Velocity field and velocity autocorrelation function in ionic liquids

摘要

A simple theory for the velocity autocorrelation function of twohyphen;component ionic liquids is developed with the use of a microscopic velocity field and a modehyphen;coupling method. Our expression for the velocity autocorrelation function consists of contributions from coupling to both masshyphen; and chargehyphen;current excitations, each with longitudinal and transverse components. The coupling strength to chargehyphen;current excitations is shown to be proportional to the mass ratio of the two ionic species. That is, e.g., cationic motion, the larger the mass ratiomminus;1/m1is, the stronger the coupling becomes wheremminus;1andm1denote masses of an anion and a cation, respectively. Application to the symmetric molten salt and molten sodium chloride manifests the significance of each contribution.