Complex structure of ionic liquids. molecular dynamics studies with different cation-anion combinations

This article shows that the diverse structure and morphology of different ionic liquids can be interpreted using structure factor and radial distribution data. These two functions can be obtained using molecular dynamics (MD) simulation techniques. The lowest-q peaks of the structure factor spectra (prepeaks) can be assigned to characteristic separations between strands of the ionic liquid polar network that are mediated by nonpolar regions. On the other hand, the second lowest q-peaks reflect the medium-range ordering of the polar network itself. The systematic comparison between different groups of ionic liquids allows us to rationalize the relative amplitude and position of those peaks with the underlying structure of the ionic liquid and interpret such an outcome in terms of the relative size and nature of the corresponding ions.