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Guide to the k-vector figures

The Brillouin zones are two-dimensional objects in the reciprocal space. The coordinate axes are designated by k_x and k_y, and the origin with coefficients (0,0) always concides with the centre of the Brillouin zone and is called Γ (indicated as GM in the k-vector tables). In the Brillouin-zone figures, the representation domains of L&W are compared with the asymmetric units of ITA. A statement of whether the representation domain of L&W and the asymmetric unit are identical or not is given below the k-vector table. The asymmetric units are often not fully contained in the Brillouin zone, but protrude from it, in particular by flagpoles (for a discussion of flagpoles description the reader is referred to [3]).

The representatives of the orbits of k-vector symmetry points or of symmetry lines, as well as the edges of the representation domains of L&W and of the asymmetric units are brought out in colours.

1. Symmetry points: A representative point of each orbit of special k-vector points is designated by circle filled in red with its label also in red. Note that a point is coloured red only if it is really a special point, i. e. a point whose layer little co-group is a supergroup of the little co-groups of the points in its neighbourhood. A point is marked by its label and an empty circle if it is listed in the correspondig k-vector table but is not a point of special symmetry.
   
   
2. Symmetry lines: A line is coloured in red with its label also in red only if it is a special k-vector line, i.e. the layer little co-groups of the points on the line are supergroups of the little co-groups of the points in its neighbourhood. The colour of the line is pink for an edge of the asymmetric unit which is not a symmetry line. The colour of the line is brown with the name in red for a line which is a symmetry line as well as and edge of the asymmetric unit. The edges of the representation domains are coloured light blue if the representation domain of L&W does not coincide with the asymmetric unit. Edges of the representation domain and their labels are coloured dark-blue if they are symmetry lines. Flagpoles are always coloured in red. Coordinate axes, edges of the Brillouin zone or auxiliary lines are displayed by thin solid black lines.