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

Published

February 25, 2021

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

Pub Type

Journals

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 B₃H₈^- Anion and the Structure in KB₃H₈, Journal of Physical Chemistry C (Accessed October 27, 2025)