en
Scientific article
English

NMR Study of Reorientational Motion in Alkaline-Earth Borohydrides: β and γ Phases of Mg(BH 4 ) 2 and α and β Phases of Ca(BH 4 ) 2

Published inJournal of physical chemistry. C, vol. 116, no. 7, p. 4913-4920
Publication date2012
Abstract

To study the reorientational motion of BH4 groups in β and γ phases of Mg(BH4)2 and in α and β phases of Ca(BH4)2, we have performed nuclear magnetic resonance (NMR) measurements of the 1H and 11B spin–lattice relaxation rates in these compounds over wide ranges of temperature and resonance frequency. It is found that at low temperatures the reorientational motion in β phases of Mg(BH4)2 and Ca(BH4)2 is considerably faster than in other studied phases of these alkaline-earth borohydrides. The behavior of the measured spin–lattice relaxation rates in both β phases can be satisfactorily described in terms of a Gaussian distribution of activation energies Ea with the average Ea values of 138 meV for β-Mg(BH4)2and 116 meV for β-Ca(BH4)2. The α phase of Ca(BH4)2 is characterized by the activation energy of 286 ± 7 meV. For the novel porous γ phase of Mg(BH4)2, the main reorientational process responsible for the observed spin–lattice relaxation rate maximum can be described by the activation energy of 276 ± 5 meV. The barriers for reorientational motion in different phases of alkaline-earth borohydrides are discussed on the basis of changes in the local environment of BH4 groups.

Research group
Citation (ISO format)
SOLONININ, Alexei V. et al. NMR Study of Reorientational Motion in Alkaline-Earth Borohydrides: β and γ Phases of Mg(BH 4 ) 2 and α and β Phases of Ca(BH 4 ) 2. In: Journal of physical chemistry. C, 2012, vol. 116, n° 7, p. 4913–4920. doi: 10.1021/jp210509g
Main files (1)
Article (Published version)
accessLevelRestricted
Identifiers
ISSN of the journal1932-7447
606views
0downloads

Technical informations

Creation03/01/2012 10:34:00 AM
First validation03/01/2012 10:34:00 AM
Update time03/14/2023 5:09:24 PM
Status update03/14/2023 5:09:23 PM
Last indexation01/15/2024 11:05:02 PM
All rights reserved by Archive ouverte UNIGE and the University of GenevaunigeBlack