First-principles study on the hydrogen trapping by vacancy and substitutional helium in W–Ta alloy

Abstract

In this work, a first-principles method is performed to investigate the interaction effect of hydrogen (H) with vacancy and substitutional helium (He) in tungsten and tantalum (W–Ta) alloy (atomic ratio of 1:1). The H atom occupies the tetrahedral interstitial site to a greater extent than the octahedral interstitial site. The formation energies of H atoms near the W and Ta vacancy (VacW and VacTa) are higher than those near the substitutional He at W or Ta lattice sites (HeSub-W and HeSub-Ta). The vacancy and substitutional He act like trapping sites and can capture up to 12H atoms. The formation energies of H clusters as a function of the number of H atoms exhibit a parabolic tendency. For the structures of VacTa and HeSub-Ta, the binding energies of the even number of H atoms are lower than those of the adjacent odd number of H atoms. The abovementioned analysis provides an insight into the fundamental interactions of H point defects and H clusters in W–Ta alloy.

Keywords

• Hydrogen clusters
• Vacancy
• Substitutional He
• W–Ta alloy
• First-principles calculation