Irradiation‐induced defects in alkali halide crystals

Abstract

Abstract Models are presented for the successive stages of aggregation and recombination of radiation‐induced defects in alkali halides. The construction of our models is assisted by the calculation of defect energies. We concentrate on three main areas: firstly, we consider initial aggregation of H centres, where we propose the formation of a weakly bound di‐H centre which collapses into a neutral halogen molecule occupying an interstitial site. Secondly, we consider the thermodynamics of formation of the interstitial loops detected in the electron microscope by Hobbs, Hughes and Pooley (1973). We confirm the previously proposed mechanism by which the loops are created; this involves the displacement of lattice ions to dislocation loops by halogen molecules which occupy the vacancy pairs created. Thirdly, we consider the mechanism of annealing of metal colloids, and suggest that the vacancy‐molecule complexes, which are created together with the dislocation loops, may play an important role.