Ion Mobility and Levitation Effect: Anomalous Diffusion in Nasicon-Type Structure

A molecular dynamics study of ion mobility as a function of the size of the mobile ion within Nasicon-type structures is reported. The self diffusivity exhibits an anomalous peak suggesting that the levitation effect exists even in ionic systems dominated by Coulomb interaction. This has important consequences in the diffusion of ions in chemical and biological systems. It is seen that high mobility of the ion is associated with the liquidlike radial distribution functions between the ion and the oxygen of the framework. The force on the ion due to the framework within which it is moving is found to be a minimum.