A coarse-graining model for ions in water

Abstract

Over more than 100 years, water diffusivity in ionic solutions has been a matter of debate and still some gaps need to be filled in order to understand and reproduce experimental results at their best. Here a coarse-grained model for ions in water is used to test the empirical Jones-Dole relation as well as to study the behaviour of the so-called “structure breaker” and “structure maker” ions. The model reproduces qualitatively the experimental phenomenology by assuming that the main effects of the ions is on the intensity of the water hydrogen bonds. The model clarifies that, at fixed temperature, the Jones-Dole relation holds only for a limited range of concentrations that depends on pressure. The breakdown of the Jones-Dole marks also the end of the simplified distinction between “structure breaker” and “structure maker” ions