ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The RED extinction model reported previously [Kulda (1987). Acta Cryst. A43, 167-173] was applied to several neutron diffraction data sets, some of them already used in the design of the Cooper & Rouse [Acta Cryst. (1971), A27, 622-628] empirical extinction formula and in the tests of the Becker & Coppens [Acta Cryst. (1974), A30, 129-147] formalism. The results of least-squares refinements fully confirm the expected gain in agreement due to an improved description of the coherent part of the wave interaction by the RED model, whose adequacy is further supported by the realistic values of the refined effective deformation gradient and mean free path between subsequent reflections. The RED-based harmonic thermal vibration parameters are systematically somewhat larger than those obtained within the Becker & Coppens formalism and follow more closely the expected quasi-harmonic temperature dependence. Significant differences are also found between the two models in terms of the derived room-temperature Debye-Waller parameters. The RED values BSr = 0.557 (10) × 10-2 and BF = 0.830 (10) × 10-2 nm2 agree better with the results of shell model calculations based on experimental phonon dispersion curves.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767387011942
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