ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The controversial space-group problem of spinel, MgAl2O4, whether it is Fd3m or F{\bar 4}3m, was studied by electron diffraction. It was confirmed that the appearance of 'forbidden reflections' such as {200} was caused by the double reflection process of reflections with high indices on the non-zero-order Laue zone. Consequently, the space group of spinel is Fd3m, and the assignment of the space group to F{\bar 4}3m is ruled out. The change of space group from F{\bar 4}3m to Fd3m associated with a phase transition, proposed by Mishra & Thomas [Acta Cryst. (1977), A33, 678], can also be explained by double diffraction: the magnitudes of primary reflections with high indices rapidly decrease due to the increase of the Debye-Waller factors at elevated temperatures.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739480000198
