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Interplay between the Reorientational Dynamics of the B3H8- Anion and the Structure in KB3H8

Published

Author(s)

M. S. Andersson, Jakob Grinderslev, X.-M. Chen, X. Chen, Ulrich Haussermann, Wei Zhou, T. R. Jensen, M. Karlsson, Terrence J. Udovic

Abstract

The local structure and reorientational dynamics of KB3H8 were studied using quasielastic and inelastic neutron scattering, Raman spectroscopy, first-principles calculations and differential scanning calorimetry. The results reveal the existence of a previously unknown polymorph in between the α' and β-polymorphs. Furthermore, it was found that the [B3H8] anion undergoes different reorientational motions in the three polymorphs, α, α'and β. In α-KB3H8, the [B3H8] anion performs 3-fold rotations in the plane created by the three boron atoms, which changes to a 2-fold rotation around the C2 symmetry axis of the [B3H8] anion upon transitioning to α'-KB3H8. After transitioning to β-KB3H8, the [B3H8] anion performs 4-fold rotations in the plane created by the three boron atoms, which indicates that the local structure of β-KB3H8 deviates from the global cubic NaCl type structure. The results also indicate that the high reorientational mobility of the [B3H8] anion facilitates the K+ transport, since the two-orders-of-magnitude increase in the anion reorientational mobility observed between 297 K and 311 K coincides with a large increase in K+ conductivity.
Citation
Journal of Physical Chemistry C
Volume
125
Issue
7

Keywords

B3H8- anion, fixed window scan, inelastic neutron scattering, KB3H8, neutron vibrational spectroscopy, octahydrotriborate anion, quasielastic neutron scattering, QENS, reorientational motion

Citation

Andersson, M. , Grinderslev, J. , Chen, X. , Chen, X. , Haussermann, U. , Zhou, W. , Jensen, T. , Karlsson, M. and Udovic, T. (2021), Interplay between the Reorientational Dynamics of the B<sub>3</sub>H<sub>8</sub><sup>-</sup> Anion and the Structure in KB<sub>3</sub>H<sub>8</sub>, Journal of Physical Chemistry C (Accessed June 21, 2024)

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Created February 24, 2021, Updated September 16, 2021