| Summary: | Effect of Ti/Y/O element on helium (He) clustering in vacancy (Vac) defect of vanadium (V) alloy were investigated using first-principles calculations. We first calculated the formation and binding energies of Hen clusters in Vac–X (X = O/O–Ti/O–4Ti/O–3Ti–Y) configurations, the values for O–3Ti–Y configuration are obviously reduced by 0.2–1.6 eV with respect to those of alone Vac. In the presence of O, He still favors the octahedral interstitial site at a Vac. The formation energies of Hen clusters in Vac–O–Ti and Vac–O–4Ti defects are close to those of Vac–O with n = 1–5 (n represents the number of He), which are higher than those of Vac by 3 %. 3Ti–Y considerably increases the formation energies of Hen clusters in Vac–O–3Ti–Y complex over 20 %. The nth He binding energy with Vac–X–Hen−1 shows a decreasing fluctuant trend, the attraction of Vac–O–3Ti–Y to He is the smallest among all considered configurations. The presence of Ti-O/Y-Ti-O/O obviously reduce the stability of Vac–He clusters. In addition, we discussed the de-trapping behaviors of He from the Vac–X–Hen complexes and found Hen clusters more easily de-trapped from the Vac–X configuration. The present results show that the formation of Vac–X complex reduces vacancy-trapping ability for more He impurities, leading to lots of small Vac–X–He cluster formation, hindering the formation of larger Hen clusters (He bubbles) in V alloys under irradiation.
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