Scientific article
Open access

Thermal Polymorphism in CsCB11H12

Published inMolecules, vol. 28, no. 5, 2296
Publication date2023-03-01
First online date2023-03-01

Thermal polymorphism in the alkali-metal salts incorporating the icosohedral monocarba-hydridoborate anion, CB11H12−, results in intriguing dynamical properties leading to superionic conductivity for the lightest alkali-metal analogues, LiCB11H12 and NaCB11H12. As such, these two have been the focus of most recent CB11H12− related studies, with less attention paid to the heavier alkali-metal salts, such as CsCB11H12. Nonetheless, it is of fundamental importance to compare the nature of the structural arrangements and interactions across the entire alkali-metal series. Thermal polymorphism in CsCB11H12 was investigated using a combination of techniques: X-ray powder diffraction; differential scanning calorimetry; Raman, infrared, and neutron spectroscopies; and ab initio calculations. The unexpected temperature-dependent structural behavior of anhydrous CsCB11H12 can be potentially justified assuming the existence of two polymorphs with similar free energies at room temperature: (i) a previously reported, ordered R3 polymorph stabilized upon drying and transforming first to R3c symmetry near 313 K and then to a similarly packed but disordered I43d polymorph near 353 K and (ii) a disordered Fm3 polymorph that initially appears from the disordered I43d polymorph near 513 K along with another disordered high-temperature P63mc polymorph. Quasielastic neutron scattering results indicate that the CB11H12− anions in the disordered phase at 560 K are undergoing isotropic rotational diffusion, with a jump correlation frequency [1.19(9) × 1011 s−1] in line with those for the lighter-metal analogues.

  • Anion dynamics
  • Crystal structure
  • Monocarba-hydridoborate
  • Polymorphism
  • University of Geneva - [DQMP]
  • US National Science Foundation - [Agreement No. DMR-1508249]
  • US DOE - [Contract No. DE-AC02-06CH11357]
  • US DOE Office of Energy Efficiency and Renewable Energy - [Contract No. DE-AC36-08GO28308]
  • European Commission - Sustainable Materials for development of Advanced Renewable Technologies for the next generation solar CELLs [101022257]
Citation (ISO format)
CERNY, Radovan et al. Thermal Polymorphism in CsCB<sub>11</sub>H<sub>12</sub>. In: Molecules, 2023, vol. 28, n° 5, p. 2296. doi: 10.3390/molecules28052296
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Article (Published version)
ISSN of the journal1420-3049

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