Evidence of a Transition to Reorientational Disorder in the Cubic Alkali-metal Dodecahydro-closo-dodecaborates

Published

November 1, 2011

Author(s)

Kristina Verdal, Hui Wu, Terrence J. Udovic, Vitalie Stavila, Wei Zhou, John J. Rush

Abstract

A neutron powder diffraction (NPD) and differential scanning calorimetry(DSC) study indicates that Cs₂B₁₂H₁₂ undergoes a second-order phase transition near 529 K that can be described as a reorientational disordering of the B₁₂H₂^2- icosahedral anions between two lowest-energy configurations within the cubic strucutre. Such a disordering requires the addition of another mirror plane to the low-temperature Fm3 structural symmetry to become Fm3{i}m. Additional DSC measurements of the lighter alkali-metal cubic isomorphs. Rb₂B₁₂H₁₂ and K₂B₁₂H₁₂, also indicate second-order transitions for these compounds near 742 K and 811 K, respectively. These results are suggestive of similar order-disorder phase changes as for Cs₂B₁₂H₁₂, although confirmation of their existence requires analogous diffraction measurements.

Citation

Journal of Physics and Chemistry of Solids

Volume

184

Pub Type

Journals

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Keywords

B12H12, dodecaborate, neutron powder diffraction, phase transition, reorientational disorder

Citation

, K. , Wu, H. , Udovic, T. , Stavila, V. , Zhou, W. and Kasianowicz, J. (2011), Evidence of a Transition to Reorientational Disorder in the Cubic Alkali-metal Dodecahydro-closo-dodecaborates, Journal of Physics and Chemistry of Solids, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908798 (Accessed December 9, 2024)