Cascade debris overlap mechanism of ⟨100⟩ dislocation loop formation in Fe and FeCr

Two types of dislocation loops are observed in irradiated alpha-Fe, the 1/2 < 111 > loop and the < 100 > loop. Atomistic simulations consistently predict that only the energetically more favourable 1/2 < 111 > loops are formed directly in cascades, leaving the formation mechanism of < 100 > loops an unsolved question. We show how < 100 > loops can be formed when cascades overlap with random pre-existing primary radiation damage in Fe and FeCr. This indicates that there are no specific constraints involved in the formation of < 100 > loops, and can explain their common occurrence. Copyright (C) EPLA, 2017