Hydrogen dissociation and incorporation on Mg17Al12(100) surface: A density functional theory study

Hydrogen adsorption, dissociation, and penetration on (in) Mg17Al12 (100) surface are studied extensively by DFT total-energy calculations. The adsorption geometries, dissociation barriers, various diffusion pathways, penetrative processes, and electronic structures were investigated. Results show that the atomic and molecular hydrogen forms prefer to be adsorbed on the Mg3-Mg3 bridge sites (C sites). Hydrogen molecules are dissociated on the surface with the minimum barrier energy of 0.63 eV. There are two stages in the process of hydrogen incorporation, which are hydrogen diffusion on the surface and the penetration from the surface into the subsurface. Two possible pathways of atomic hydrogen penetration from surface into subsurface are found. The calculations of electronic structures show that the hybridization between the s orbital of H and the s orbitals of Mg is major. The Mg-Mg bond on the outmost surface is shortened from 4.48 angstrom to 3.30 angstrom after the hydrogen adsorption on C sites, showing the strong interaction between Mg and H atoms. (C) 2016 Elsevier B.V. All rights reserved.