Theoretical structures of crystalline benzene. VI. Global search in the bisystemic structural class

A systematic search for the optical packings of benzene was made under the assumption of a bisystemic structural class that permits independent rotations of two molecules. It was found that the energy calculation correctly reproduces the symmetry and geometrical characteristics of the experimentally observed and hypothetical structures that were previously calculated within the framework of monosystemic classes. Moreover, the calculation reveals truly bisystemic hypothetical structures in which pairs of molecules that are not related by the operations of Fedorov symmetry exist. These structures are metastable with respect to the experimentally observed structures. The effect of symmetry restrictions on the conclusion of local stability of the calculated structures were studied. The derivation of the asymmetrical region of space of the structural parameters taking into account the invariant properties of the space group (affine normalizer), the molecular symmetry, and transpositions of the independent molecules was examined