Full international symbols of crystallographic space groups

2 Full international symbols of crystallographic space groups 

The crystal structure was solved using a non-standard setting, since most of the modem crystallographic software enables minor deviations from the standard, and the results were published as they were obtained, without converting to a conventional orientation. It is worth noting that many, but not all technical journals allow certain deviations fi om crystallographic standards. 

The crystal structure contains some specific molecules, blocks, layers, or chains of atoms or molecules, which may be easily visualized or represented using space group symmetry in a non-standard setting. 

Deviations from the standard are most often observed in the monoclinic crystal system, because there are many different ways that result in a nonstandard setting in this crystal system. This uncertainty is even reflected in the International Tables for Crystallography, where there are two different settings in the monoclinic crystal system. When the unique two-fold axis is parallel to b (i.e. to T-axis), this setting is considered a standard choice, but when it is parallel to c (or to Z-axis), this is an allowed alternative setting. In addition, the unique two-fold axis can be chosen to be parallel to a (i.e. to X-axis), which is considered a non-standard setting. 

one of the most commonly observed in both natural and synthetic crystals, space group symmetry P2)/c (standard notation with the unique two-fold screw axis parallel to Y, and a = y = 90° and p 90°) can be listed as follows  

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