International
Tables for
Crystallography
Volume E
Subperiodic groups
Edited by V. Kopský and D. B. Litvin

© International Union of Crystallography 2006
International Tables for Crystallography (2006). Vol. E. ch. 1.2, p. 14   | 1 | 2 |

Section 1.2.8.2. Rod groups

V. Kopskýa and D. B. Litvinb*

a Department of Physics, University of the South Pacific, Suva, Fiji, and Institute of Physics, The Academy of Sciences of the Czech Republic, Na Slovance 2, PO Box 24, 180 40 Prague 8, Czech Republic, and bDepartment of Physics, Penn State Berks Campus, The Pennsylvania State University, PO Box 7009, Reading, PA 19610-6009, USA
Correspondence e-mail:  u3c@psu.edu

1.2.8.2. Rod groups

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For all rod groups, a limit is set on the z coordinate of the asymmetric unit by the inequality[0\leq z\leq\hbox{ upper limit on }z.]For each of the x and y coordinates, either there is no limit and nothing further is written, or there is the lower limit of zero.

For tetragonal, trigonal and hexagonal rod groups, additional limits are required to define the asymmetric unit. These limits are given by additional inequalities, such as [x\leq y] and [y\leq x/2]. Fig. 1.2.8.1[link] schematically shows the boundaries represented by such inequalities.

[Figure 1.2.8.1]

Figure 1.2.8.1 | top | pdf |

Boundaries used to define the asymmetric unit for (a) tetragonal rod groups and (b) trigonal and hexagonal rod groups.

Example: The rod group [{\scr p}6_3mc] (R70)

[\displaylines{\quad{\bf Asymmetric}\,\,{\bf unit}\quad 0\leq x;\,0\leq y;\,0\leq z\leq 1;\,y\leq x/2.\hfill}]








































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