Effect of dispersion on the structure and dynamics of the ionic liquid 1-ethyl-3-methylimidazolium thiocyanate.

We present a comprehensive density functional study, using the Perdew-Burke-Ernzerhof (PBE) functional, to elucidate the effect of including or neglecting the dispersion correction on the structure and dynamics of the ionic liquid 1-ethyl-3-methylimidazolium thiocyanate. We have investigated the structure of the liquid phase and observed that specific interactions between the anions and cations of the ionic liquid were not accurately represented if the dispersion was neglected. The dynamics of the system is more accurately described if the dispersion correction is taken into account and its omission also leads to an incorrect representation of the hydrogen-bonding dynamics. Finally, the power spectrum is predicted and in good agreement with experimental results. Thus, we conclude that it is possible to represent the structure and dynamics of systems containing ionic liquids accurately using ab initio molecular dynamics and a correction for dispersion.