Kinetic dielectric decrement revisited: phenomenology of finite ion concentrations

Abstract

With the help of a recently developed non-equilibrium approach, we investigate the ionic strength dependence of the Hubbard–Onsager dielectric decrement. We compute the depolarization of water molecules caused by the motion of ions in sodium chloride solutions from the dilute regime (0.035 M) up close to the saturation concentration (4.24 M), and find that the kinetic decrement displays a strong non-monotonic behavior, in contrast to the prediction of available models. We introduce a phenomenological modification of the Hubbard–Onsager continuum theory, which takes into account the screening due to the ionic cloud at the mean-field level and, which is able to describe the kinetic decrement at high concentrations including the presence of a pronounced minimum.