Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 24: Functional Materials II
MM 24.2: Vortrag
Dienstag, 27. März 2012, 11:45–12:00, H 1029
First-principles study of La–H: structural change from LaH2 towards LaH3 — •Tobias C. Kerscher1,3, Gunther Schöllhammer1, Walter Wolf2, Stefan Müller3, Peter Herzig1, and Raimund Podloucky1 — 1University of Vienna, Institute of Physical Chemistry, Vienna, Austria — 2Materials Design s.a.r.l., Le Mans, France — 3Technische Universität Hamburg-Harburg, Institut für Keramische Hochleistungswerkstoffe, Hamburg, Germany
By combination of first-principles density functional theory (DFT) and a cluster expansion (CE) with the UNCLE code [1], we investigate the interesting changes in the La–H system for the region between LaH2 and LaH3.
These structural changes from the fluorite structure of the dihydride to the full trihydride drives a concentration-dependent metal-insulator transition (“switchable mirror”) at LaH≈ 2.8, as known by experiment. While our prior DFT study [2] had indeed already revealed the opening of a band gap at a hydrogen concentration close to LaH3, we now show how a CE—based on input from DFT—predicts the structural changes in the full concentration range: It reveals the hydrogen’s preference to occupy tetrahedral interstitial sites and the general formation of closely-paired hydrogen vacancies on octahedral interstitials.
We compare our results to experiment.
[1] D. Lerch et al., Modelling Simul. Mater. Sci. Eng. 17, 055003 (2009)
[2] G. Schöllhammer et al., J. Alloys Comp. 480, 111–113 (2009)