Ab initio study of Al-doping effect on helium behaviors in scandium hydrides

Helium (He) in rare-earth metal hydrogen storage materials tends to aggregate and produce bubbles and release them, which has an impact on the lifetime of the materials. Therefore, it is crucial to study the aggregation behavior of He to improve the lifetime of the materials. In this paper, two forms of interstitial doping and substitution doping are selected by density-functional theory (DFT) calculations, and the effects of Al doping in ScH2 on the geometries, formation energies, and binding energies of He atoms, as well as the migration behaviors of the doped Al atoms on the migration of the He atoms are investigated in detail. Finally, it is demonstrated that Al doping in ScH2 makes it difficult for He atoms to exist near and stabilize the vacancies close to Al atoms, which is likely to inhibit the formation of clusters of He, and provides a strong basis for the realization of the improvement of helium-solidifying properties of ScH2 materials.