Many-ion Dynamics: The Common View of CM and MC

For solution of the problem of conductivity relaxation and diffusion of ions in ionic conductors with high density of ions, it is essential not to neglect treatment of the effects of many-ion dynamics. This view is shared by the Coupling Model (CM) and the MIGRATION CONCEPT (MC), although the treatment, emphasis and some predictions of the two models are different. Notwithstanding, a basic element is common to both models, namely the primitive relaxation, which performs two important functions. It terminates the caged ion dynamics at short times and initiates the many-ion dynamics at longer times. We demonstrate by experiments and molecular dynamics simulations the existence of the primitive relaxation, and the two functions it performs. The relation of the primitive relaxation time to the conductivity relaxation time predicted by the CM is shown to hold in all cases considered.