ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The results of the investigation of the choice of origins in the description of space groups [Burzlaff & Zimmermann (1980). Z. Kristallogr. 153, 151-179] can be used to give group-theoretical reasons for the classification of cubic space groups by the aid of Archimedean truncated octahedron as was proposed by Chieh [Acta Cryst. (1979), A35, 946-952]. The division into units is independent of the choice of origin; however, it is found to be advantageous to place the centers of the geometric units at proper or privileged origins in dealing with cubic space groups without the site of cubic point-group symmetry, so as to simplify description of the geometric units. A modification is proposed in the representations of geometric-unit sequences. If the new symbols for the sequences of geometric units are extended by the symmetry of the centers of the units, there is a one-to-one correspondence between these extended sequence symbols and the non-isomorphic space group. Moreover, the extension of this concept to orthorhombic space groups with 'cubic' affine normalizers may be useful.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S056773948200151X
