Table 2.1.3.4

International
Tables for
Crystallography
Volume F
Crystallography of biological macromolecules
Edited by M. G. Rossmann and E. Arnold

pdf | chapter contents | chapter index | related articles

International Tables for Crystallography (2006). Vol. F. ch. 2.1, p. 52

J. Drenth^a ^*

^a Laboratory of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
Correspondence e-mail: j.drenth@chem.rug.nl

Table 2.1.3.4 | top | pdf |
The seven crystal systems

Crystal system	Conditions imposed on cell geometry	Minimum point-group symmetry
Triclinic	None	1
Monoclinic	Unique axis b: $[\alpha = \gamma = 90^{\circ}]$	2
Orthorhombic	$[\alpha = \beta = \gamma = 90^{\circ}]$	222
Tetragonal	$[a = b\semi\, \alpha = \beta = \gamma = 90^{\circ}]$	4
Trigonal	Hexagonal axes: $[a = b\semi \,\alpha = \beta = 90^{\circ}\semi\,\gamma = 120^{\circ}]$	3
	Rhombohedral axes: $[a = b = c\semi\,\alpha = \beta = \gamma]$ ^†
Hexagonal	$[a = b\semi\,\alpha = \beta = 90^{\circ}\semi\,\gamma = 120^{\circ}]$	6
Cubic	$[a = b = c\semi\,\alpha = \beta = \gamma = 90^{\circ}]$	23

^† A rhombohedral unit cell can be regarded as a cube extended or compressed along the body diagonal (the threefold axis) (see Fig. 2.1.3.2).