Theory. 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.