Session F3: Materials/Nanomaterials Science
1:00 PM–4:12 PM, Friday, November 13, 2009
Spanagel Room: 321
Chair: Michelle Poliskie, Solyndra
Abstract ID: BAPS.2009.CAL.F3.6
Abstract: F3.00006 : Comparative analysis of the hydrogen-vacancy interaction in Mg and Al based on density functional theory
2:00 PM–2:12 PM
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Abstract 
Authors:
Lars Ismer
(Materials Department, University of California, Santa Barbara, CA 93106-5050)
A. Janotti
(Materials Department, University of California, Santa Barbara, CA 93106-5050)
C.G. Van de Walle
(Materials Department, University of California, Santa Barbara, CA 93106-5050)
The interactions of vacancies (V) with atomic hydrogen (H) in the bulk of the metal are expected to play an important role in H-storage as well as H-embrittlement. Using density functional theory we have studied the H-V interactions in hcp-Mg and fcc-Al, two prototypic systems for H storage. We show that a single V can in principle host up to 9 H atoms in Mg and 10 in Al. In going beyond previous theoretical studies we further evaluate the concentration of the H-V complexes for different H loading conditions -- ranging from low pressures to high pressures of H2 gas. We find significant differences between Mg and Al. In the case of Al, up to 15 {\%} of H atoms are trapped in single vacancies even for very low H pressures, which strongly slows down the diffusion of H atoms. In the case of Mg, these trapping effects are negligible for low H pressures. However, vacancies containing multiple H atoms and H-induced superabundant vacancy formation are predicted to occur in Mg at much lower H loading pressures (about 1 GPa) than in Al (about 10 GPa).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.CAL.F3.6