Phenomenological kinetics of Frenkel defect recombination and accumulation in ionic solids

This review deals with the theoretical study of the kinetics of the A+B to 0 biomolecular reaction between point Frenkel defects in irradiated solids. Three different approaches are discussed: macroscopic, mesoscopic and microscopic, and their advantages and shortcomings are analysed. Special attention is paid to the formalism of many-point particle densities and its application in the study of the effects of defect-density fluctuations. The kinetics of all recombination regimes are considered in detail, including static reactions, correlated annealing, diffusion- and hopping-controlled reactions, and aggregation of immobile defects under the conditions of a permanent defect source (irradiation). Problems rarely discussed in the literature are emphasized: transient kinetics; effects of long-range hop lengths and of defect interaction; cooperation phenomena at high defect densities and for long reaction times; and accuracy of Kirkwood's superposition approximation. Theory is illustrated by relevant experimental data for ionic crystals.