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Published in:
2012 | OriginalPaper | Chapter
8. The Seven Crystal Systems
Author : Dr. Walter Borchardt-Ott
Published in: Crystallography
Publisher: Springer Berlin Heidelberg
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Abstract
This definition distinguishes six crystal systems. It is, however, usual to separate the system of crystallographic axes based on a = b ≠ c, α = β = 90°, γ = 120° into a hexagonal and a trigonal crystal system.
In Table 8.1, the seven crystal systems are listed along with the restrictions on the axial system. It is important to remember, however, that equivalence of crystallographic axes and special values of the angles are simply a consequence of the underlying symmetry. Those symmetry elements which cause equivalences to arise between crystallographic axes are listed. A full list of the symmetry elements characterizing the various crystal systems is given in Table 9.9.
The space groups of the lattices themselves have the highest symmetry which can occur in that crystal system (cf. Table 7.4.).