Tables for
Volume A
Space-group symmetry
Edited by M. I. Aroyo

International Tables for Crystallography (2015). Vol. A, ch. 1.4, p. 48


H. Wondratscheke

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The structure of the Hermann–Mauguin symbols for the plane groups

The positions of the representative symmetry directions for the crystal systems are given. The lattice symbol and the maximal order of rotations around a point are followed by two positions for symmetry directions.

Crystal systemLattice(s) First positionSecond positionThird position
Oblique p   1 or 2
Rectangular p, c 1 or 2 a b
Tetragonal p 4 a ab
Hexagonal p 3 a 1
    3 1 ab
    6 a ab