ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
A neutron diffraction study of Debye-Waller factors has been performed on ThC and ThC0.77 powder samples at 4 and 250 K on the high-resolution diffractometers D1A and D1B of HFR (Grenoble); 25 diffraction lines were resolved and analysed with wavelength λ = 1.21 Å on D 1A, and 22 lines with λ = 1.28 Å on D1B. In the case of ThC, it is shown that the results (BTh = 0.07 ± 0.05 Å2 and BC = 0.40 ± 0.08 Å2 at 4 K; BTh = 0.32 ± 0.08 Å2 and BC = 0.68 ± 0.08 Å2 at 250 K) are mainly due to the thermal vibrations. For ThC0.77, we find BTh = 0.23 ± 0.03 Å2 and BC = 0.47 ± 0.05 Å2 at 4 K, and BTh = 0.48 ± 0.04 Å2 and BC = 0.69 ± 0.05 Å2 at 250 K. The enhancements of the Debye-Waller factors compared to the stoichiometric case are attributed to the static distortions induced by the presence of 23% vacancies in the carbon sublattice. The mean-square static displacements of thorium and carbon atoms are found to be about 1% of the lattice parameter \sqrt{\langle \Delta x^{2}\rangle _{\rm Th} = 0.08 ± 0.03 Å and \sqrt{\langle \Delta x^{2}\rangle _{\rm c}\simeq _{\rm Th} 0.05 ± 0.03 Å.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S056773948000191X
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