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- Title
Thermal Polymorphism in CsCB 11 H 12.
- Authors
Černý, Radovan; Brighi, Matteo; Wu, Hui; Zhou, Wei; Dimitrievska, Mirjana; Murgia, Fabrizio; Gulino, Valerio; de Jongh, Petra E.; Trump, Benjamin A.; Udovic, Terrence J.
- Abstract
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 I 4 3d polymorph near 353 K and (ii) a disordered Fm 3 polymorph that initially appears from the disordered I 4 3d 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.
- Subjects
IONIC conductivity; AB-initio calculations; QUASI-elastic scattering; X-ray powder diffraction; NEUTRON spectroscopy; NEUTRON scattering
- Publication
Molecules, 2023, Vol 28, Issue 5, p2296
- ISSN
1420-3049
- Publication type
Article
- DOI
10.3390/molecules28052296