In this work we employed large-scale atomistic simulations to study structural and dynamic correlations in bulk ionic liquids. Specifically we focused on understanding of  two phenomena: 1) Inspired by several experimental data that reported three distinct peaks in neutron scattering structure factor with the lowest peak at Q=0.3 inverse Angstroms, we have set up large-scale simulations of bulk ionic liquids (C8mimTFSI and C6mimTFSI) using polarizable force field to investigate the origin and the mechanisms of dynamic relaxations contributing to this peak. The length and time scales associated with this peak are related to dynamic and structural relaxations of nanoscale domains formed by segregation of ionic and alkyl tail domains. 2) In other large-scale simulations we attempt to address the apparent long range screening length that has been observed in several recent experiments on bulk ionic liquids and concentrated electrolytes. While conventional Debye theory predicts a screening length on the order of couple Angstroms, recent AFM experiments with bulk ionic liquids indicate the presence of long-range forces implying a relatively large (several nanometers) screening length in bulk ionic liquids. To investigate this issue we have conducted simulations of a 50nm ionic liquid film between two charged electrodes and investigated the decay of various density and charge profiles as well as electrostatic field as a function of separation from the surface. Indeed our simulations indicate the presence of two screening regimes: a very sharp decay near the electrode surface (within 1-1.5nm) and a long-range decay (up to 5-6nm) from the surface.

Mesoscale structural and dynamic correlations in ionic liquids sampled by atomistic molecular dynamics simulations

255th National Meeting (2018)

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