A first-principles study was made of the diffusion-controlled aggregation of Frenkel defects (interstitial atoms and vacancies) in solids under irradiation. A novel theory was presented which was based upon the discrete-lattice formalism of single-defect densities (concentrations), and the coupled joint densities of similar and dissimilar defects; treated in terms of the Kirkwood superposition approximation. The conditions which were required for the efficient aggregation of vacancies and interstitials were studied, and a cooperative nature of the aggregation process was identified.

V.Kuzovkov, E.Kotomin: Journal of Physics - Condensed Matter, 1995, 7[37], L481-6