Abstract
The stability of magnesium hydride (MgH x ) nanoparticles (x = 0.5, …, 2) is investigated using ab initio calculations. It is shown that for a nanoparticle diameter of D ∼ 5 nm, the internal pressure becomes lower than 3 kbar; for this reason, the structure of hydride nanoparticles coincides with the structure of this hydride in crystalline form. It is found that the phase of partly saturated MgH x hydrides (x < 2) must decompose into the phase of pure hcp magnesium and the α phase of MgH2. The frequencies of jumps of hydrogen atoms within the hcp phase of magnesium and in the α phase of MgH2 are calculated; it is shown that slow diffusion of hydrogen in magnesium is due to the large height of potential barriers for motion of hydrogen within MgH2. To attain high diffusion rates, the structures of Mg53Sc and Mg53Ti crystals and their hydrides are calculated. It is found that the frequency of jumps of H atoms in Mg53ScH108 near the Sc atoms does not noticeably change as compared to the frequency of jumps in the α phase of MgH2, while the frequency of jumps in Mg53TiH108 near Ti atoms is higher by approximately a factor of 2.5 × 106. This means that diffusion in manganese hydride with small admixtures of titanium atoms must be considerably eased. Chemical dissociation of hydrogen molecules on the (0001) surface of hcp magnesium, on the given surface with adjoined individual Ti atoms, and on the surface of a one-layer titanium cluster on the given surface of magnesium is investigated. It is found that dissociation of hydrogen at solitary titanium atoms, as well as on the surface of a Ti cluster, is facilitated to a considerable extent as compared to pure magnesium. This should also sharply increase the hydrogen adsorption rate in magnesium nanoparticles.
Similar content being viewed by others
References
J. L. Slack, Sol. Energy Mater. Sol. Cells 90, 485 (2006).
K. Higuchi, J. Alloys Compd. 330, 526 (2002).
D. Kyoi, T. Sato, E. Ronnebro, et al., J. Alloys Compd. 372, 213 (2004).
P. Hohenberg and W. Kohn, Phys. Rev. 136, 864 (1964).
W. Kohn and L. J. Sham, Phys. Rev. 140, 1133 (1965).
G. Kresse and J. Hafner, Phys. Rev. B: Condens. Matter 47, 558 (1993).
G. Kresse and J. Hafner, Phys. Rev. B: Condens. Matter 49, 14251 (1994).
G. Kresse and J. Furthmüller, Phys. Rev. B: Condens. Matter 54, 11169 (1996).
D. Vanderbilt, Phys. Rev. B: Condens. Matter 41, 7892 (1990).
S. Wei, Phys. Rev. B: Condens. Matter 50, 4859 (1994).
G. Wulff, Z. Kristallogr. Mineral. 34, 449 (1901).
C. Herring, Phys. Rev. 82, 87 (1951).
P. Vajeeston, Phys. Rev. Lett. 89, 175506 (2002).
G. Mills, H. Jonsson, and G. K. Schenter, Surf. Sci. 324, 305 (1995).
G. Liang, J. Huot, S. Boilb, et al., J. Alloys Compd. 292, 247 (1999).
Author information
Authors and Affiliations
Corresponding author
Additional information
Original Russian Text © A.S. Fedorov, M.V. Serzhantova, A.A. Kuzubov, 2008, published in Zhurnal Éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2008, Vol. 134, No. 1, pp. 156–163.
Rights and permissions
About this article
Cite this article
Fedorov, A.S., Serzhantova, M.V. & Kuzubov, A.A. Analysis of hydrogen adsorption in the bulk and on the surface of magnesium nanoparticles. J. Exp. Theor. Phys. 107, 126–132 (2008). https://doi.org/10.1134/S1063776108070121
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S1063776108070121