Hindered Rotational Energy Barriers of BH4– Tetrahedra in β-Mg(BH4)2 from Quasielastic Neutron Scattering and DFT Calculations
| Autor: | J. Kheres, B.C. Hauback, Aline Léon, M. D. Riktor, J. Wuttke, Kim Lefmann, Jon Bergmann Maronsson, Fanni Juranyi, Dadi Þorsteinn Sveinbjörnsson, E. Gil Bardaji, Maximilian Fichtner, Didier Blanchard, Tejs Vegge |
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| Rok vydání: | 2012 |
| Předmět: |
Chemistry
Resolution (electron density) Rotation around a fixed axis chemistry.chemical_element Activation energy Neutron scattering Molecular physics Surfaces Coatings and Films Electronic Optical and Magnetic Materials Rotational energy Crystallography General Energy Quasielastic neutron scattering Density functional theory Physical and Theoretical Chemistry Boron |
| Zdroj: | The Journal of Physical Chemistry C. 116:2013-2023 |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/jp208670v |
| Popis: | In this work, hindered rotations of the BH4– tetrahedra in Mg(BH4)2 were studied by quasielastic neutron scattering, using two instruments with different energy resolution, in combination with density functional theory (DFT) calculations. Two thermally activated reorientations of the BH4– units, around the 2-fold (C2) and 3-fold (C3) axes were observed at temperatures from 120 to 440 K. The experimentally obtained activation energies (EaC2 = 39 and 76 meV and EaC3 = 214 meV) and mean residence times between reorientational jumps are comparable with the energy barriers obtained from DFT calculations. A linear dependency of the energy barriers for rotations around the C2 axis parallel to the Mg–Mg axis with the distance between these two axes was revealed by the DFT calculations. At the lowest temperature (120 K) only 15% of the BH4– units undergo rotational motion and from comparison with DFT results it is expectedly the BH4– units with the boron atom closest to the Mg–Mg axis, although dynamics related to... |
| Databáze: | OpenAIRE |
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