Inhomogeneity in Ethylammonium Nitrate-Acetonitrile Binary Mixtures: The Highest "low q Excess" Reported to Date

The binary mixtures of the ionic liquid ethylammonium nitrate with acetonitrile have been studied by means of wide- and small-angle X-ray scattering and via two different computational methods, namely, classical molecular dynamics and DFT. The recently debated odd feature in the extreme low q region of some ionic liquid-based binary mixtures is linked to density fluctuations within the system. We show how the "low q excess" is due to some nanoscopic objects which are formed at certain compositions. These structures have different density with respect to the surrounding, thus generating the feature observed. Our results also show how the local arrangement is directly linked to the long-range structure. Moreover, we found once again a similarity in the physicochemical behavior of ethylammonium nitrate and water.