On the correlation between primary damage and long-term nanostructural evolution in iron under irradiation

Atomic displacement cascades in solids are complex phenomena, the outcome of which can be statistically characterised by properties such as their spatial extent, morphology and the spatial correlation of defects. Some properties scale in a simple way with parameters such as the cascade energy, others have limited variability with energy, for example point defect cluster size distributions. Taking advantage of the latter invariance, we use object kinetic Monte Carlo simulations to demonstrate that most properties of displacement cascade play no significant role in the evolution of point defect cluster size distributions after long enough time. It is suggested that reliable long-term predictions are possible, when using only the self-interstitial and vacancy cluster size distributions from low energy displacement cascades as building blocks to represent the complete spectrum of cascade energies obtained under neutron irradiation conditions. This is shown on the basis of recursive properties of displacement cascades evidenced for the first time and taking only approximately into account the average volumes in which vacancies and self-interstitial atoms are confined.The model has been successfully used to simulate the evolution of point defect clusters in iron for displacement rates in the range of 10−6 dpa/s and doses of the order of 0.1 dpa. The applicability beyond this range and to more complex materials is discussed.