JUMP RELAXATION IN RBAG4I5 BY DYNAMIC CONDUCTIVITY AND QUASI-ELASTIC NEUTRON-SCATTERING

The hopping dynamics of the highly mobile silver ions in RbAg4I5 is analyzed by a novel combination of experimental and modelling techniques. The results presented in this paper include: (i) a complete set of conductivity spectra of RbAg4I5 from 4 MHz to 105 GHz, (ii) a quasielastic neutron scattering study on a large single crystal of RbAg4I5, and (iii) a modelling of the non-random hopping motion of the silver ions. In our model conception devised for RbAg4I5 two kinds of hops are discerned; one is a priori unsuccessful, while the other is potentially successful. This modified jump relaxation model yields excellent fits to the conductivity spectra. For the interpretation of the quasielastic neutron scattering data a generalized Chudley-Elliott equation is formulated which accounts for the frequent forward-backward hopping of the ions. Incoherent model spectra calculated from this equation are found to coincide with the experimental spectra which are essentially coherent. Identical parameter values provide a simultaneous successful interpretation of both conductivity and neutron scattering results when the modified jump relaxation model is applied.