Module: xrd.spacegroup¶
Interface with sglite for hkl generation and Laue group determination
This module contains mappings from space group number to either Hall or Hermann-Mauguin notation, as well as the inverse notations.
Space groups can be mapped to crystal class (one of 32 point groups) and then to crystal system .
NOTES:
- Laue group is the cyrstal class if you add a center of symmetry. There are 11 Laue groups, determined directly from the point group.
- This module avoids the use of numpy and uses math module instead. That means the hkl lists are not numpy arrays, but simple lists of tuples.
- Rhombohedral lattices:
REFERENCES
1. Mappings among space group number, Hall symbols and Hermann-Mauguin symbols. http://cci.lbl.gov/sginfo/hall_symbols.html
- For mapping space group number to point group (crystal class in Schonflies notation)
http://en.wikipedia.org/wiki/Space_group
- Crystallography and crystal defects By Anthony Kelly, G. W. Groves, P. Kidd
4. Contains point group from sgnum. http://en.wikipedia.org/wiki/Space_group#Classification_systems_for_space_groups
5. Point group to laue group http://www.ruppweb.org/Xray/tutorial/32point.htm
6. For discussion of rhombohedral lattice and “obverse” and “reverse” settings for lattice parameters. Crystal structure determination (book) By Werner Massa
TESTING
Run this module as main to generate all space groups and test the HKL evaluation.
1 Class¶
- class hexrd.xrd.spacegroup.SpaceGroup(sgnum)[source]¶
Bases: object
Wrapper on sglite
- __init__(sgnum)[source]¶
Constructor for SpaceGroup
INPUTS sgnum – (int) space group number (between 1 and 230)
- getHKLs(ssmax)[source]¶
Return a list of HKLs with a cutoff sum of square
INPUTS ssmax – cutoff sum of squares
OUTPUTS hkls – a list of all HKLs with sum of squares less than
or equal to the cutoff, excluding systematic absences and symmetrically equivalent hklsDESCRIPTION
- latticeType[source]¶
Lattice type
Possible values are ‘cubic’, ‘hexagonal’, ‘trigonal’, ‘tetragonal’, ‘orthorhombic’, ‘monoclinic’ and ‘triclinic’
Rhombohedral lattices are treated as trigonal using the “obverse” setting.
- sgnum¶
Space group number
- sixLatticeParams(lparams)[source]¶
Return the complete set of six lattice parameters from the abbreviated set
INPUTS lparams – (tuple) the abbreviated set of lattice parameters
OUTPUTS sparams – (tuple) the complete set of lattice parameters;
(a, b, c, alpha, beta, gamma)DESCRIPTION * Output angles are in degrees