Dresden 2009 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 20: Poster Session I
MM 20.21: Poster
Tuesday, March 24, 2009, 14:45–16:30, P4
Low temperature Raman spectroscopy of Mg(BH4)2 and Mg(BD4)2 — •Florian Gebrt1, Britta Willenberg1, Joachim Schoenes1, Michiel van Setten2, Christoph Frommen2, and Maximilian Fichtner2 — 1Institut für Physik der Kondensierten Materie, TU Braunschweig, Germany — 2Institute of Nanotechnology, Forschungszentrum Karlsruhe, Germany
We report a micro-Raman scattering study on fine powders of Mg(BH4)2 and Mg(BD4)2 for temperatures ranging from approximately 5K to room temperature. At the lowest temperature, we observe 25 lines in both compounds, which were assigned within the 86 Raman active modes, for the I-4m2 structure, whose energies have been derived using first principle calculations based on density functional theory. This structure was claimed by Ozolins et al. [1] to posses an even lower ground state energy than the P61 structure reported formerly for the low temperature α-phase [2,3]. The comparison of theoretical and experimental values leads to straight lines with slopes between 0.98 and 1.03 for the external, bending and stretching modes, which is better than expected. Nevertheless, one can not definitively conclude that the structure is I-4m2 since a substantial number of possible lines have not been observed. This is even more so for the P61 structure. Further progress will require measurements on single crystals and/or intensity computations. [1] V. Ozolins et al., Phys. Rev. Lett. 100, 135501 (2008) [2] R. Cerný et al., Angew. Chem. Int. Ed. 46, 5765 (2007) [3] J.-H. Her et al. , J. Acta Cryst. B63, 561 (2007)