Structure factor lineshape model gives approximate nanoscale size of polar aggregates in the ionic liquid N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide

Abstract

A Lorentzian lineshape model is developed and tested for the charge alternation peak in X-ray structure factors calculated from MD simulations for N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide. Applying the model to published, experimental X-ray scattering data reproduces calculated cation–cation and anion–anion distances within 6% and implies that half of ionic aggregates are larger than 12.7 Å.