Abstract
The three low index surfaces of nickel, {100}, {110} and {111}, have been investigated to question the crystallographic orientation impact on hydrogen diffusivity and solubility near the surface. Diffusion profiles from Top adsorption sites underlined that subsurface migration barriers were different from the bulk and vary depending on the crystallographic orientation, revealing a local anisotropic diffusive behavior. The local geometry change of the successive occupied octahedral sites due to surface relaxation and H incorporation have also been investigated using nickel atoms positions of relaxed structures. The surface contraction effect on local octahedral sites appeared to be comparable to a vacancy effect on its nearest neighboring sites, both in terms of spatial extend and contraction magnitude. The hydrostatic contribution to H incorporation seemed to dominate the associate internal elastic energy, leading to a good description of local H solubility with the available volume. Local anisotropy at the surface proximity in terms of diffusivity and solubility were contained within the first atomic layers.
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