Dynamics of mobile ions in crystals, glasses and melts, described by the concept of mismatch and relaxation

Abstract

The concept of mismatch and relaxation (CMR) provides a model description for the dynamics of the hopping motion of ions in ion-conducting materials. The following applications are discussed. (i) In the crystalline fast ion conductor RbAg 4I 5 the CMR is employed to analyse the gradual transition from random to nonrandom hopping that is found to occur below 298 K. (ii) When used to describe the ion dynamics in fragile supercooled melts, the CMR yields a new equation for the temperature dependence of the dc conductivity. (iii) In interacting dipole systems, the nearly-constant-loss (NCL) behaviour is reproduced by the CMR. (iv) After introduction of a structure-sensitive parameter, the CMR is able to fit experimental conductivity spectra that display significant differences in shape.