The molecular coordination numbers (MCN) in crystal structure of polymorphic modifications of simple substances were calculated and the predominance of MCN = 14 was found by means of Voronoi-Dirichlet polyhedra (VDP). The obtained values were compared with MCNs, determined by the van der Waals radii (WR). It was shown that the features of topology of the environment of a molecule could be discovered during the analysis of VDP for its center of gravity. Among such VDPs the Fedorov cuboctahedron is the most frequent that conforms the arrangement of molecular centers of gravity on the b.c.c. lattice. The variation of characteristics of interatomic contacts in structures of polymorphic modifications of selenium, tellurium and oxygen at increased pressure was studied.