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ab-initio modelling of Mg:H interstitial solid solutions

Published online by Cambridge University Press:  26 February 2011

M. Messina ,
F. Cleri  and
M. Volpe
M. Messina
Affiliation:
Ente Nuove Tecnologie, Energia e Ambiente (ENEA), Unità Materiali e Nuove Tecnologie, Centro Ricerche Casaccia, 00100 Roma A. D. (Italy)
F. Cleri
Affiliation:
Ente Nuove Tecnologie, Energia e Ambiente (ENEA), Unità Materiali e Nuove Tecnologie, Centro Ricerche Casaccia, 00100 Roma A. D. (Italy)
M. Volpe
Affiliation:
Ente Nuove Tecnologie, Energia e Ambiente (ENEA), Unità Materiali e Nuove Tecnologie, Centro Ricerche Casaccia, 00100 Roma A. D. (Italy)
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Abstract

We studied the thermodynamics of interstitial Mg:H solid solutions by means of ab-initio electronic structure calculations. Soft pseudopotentials (Troullier-Martins) with non linear core correction and Perdew-Burke-Ernzerhof GGA exchange-correlation functional were employed, in the framework of a DFT plane-wave scheme. We inserted increasing concentrations of interstitial H atoms in the hcp Mg lattice, in both tetrahedral and octahedral positions. We calculated the heat of solution and the volume variation as a function of H concentration. Although the difference in Gibbs free energy is positive at any H concentration above 10−6 at.%, our results show that the enthalpic contribution is negative at any H concentration, therefore locally favouring H clustering. This reflects the existence of a driving force for the subsequent formation of the hydride. The volume deformation was characterized, finding that octahedreal interstitials have a minor effect, while tetrahedral interstitial can induce very large local expansion.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 801: Symposium BB – Materials and Technologies for a Hydrogen Economy , 2003 , BB3.5
Copyright
Copyright © Materials Research Society 2004

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References

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