It was noted that, during cascade-producing irradiation with high-energy neutrons or charged particles, only a small fraction of the initially displaced atoms contributed to the population of free defects that was able to migrate through the metal and cause microstructural changes. Although computer simulations of free defect production might be thought to be best done by using molecular dynamics methods, the wide ranges of time and distance scales which were involved could in fact be handled by using a combination of atomistic models that used various levels of approximation. An atomic-scale multi-model approach was developed which combined molecular dynamics binary collision models with stochastic annealing simulations. Annealing simulations were used to calibrate binary collision simulations with regard to the results of molecular dynamics calculations, as well as to model the subsequent migration of defects at more macroscopic time- and size-scales. The results of simulating cascades in Cu were presented. The temperature dependence of free defect production, following the simulated annealing of isolated cascades in Cu, revealed a difference in the fractions of free vacancies and interstitial defects which escaped from cascades above stage-V. This difference was suggested to be a result of the direct formation of interstitial clusters in cascades and of the relative thermal stabilities of vacancy and interstitial clusters during subsequent annealing, and to be the basis for the production-bias mechanism of void swelling.

H.L.Heinisch: Nuclear Instruments and Methods in Physics Research B, 1995, 102[1-4], 47-50