The application of eigensymmetries of face forms to X-ray diffraction intensities of crystals twinned by `reticular merohedry'

Klapper, H.; Hahn, Th.

doi:10.1107/S0108767311032454

Figure 7
Ditetragonal (bi)-pyramid {12l}_ditetr, a combination of subforms{12l}_tetr (shaded) and {21l}_tetr (white). Subset {12l}_tetr is mapped upon itself by the [Sigma]

5 twin elements (diffraction case A, cf. Fig. 6

), whereas subset {21l}_tetr has no twin-related coinciding counterpart and is `single' (`partial coincidence').