Coexistence of a self-interstitial atom with light impurities in a tungsten grain boundary

In this paper, we report on ab initio simulations results focused on completing a thorough energetic, structural, charge and mobility analysis of the synergistic behaviour of diverse defects, namely self-interstitial atoms (SIA) and light impurity atoms (LIA), i.e., He and H, that would appear in W when simultaneously irradiated with the latter. In particular, the influence of a W(110)/W(112) grain boundary (GB) in the behaviour of coexisting defects is studied and compared with the results obtained in the bulk. Four possible scenarios are analysed concerning the occupation of the GBs with: (i) a single SIA (ii) the simultaneous presence of two different defects, that is, He-H or SIA-LIA pairs, and (iii) the three types of defects together. The most stable configuration in each of these scenarios is detailed. Results show that GBs act as trapping sites for SIAs and LIAs and that the interaction between He and H is weak in all the analysed arrangements. They also indicate that the introduction of a SIA in a GB preloaded with He and H affects each of the atoms differently, as the former tends to stay close to the extra W atom, while the latter finds more comfortable accommodations away from the other two defects. In bulk W, the qualitative behaviour of He and H is quite similar and the presence of a LIA strongly affects the pre-ferred orientation of the SIA dumbbell. Additionally, defect mobilities along the GB have been assessed concluding that the SIAs tend to move along the interfacial grooves, so to recombine with the vacancies present there. (c) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

In this paper, ab initio simulations were conducted to analyze the synergistic behavior of diverse defects in W, including self-interstitial atoms (SIA) and light impurity atoms (LIA) such as He and H. The influence of a W(110)/W(112) grain boundary (GB) on the coexisting defects was studied and compared with bulk results. The results showed that GBs act as trapping sites for SIAs and LIAs, and the interaction between He and H is weak. The behavior of defects in GBs differs from that in the bulk, and the presence of LIAs strongly affects the preferred orientation of SIA dumbbells. Additionally, the mobility of defects along the GB was assessed, and it was found that SIAs tend to move along the interfacial grooves to recombine with vacancies.