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MM: Fachverband Metall- und Materialphysik
MM 12: Postersitzung I
MM 12.26: Poster
Monday, March 14, 2011, 17:30–19:00, P5
Comparative analysis of hydrogen-vacancy interactions in Mg and Al based on density functional theory — •Lars Ismer1, Min Sik Park2, Anderson Janotti1, and Chris G Van de Walle1 — 1University of California at Santa Barbara, CA 93106 — 2Missouri University of Science and Technology, Rolla, MO 65409
For hydrogen storage in metals the presence of vacancies in the bulk of the metal and their interactions with atomic hydrogen (H) plays an important role. Using density functional theory we have studied the H-vacancy interactions in hcp-Mg and fcc-Al, two prototypic systems for H storage. We show that a single vacancy can host up to 9 H atoms in Mg and 10 in Al. In going beyond previous theoretical studies we evaluate the concentration of the H-vacancy complexes for different H loading conditions, ranging from low pressures to high pressures of H2 gas. We find strong 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 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).