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arXiv · 0707.4604

Electronic and Vibrational Properties of gamma-AlH3

Yan Wang·Jia-An Yan·M. Y. Chou
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Abstract

Aluminum hydride (alane) AlH_3 is an important material in hydrogen storage applications. It is known that AlH_3 exists in multiply forms of polymorphs, where $α$-AlH_3 is found to be the most stable with a hexagonal structure. Recent experimental studies on $γ$-AlH_3 reported an orthorhombic structure with a unique double-bridge bond between certain Al and H atoms. This was not found in $α$-AlH_3 or other polymorphs. Using density functional theory, we have investigated the energetics, and the structural, electronic, and phonon vibrational properties for the newly reported $γ$-AlH_3 structure. The current calculation concludes that $γ$-AlH_3 is less stable than $α$-AlH_3 by 2.1 KJ/mol. Interesting binding features associated with the unique geometry of $γ$-AlH3 are discussed from the calculated electronic properties and phonon vibrational modes. The binding of H-s with higher energy Al-p,d orbitals is enhanced within the double-bridge arrangement, giving rise to a higher electronic energy for the system. Distinguishable new features in the vibrational spectrum of $γ$-AlH_3 were attributed to the double-bridge and hexagonal-ring structures.

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Yan Wang, Jia-An Yan, M. Y. Chou. 2007-07-31. Electronic and Vibrational Properties of gamma-AlH3. https://doi.org/10.1103/physrevb.77.014101

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