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Figure 7
Schematic representation of the stacking rule, in symbolic figures representation; projection along the c vector (Kupčík's cell). OD layers (L0, L1) are perpendicular to the projection plane. The figures corresponding to structural units in z = ¼ are in black, those in z = ¾ (closer to the observer) are in red. The locations of σ-POs [. a2 .] , [. 2½ .], [[\bar 1]] are indicated. The t(1, ¼, 0) translation is obvious from the positions of symbolic figures of adjacent layers. Note that the σ-POs indicated are related to the initial three-dimensional objects (combinations of two prisms), and symbolic figures are their projections, corresponding to Fig. 5[link](c). The objects have faces oriented to the observer (visible) and from the observer (invisible, at the opposite side). For instance, [. 2½ .] maps the empty lower triangular faces of the leftmost pattern of L0 oriented to the observer (visible side) onto the empty upper triangles on the leftmost black-and-white pattern of L1 at the invisible side of the pattern (behind the full triangle).

Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206
Volume 69| Part 6| October 2013| Pages 570-583
doi:10.1107/S2052519213024238
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