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Issue 25, 2009
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A computational study of electronic structure, thermodynamics and kinetics of hydrogen desorption from Al- and Si-doped α-, γ-, and β-MgH2

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Abstract

First principles calculations of pure and Al- and Si-doped α-, γ-, and β-MgH2 were performed to investigate the influence of Al and Si as impurities and the presence of high pressure phases on the properties of hydrogen sorption of magnesium hydride. The ab initio plane wave pseudopotential method based on density functional theory within the generalized gradient approximation was used in the present study. The total energies of the considered systems were calculated as a function of cell volume to obtain material properties such as bulk modulus K0, equilibrium cell volume V0 and minimum energy E0(V0). From the density of states (DOS) analysis, it was shown that doping MgH2 with Al and Si caused a reduction in the band gaps of each of the three phases. The diminished band gaps made the Mg–H bond more susceptible to dissociation. The destabilization of the hydrides was reflected in the decreased heats of formation of the doped hydrides, with the following ΔHf order: Si < Al and β < γ < α. A 30.5% reduction in the activation energy barrier Eact for H2 desorption was calculated for the Al-doped α-MgH2(001) surface and a 15.5% decrease in Eact of the Si-doped γ-MgH2(001) surface was deduced, while doping with Al and Si increased the activation energy barrier for the β-MgH2 (001) surface drastically.

Graphical abstract: A computational study of electronic structure, thermodynamics and kinetics of hydrogen desorption from Al- and Si-doped α-, γ-, and β-MgH2

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Publication details

The article was received on 19 Jan 2009, accepted on 24 Mar 2009 and first published on 27 Apr 2009


Article type: Paper
DOI: 10.1039/B901115C
Citation: J. Mater. Chem., 2009,19, 4348-4355
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    A computational study of electronic structure, thermodynamics and kinetics of hydrogen desorption from Al- and Si-doped α-, γ-, and β-MgH2

    T. Kelkar and S. Pal, J. Mater. Chem., 2009, 19, 4348
    DOI: 10.1039/B901115C

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