Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 42: Functional materials III: Actuators, sensors and functional devices

MM 42.3: Vortrag

Mittwoch, 9. März 2016, 16:15–16:30, H53

High-pressure polymorphism as a step towards high density structures of LiAlH4 — Xiaoli Huang, Defang Duan, Fangfei Li, Lu Wang, Gang Wu, Bingbing Liu, and •Tian Cui — State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, P. R. China

Ternary aluminum hydrides could be an extremely efficient energy storage system owing to their high gravimetric and volumetric hydrogen densities. Of these, LiAlH4 is a prominent hydrogen-storage material with 10.6 wt% theoretical hydrogen content and thus has recently received much attention. The search for polymorphism with high volumetric hydrogen densities is a key resource for hydrogen storage materials. The great interest in high pressure phase transformations of LiAlH4 has been aroused by a theoretical prediction of a new high pressure phase. However, the crystal structures as the key to understand the intriguing high pressure behavior of LiAlH4 remained elusive for several decades. In order to clearly explore the behavior of LiAlH4 under high pressure, we have investigated the high pressure structures of LiAlH4 by a joint theoretical and experimental study. And we have uncovered two crystal structures (β-LiAlH4 and γ-LiAlH4) as metastable low-energy polymorphs, which are not reported in previous literatures. The first phase transition is accompanied by the local structure change from a distorted AlH4 tetrahedron into a distorted AlH6 octahedron, which contributes to a large volume collapse with 20%. This new structure may show completely different hydrogen storage properties if stabilized by chemical substitution at ambient pressure.