RELAXATION DYNAMICS IN DISORDERED IONIC CONDUCTORS

A microscopic mechanism for understanding fractional power-laws in the ac-response of ionic conductors is discussed in terms of hopping of charged particles in disordered lattices. We review recent Monte-Carlo simulations for lattices with Gaussian disorder in the local site energies, which show that "anomalous diffusion" occurs at intermediate time-scales as a result of the interplay of Coulomb-interactions and structural disorder. A new model pertaining to ionic transport in oxid glasses is proposed, which emphasises the role of long-range Coulomb-potentials due to counter-ions. Implications with respect to other dynamic probes e.g. inelastic neutron scattering and ultrasonic attenuation are also briefly discussed.