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The full information on space groups is given in the International Tables for Crystallography. The basic knowledge of the space groups on the EM online book (see link) is your good start since it is necessary to know the general principles of the spacegroup designations in order to use the crystalstructure databases correctly. A table (see link) gives the list of the known 230 threeperiodic space groups and the space groups that have not been completely determined. The 230 space groups were proposed in the late 19th century independently by Fedorov[1], Barlow[2] and Schoenflies[3].
Space groups represent the ways that the macroscopic and microscopic symmetry elements (operations) can be selfconsistently arranged in space. There are totally 230 space groups. The space groups add the centering information and microscopic elements to the point groups. Figure 4547 schematically shows the relationship between the 7 crystal systems, 14 Bravais Lattices, 32 point groups, and 230 space groups. By combining the 32 point groups with the translation operations of 14 Bravais lattices, 73 symmorphic space groups are obtained. The other 157 (=23073) space groups have pointsymmetry operations with improper (partial) translations, i.e. rotations through screw axes and reflections (mirrors) in glide planes.
Figure 4547. The relationship between the 7 crystal systems, 14 Bravais Lattices, 32 point groups, and 230 space groups.
Table 4547 lists the relation between threedimensional crystal families, crystal systems, and lattice systems.
Table 4547. The relation between threedimensional crystal families, crystal systems, and lattice systems.
Crystal
family 
Crystal
system 
Required
symmetries
of point group 
Point
group 
Space
group 
Bravais
lattices 
Lattice
system 

None 
2 
2 
1 
Triclinic 

1 twofold axis of rotation or 1 mirror plane 
3

13

2

Monoclinic 
Orthorhombic 
3 twofold axes of rotation or 1 twofold axis of rotation and two mirror planes 
3 
59 
4 
Orthorhombic 
Tetragonal 
1 fourfold axis of rotation 
7 
68 
2 
Tetragonal 
Hexagonal 
Trigonal 
1 threefold axis of rotation 
5 
7 
1 
Rhombohedral 
18 
1 
Hexagonal 
Hexagonal 
1 sixfold axis of rotation 
7 
27 

4 threefold axes of rotation 
5 
36 
3 
Cubic 
Total: 6 
7 

32 
230 
14 
7 
XRD obeys Friedel's Law because it can be approximately described by kinematical scattering. This limits the number of the space groups of crystals that can be determined by XRD to fifty. For electron diffraction, multiple (dynamical) scattering of the incident electrons in the TEM specimen occurs so that the Friedel's law is broken down, and thus the crystals with all the 230 space groups can be identified.
Note that the dspacing and the intensities of the diffracted spots can be different for different crystals even though their space group are the same, for instance, as discussed in page3013 for space group Pnma (62).
[1] E.S. Fedorov (1891) ”Симмтрія правильныхъ системъ фигуръ” (“The symmetry of regular systems of figures”), Zapiski
Imperatorskogo S. Petersburgskogo Mineralogichesgo Obshchestva (Proceedings of the Imperial St. Petersburg Mineralogical Society),
2(28), pp 1146. English translation: David and Katherine Harker, (1971) “Symmetry of Crystals”, American Crystallographic Association
Monograph No. 7, Buffalo, N.Y. Am. Cryst. Ass. pp 50131.
[2] W. Barlow (1894) “Über die Geometrischen Eigenschaften homogener starrer Strukturen und ihre Anwendung auf Krystalle” (“On the geometrical properties of homogeneous rigid structures and their application to crystals”), Zeitschrift für Krystallographie und
Minerologie, 23, pp 163.
[3] A. Schoenflies (1892) Krystallsysteme und Krystallstruktur.
