Orientation-dependent behaviors of H dissolution and diffusion near W surfaces: A first-principles study

The dissolution and diffusion behaviors of H in the four low-Miller-index W surfaces ((110), (112), (100) and (111)) are systematically studied by the density functional theory approach to understand the orientation dependence of the H bubble distribution on surface. The results show that H accumulation on surface is influenced by H diffusion barrier as well as vacancy and H formation. The barriers of diffusion towards surfaces are larger than that in bulk. It indicates that H is prone to diffuse into the deep in bulk once H dissolves in surface. H is preferred to accumulate on the W(111) surface due to the lower formation energies of vacancy and H comparing to that in bulk. However, W(110) is the resistant surface for forming H bubble due to the higher formation energies of vacancy and H. The results are helpful for understanding the orientation dependence of surface damages on W surface and designing new plasma-facing materials.