled liquids at room or even higher temperatures. ILs usually work under an externally applied static electric field (E). In this work, molecular dynamics simulations were performed with 1-ethyl-3-methyl-imidazolium tetrafluorborate ([EMI+][BF4-]) under E, with the aim of discovering the influence of E on the dynamic heterogeneity of ILs. ILs show more homogeneous dynamics with increasing E, as indicated by non-Gaussian parameters and dynamic susceptibility. The dynamic heterogeneity is greater in the E direction than that in the perpendicular directions under the same E. Despite the dynamic heterogeneity, only a small decoupling between diffusion and relaxation is observed under E.