Discrete-lattice theory for Frenkel-defect aggregation in irradiated ionic solids

A microscopic theory of diffusion-controlled aggregation of radiation Frenkel defects-called in ionic solids H and F centers-is presented. This is based on a discrete-lattice formalism for the single defect densities (concentrations) and the coupled joint densities of similar and dissimilar defects treated in terms of a modified Kirkwood superposition approximation. The kinetics of defect aggregation is studied in detail; the cooperative character of this process for both types of complementary defects is shown. The theory is applied to the description of the kinetics of metal colloid formation during heating of electron-irradiated CaF2 crystals.