THE INFLUENCE OF THE SYMMETRY OF MOLECULES ON THEIR ARRANGEMENT IN CRYSTALS

It is shown that though the natural symmetry of a molecule (i.e., the symmetry of an isolated molecule) is usually lost in the space group o f a crystal, with the exception of the inversion center, it is, as a r ule, partially or completely retained in the groups of pseudosymmetry of some molecular agglomerates (chains, layers, spatial substructures) or even of the whole structure. Thus, this symmetry influences substa ntially the packing of molecules. This influence was studied for the t hree organic crystal structures; the variety of the pseudosymmetrical molecular agglomerates that occurred in them was examined. The formati on of the latter can be successfully interpreted with the help of the method of potential functions symmetry (MPFS). The energy aspect of th e formation of pseudosymmetrical agglomerates is considered qualitativ ely.