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Article overview
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Atomic hydrogen adsorption and incipient hydrogenation of the Mg(0001) surface: A density-functional theory study | | Yanfang Li
; Ping Zhang
; Bo Sun
; Yu Yang
; Yinghui Wei
; | | Date: |
28 Apr 2009 | | Abstract: | We investigate the atomic hydrogen adsorption on Mg(0001) by using
density-functional theory within the generalized gradient approximation and a
supercell approach. The coverage dependence of the adsorption structures and
energetics is systematically studied for a wide range of coverage and
adsorption sites. In the coverage range $0<Theta<1.0, the most stable among
all possible adsorption sites is the on-surface fcc site followed by the hcp
site, and the binding energy increases with the coverage, thus indicating the
higher stability of on-surface adsorption and a tendecy to the formation of H
islands (clusters) when increasing the coverage within the region
$0<Theta<1.0. The on-surface diffusion path energetics of atomic hydrogen, as
well as the activation barriers for hydrogen penetration from the on-surface to
the subsurface sites, are also presented at low coverage. At high coverage of
$1.00<Theta<2.0, it is found that the coadsorption configuration with 1.0
monolayer of H’s residing on the surface fcc sites and the remaining monolayer
of H’s occupying the subsurface tetra-I sites is most energetically favourable.
The resultant H-Mg-H sandwich structure for this most stable coadsorption
configuration displays similar spectral features to the bulk hydride MgH$_{2}$
in the density of states. The other properties of the H/Mg(0001) system,
including the charge distribution, the lattice relaxation, the work function,
and the electronic density of states, are also studied and discussed in detail.
It is pointed out that the H-Mg chemical bonding during surface hydrogenation
displays a mixed ionic/covalent character. | | Source: | arXiv, 0904.4387 | | Services: | Forum | Review | PDF | Favorites | |
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