H dissolution and desorption near He-V complexes in W surfaces with different orientations

Understanding the influence of helium-vacancy (He-V) complexes on hydrogen (H) behaviors in different tungsten (W) surfaces is critical for designing new plasma-facing materials to inhibit H retention and surface damage under H-He-neutron synergetic irradiation. DFT calculations are performed to explore H dissolution and desorption near He-V complexes in W (110), W (100) and W (111) surfaces. We found that, it is most difficult for H dissolution but easiest for H trapping by He-V complexes in the W (110) surface, while the opposite is true in the W (111) surface. When He-V complexes are near W surfaces, the difficulty levels of H diffusion from bulk to surface and desorption increased in the order of (100), (110), and (111). Therefore, the W (110) surface that can inhibit H dissolution would be the best while the W (111) the worst for resisting H retention and surface damage. Based on these mechanisms, we have further proposed a general formula of potential energy to describe H dissolution, diffusion and trapping from surface into bulk in metals.