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Understanding the Formation Energy of Transition Metal Hydrides

Published online by Cambridge University Press:  01 February 2011

Huw J. Smithson ,
Dane Morgan ,
Anton Van der Ven ,
Chris Marianetti ,
Ashley Pedith  and
Gerbrand Ceder
Huw J. Smithson
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, U.K
Dane Morgan
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
Anton Van der Ven
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
Chris Marianetti
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
Ashley Pedith
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
Gerbrand Ceder
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
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Abstract

A detailed analysis of the formation energies of transition metal hydrides is presented. The hydriding energies are computed for various crystal structures using Density Functional Theory. The process of hydride formation is broken down into three consecutive, hypothetical reactions in order to analyse the different energy contributions, and explain the observed trends. We find that the stability of the host metal is very significant in determining the formation energy, thereby providing a more fundamental justification for Miedema's “law of inverse stability” [1] (the more stable the metal, the less stable the hydride). The conversion of the host metal to the structure formed by the metal ions in the hydride (fcc in most cases) is only significant for metals with a strong bcc preference such as V and Cr - this lowers the driving force for hydride formation. The final contribution is the chemical bonding between the hydrogen and the metal. This is the only contribution that is negative, and hence favourable to hydride formation. We find that it is dominated by the position of the Fermi level in the host metal.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 730: Symposium V – Materials for Energy Storage, Generation, and Transport , 2002 , V2.2
Copyright
Copyright © Materials Research Society 2002

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References

1. Miedema, A. R., J. Less Common Metals 32, 117 (1973).Google Scholar
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