Atomic modeling assessment of the interaction distance and effective bias for small defect clusters absorption at a void in BCC Fe

Abstract

Cavity swelling plays a vital role in the microstructural evolution of ferritic-martensitic alloys under irradiation. Recent research reported that the classic thermal criterion of the critical size in cavity growth loses its explanatory power outside the intermediate temperature regimes. In contrast, the newly proposed bias-driven criterion performs nearly equivalently at the entire temperature range by introducing the concept of cavity bias. Molecular statics calculations were performed to determine the interaction energy landscape of single self-interstitial atom (SIA), single vacancy, di-SIA, di-vacancy, 7-SIA cluster, and 7-vacancy cluster interaction with a 59-vacancy void in BCC Fe. Additionally, molecular dynamics simulations were conducted to investigate the rotation and migration behavior of varying size SIA clusters in close proximity to the void. A homogenization method was established to describe the capture volume and mimic the one-dimensional diffusion behavior for large SIA clusters. The interaction distance between the void and defects was determined, and the effective bias was calculated as a function of the void size at 25 ℃, 300 ℃, and 500 ℃. The results provide important atomistic inputs for mesoscale modeling of defect evolution and microstructural changes, such as cluster dynamics simulation.