The dynamic symmetry and its application for interpretation of X-ray diffraction patterns

It is shown here that real crystals besides their crystallographic symmetry (230 space groups) display another kind of symmetry called in this paper — the dynamic symmetry (1651 Shubnikov groups). The dynamic symmetry manifests itself during transformation by the crystal structure of quantities whose symmetry has two-color operations.An example is given of application of dynamic symmetry for interpretation of phenomenon of forbidden reflexions in an X-ray pattern of ethylidene-N, N′-diacetamide crystals.