InternationalSpace-group symmetryTables for Crystallography Volume A Edited by M. I. Aroyo © International Union of Crystallography 2015 |
International Tables for Crystallography (2015). Vol. A, ch. 1.4, pp. 47-48
## Section 1.4.1.4.7.1. Trigonal space groups H. Wondratschek
^{e} |

Trigonal space groups are characterized by threefold rotation or screw rotation or rotoinversion axes in [001]. There may be in addition 2 and 2_{1} axes in [100] or , but only in one of these two directions. The same holds for reflections *m* or glide reflections *c*. The different possibilities are: