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Figure 4
(Left) Part of the 2e orbit ([{1\over 4} 0 z], [{3\over 4} 0 \overline z]) of a space group of type Pmma (No. 51, standard setting) and (right) its projection on the (001) plane. The height (z coordinate) is shown as + and −, as is customary in ITA7. No chirality (`comma') is shown on the atoms because the site-symmetry group of Wyckoff position 2e is mm2. The hatched area on the left-hand side of the figure is the unit cell shifted by a/4 on an atom, to emphasize that the orbit has the same translation vectors as the space group (i.e. it is not an extraordinary orbit). The right-hand side of the figure, obtained by projection so that all the atoms appear on the plane and no distinction by height appears, shows that in this projection the additional translation vector [{1 \over 2} 0 0] appears, so that the unit cell seems to be halved along the a axis.

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 48| Part 4| August 2015| Pages 1290-1298
https://doi.org/10.1107/S1600576715011206
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