Molecular coordination numbers and crystal structure of simple substances

The molecular coordination numbers (MCN) in crystal structure of polymorphi c modifications of simple substances were calculated and the predominance o f MCN = 14 was found by means of Voronoi-Dirichlet polyhedra (VDP). The obt ained 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 m olecule could be discovered during the analysis of VDP for its center of gr avity. Among such VDPs the Fedorov cuboctahedron is the most frequent that conforms the arrangement of molecular centers of gravity on the b.c.c. latt ice. The variation of characteristics of interatomic contacts in structures of polymorphic modifications of selenium, tellurium and oxygen at increase d pressure was studied. (C) 1999 Elsevier Science B.V. All rights reserved.