Impact of PKA energy and spatial correlation of primary damage on irradiation microstructure evolution in iron: An object kinetic Monte Carlo simulation

Object kinetic Monte Carlo (OKMC) simulations were performed to investigate irradiation-induced microstructural evolution in bcc Fe, focusing on the effects of PKA energies of neutrons and the spatial distribution of primary defects. Molecular Dynamics (MD) simulations were applied to generate displacement cascades in a wide range of PKA energies, leading to different defect distributions after primary damage stage. OKMC simulations were conducted from 300 °C to 500 °C with a dose rate from 10 –5 dpa/s to 10 –3 dpa/s and a total dose of 1.0 dpa. The simulation results demonstrate that increasing PKA energy elevates the number density of vacancy and SIA clusters by one to two orders of magnitude while only slightly reducing their average size. The influence of spatial correlations of cascade debris was further investigated by randomizing the defect clusters in the whole simulation box, neglecting their intra-cascade recombination and self-clustering. Results indicate that the absence of spatial correlations significantly underestimates the number density of vacancy and SIA clusters while overestimating their cluster sizes. Notably, these effects weaken with increasing PKA energy, and even diminish at high temperatures and low dose rates. This work provides fundamental insights into the effect of PKA energy on the long-term evolution with a focus on the spatial correlation after primary damage stage and offer novel insights into accurate prediction of long-term microstructural evolution through mesoscopic methods.