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Figure 6
Tilted octahedra and basal parallelogram planes, e.g. PQRS, of AX12 polyhedra (in yellow) viewed along the orthorhombic z axis in space group Pbnm. The + and – signs in black denote z heights of the octahedral vertices relative to the z = 0 plane of the diagram. These are due to [{a^ - }] tilting. Green dashed lines show the directions of pseudocubic axes xPC and yPC, the reference directions for the [{a^ - }] tilting. Red dotted lines represent the perpendicular planes to the green dashed lines, which are projected as lines in the xy plane. Red circles lie above the red dotted lines at the same z height as the octahedral vertices O a to O d. They are denoted by O a′ to O d′ and result from the four projections (O a → O a′), (O b → O b′), (O c → O c′) and (O d → O d′). c+ tilting causes the octahedra to be rotated about the orthorhombic z axis (or equivalently, the zPC axis). The relevant tilt angles, ϕc,1 and ϕc,2, are shaded orange. (Vectors p and q are defined in §2.6[link].)

Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206
Volume 78| Part 1| February 2022| Pages 40-60
https://doi.org/10.1107/S2052520621012713
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