Kinetic Monte Carlo simulations applied to irradiated materials: The effect of cascade damage in defect nucleation and growth

Kinetic Monte Carlo is used extensively in the field of radiation effects to understand damage accumulation and growth under irradiation. These calculations require previous knowledge on the formation of these defects, the relative stabilities of the different types of defects, their interactions and their mobilities. Many of these parameters can be extracted from molecular dynamics calculations using empirical potentials or from ab initio calculations. However, the number of parameters necessary for a complete picture is rather large. Kinetic Monte Carlo can be used as a tool to isolate those parameters that most influence the outcome of the calculations. In this paper, we focus on one aspect: the form of the damage after the collision cascade. We describe the effect of the form of the cascade as obtained from molecular dynamics simulations on damage accumulation. In particular, we demonstrate that the form of the cascade drastically changes the nucleation and growth of helium-vacancy clusters, possible precursors of voids and bubbles. Finally, we point to those open questions that need to be resolved to develop a truly predictive kinetic Monte Carlo model.