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

Crystallographic face forms {hkl} are interpreted as sets of symmetry-equivalent X-ray reflections. Extending an earlier paper on twinning by merohedry [Σ = 1, Klapper & Hahn (2010). Acta Cryst. A66, 327–346], the eigensymmetry of these forms is used to derive general relations between the diffraction intensities of overlapping twin-related reflections. The following twins by reticular merohedry are treated: Σ3 twins of rhombohedral and cubic, Σ5 twins of tetragonal and Σ7 twins of hexagonal crystals.