Homogenous mixing of ionic liquids: molecular dynamics simulationsElectronic supplementary information (ESI) available: Radial distribution function plots for cation-BF4, cation-PF6, H2-F (BF4), and H2-F (PF6), the spatial density map of anions around cations, normalized coordination number vs. mol fraction plots between H2-F (BF4), H2-F (PF6), and the partial structure factor between PF6-BF4 (for [C4mim][PF6] and [C4mim][BF4] mixture) along with coarse grained force field parameters. See DOI: 1

Binary mixtures of room temperature ionic liquids (IL) with a common cation were investigated using atomistic molecular dynamics (MD) simulations. Two different binary ILs, viz. , [C 4 mim][PF 6 ]-[C 4 mim][Cl] and [C 4 mim][PF 6 ]-[C 4 mim][BF 4 ], were studied with varying fractions of either anion. The coordination environment of an anion around the cation is altered in the presence of another type of anion. The extent of change is larger for anions with much different radii. Atomistic MD and coarse grain MD simulations do not show any evidence for the clustering of like anions at any concentration. The binary liquids are well mixed at the molecular level. Room temperature ionic liquids containing two different anions mix homogenously at the molecular level. The smaller anion preferentially forms hydrogen bonds with the most acidic proton of the imidazolium cation.