Towards suppressing H blistering by investigating the physical origin of the H-He interaction in W

We investigate the physical origin of H-He interaction in W in terms of optimal charge density by calculating the energetics and diffusion properties using a first-principles method. On the one hand, we show a strong attraction between H and He in W originated from the charge density redistribution due to the presence of He, driving H segregation towards He. This can block the permeation of H into deeper bulk and thus suppress H blistering. On the other hand, we demonstrate that He, rather than H, energetically prefers to occupy the vacancy centre due to its closed-shell structure, which can block H2 formation at the vacancy centre. This is because He causes a redistribution of charge density inside the vacancy to make it 'not optimal' for the formation of H2 molecules, which can be treated as a preliminary nucleation of the H bubbles. We thus propose that H retention and blistering in W can be suppressed by doping the noble gas elements.