Stability and energetics of HenVm complexes in Fe–Cr alloys: Ab initio study

Abstract

Density functional theory (DFT) calculations have been implemented to investigate the helium trapping effect in multi-vacancies, and the stability and energetics of HenVm complexes (n = 0–6, m = 0–4). The existence of Cr inhibits the capture of helium atoms in multiple vacancies to some extent. A stronger helium self-trapping aggregation than that in pure iron was found in Fe–Cr alloys. In the early stage of nucleation, the HenVm complexes with higher density in Fe–Cr alloys provide more annihilation sites for the irradiation induced recombination of Frankel pairs, and have higher irradiation swelling resistance than pure iron. A new mechanism has been found that the possibility of the formation of helium-vacancy complexes depends on the helium atoms (n) or vacancies (m). Our simulation results corroborate that when the n/m ratio tends to increase, there is spontaneous emission of helium atoms or self-interstitial atoms (SIAs), and it is difficult to grow helium-vacancy-type complexes in Fe–Cr alloys, which provides necessary information for explaining complex experimental phenomena.