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

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  • M. S. Andersson, Chalmers University of Technology, National Institute of Standards and Technology, Gaithersburg
  • ,
  • J. B. Grinderslev
  • X.M. Chen, Henan Normal University, China
  • X. Chen, Henan Normal University, Zhengzhou University
  • ,
  • U. Haussermann, Stockholm University
  • ,
  • W. Zhou, National Institute of Standards and Technology, Gaithersburg
  • ,
  • T. R. Jensen
  • M. Karlsson, Chalmers University of Technology
  • ,
  • T. J. Udovic, National Institute of Standards and Technology, Gaithersburg, University of Maryland

The structure and reorientational dynamics of KB3H8 were studied by using quasielastic and inelastic neutron scattering, Raman spectroscopy, first-principles calculations, differential scanning calorimetry, and in situ synchrotron radiation powder Xray diffraction. The results reveal the existence of a previously unknown polymorph in between the -and -polymorphs. Furthermore, it was found that the [B3H8] anion undergoes different reorientational motions in the three polymorphs , , and . In -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 -KB3H8. After transitioning to -KB3H8, the [B3H8] anion performs 4-fold rotations in the plane created by the three boron atoms, which indicates that the local structure of -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+ cation conductivity, since the 2-orders-of-magnitude increase in the anion reorientational mobility observed between 297 and 311 K coincides with a large increase in K+ conductivity.

Original languageEnglish
JournalJournal of Physical Chemistry C
Pages (from-to)3716-3724
Number of pages9
Publication statusPublished - Feb 2021

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