FREQUENCY-DEPENDENT RESPONSE AND DYNAMIC DISORDER

This paper discusses selected aspects of the application of dynamic percolation models to ionic transport in mixed-ion superionic conductors. The discussion is based on an AB lattice gas model with hard-core repulsions and a ratio tau, 0 less-than-or-equal-to tau less-than-or-equal-to infinity, between the transition rates of particles A and B. The frequency-dependent conductivity for a tracer particle is calculated within an effective-medium theory. The motion of the background B-particles is regarded as providing a fluctuating disordered environment for the tracer particles A. A crossover frequency separating high-frequency and low-frequency response is found which scales with tau as omega-c approximately tau-1/2. The results for the dc limit are compared with simulations and are found to be in very good agreement.