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MM: Fachverband Metall- und Materialphysik

MM 22: Hydrogen in Metals

MM 22.2: Vortrag

Dienstag, 23. März 2010, 10:30–10:45, H5

First-principles studies of the La-H system — Gunther Schöllhammer¹, Peter Herzig¹, Walter Wolf², •Tobias Kerscher³, and Stefan Müller³ — ¹Institut für Physikalische Chemie, Universität Wien, 1090 Wien, Austria — ²Materials Design s.a.r.l., 72000 Le Mans, France — ³Universität Erlangen-Nürnberg, Lehrstuhl für Theoretische Physik 2, Staudtstr. 7, 91058 Erlangen, Germany

The LaH system is the epitome of an interesting candidate for theoretical investigations: Its structural details are still not well understood, and – at LaH_{≈ 2.8} – a concentration-dependent metal-insulator transition (“switchable mirror”) is observed. At low H concentrations our first-principles study found a preference of the H atoms for the occupation of the octahedral interstitial sites instead of the expected tetrahedral sites. Close to LaH₃ a stabilization of the structure either by an orthorhombic distortion or by the presence of (pairs of) H vacancies was observed. This coincides with opening up a band gap predicted via density functional theory [1]. Recently we have applied the cluster-expansion approach (see e.g. [2]) in the framework of the UNCLE code [3] in order to study configurational diversity. The objective is the calculation of a phase diagram from first-principles.
[1] G. Schöllhammer, W. Wolf, P. Herzig, K. Yvon, P. Vajda, J. Alloys Comp. 480, 111–113 (2009)
[2] S. Müller, W. Wolf, R. Podloucky, Ab-initio Methods and Applications, in Alloy Physics, ed. W. Pfeiler, Wiley 2007
[3] D. Lerch et al, Modelling Simul. Mater. Sci. Eng. 17, 055003 (2009)