Electronic structures of nickel metal with hydrogen impurity

By using a first-principles numerical method, the electronic structures of face-centered cubic Ni doped with H, H⁺ and H^- are investigated. In two adopted cluster models, H occupies the centers of octahedron and tetrahedron as interstitial. It was found that the former is preferentially occupied. The constructed Ni-H, Ni-H⁺ and Ni-H^- bonds are only slightly different due to electron flowing. The residual (doping H^- ) or insufficient (doping H⁺ ) electrons are basically absorbed or supplied by the further matrix atoms. The additions induce a strong reduction of the interactions between their first neighbor atoms, but a weaker alteration of those between their first and second neighbors, which is the expression of hydrogen local effect and can be regarded as an explanation of hydrogen embrittlement.