Study on synergistic effects of H and He in α-Fe

The synergistic effect of hydrogen and helium in α-Fe has been investigated using density functional theory calculation method. In perfect crystal of Fe, the presence of helium atom would decrease the dissolution energy of hydrogen atom near helium atom. This implies the existence of an attractive interaction between hydrogen and helium atoms. It is also revealed that the most stable places for both hydrogen and helium atoms are two tetrahedral sites (T-site) with a distance of 2.16 Å. Furthermore, a vacancy-helium complex (Va-He) would be an effective trapping site for hydrogen atom compared with mono-vacancy, a Va-He would be able to trap 8 hydrogen atoms.