Simulation of defect evolution in irradiated materials: Role of intracascade clustering and correlated recombination

The evolution of damage produced by collision cascades in Fe is studied using both kinetic Monte Carlo (kMC) and rate theory (RT) approaches. The initial damage distribution is obtained from molecular-dynamics simulations of 300.3em0exkeV recoils in Fe. An isochronal annealing is simulated to identify the different thermally activated mechanisms that govern defect evolution. When clusters form during collision cascades, kMC simulations show that additional recovery peaks should be expected, in comparison to recovery curves obtained under electron irradiation conditions. Detailed kMC and RT simulations reveal that some of these recovery peaks are due to correlated recombinations at low temperature between defects. In particular, we show that under cascade-damage conditions it is possible to observe correlated recombinations between vacancies and self-interstitial clusters. These correlated recombinations cannot be reproduced with a RT model, and therefore kMC and RT differ at low temperature. However, for the conditions presented here, the contribution of correlated recombination is very small and therefore no significant differences are observed at high temperatures between these two models.