Energetics and diffusional properties of helium in W-Ta systems studied by a new ternary potential

In this paper, we present an interatomic potential for the ternary W–Ta–He system, which is an extension of our previous W–Ta potential. The new potential parameters for the W–He and Ta–He interactions are determined by fitting the results obtained from first-principles calculations. The formation energies of a single He atom at different sites, the binding energies of He–He and He–Vac (Vac = vacancy) in W/Ta, and the binding energies of a single He atom with a solute Ta atom in W are used as the fitting targets. Then, the binding energies of an additional interstitial He atom to existing He_nVac_m clusters in W/Ta are calculated, and the results reported correspond with the results from the first-principles. Furthermore, the effects of solute Ta on the diffusion and aggregation of He in bulk W are studied. We observed that small interstitial He atom clusters (N_He ≤ 4) were easy to diffuse in pure W, and their diffusion activation energies were less than 0.3 eV. However, the binding energies between Ta and these clusters were between 0.5 and 0.9 eV, which has a pinning effect on the He cluster diffusion. At high temperature, the solute Ta cannot qualitatively hinder the agglomeration of He atoms, however, due to the pinning effect compared with pure W, solute Ta in W has a certain delay effect on the agglomeration of He atoms in time.