A state-of-the-art theoretical method for estimating ultrasonic velocity in ionic liquid mixtures: An extension of McAllister's interaction model

•McAllister’s Interaction Model(MAIM) is extended, for the first time, from four-body to nine-body interactions among binary mixtures of ionic liquids and water.•It has also been tested to predict the ultrasonic velocity in eight binary mixtures at different compositions and temperatures.•Extended MAIM for nine-body interactions has shown excellent agreement with the experimental value of ultrasonic velocity for all the mixtures.•Extended Huckel theory has been employed to compute the charge distribution to identify active sites for interaction.