Analysis of the environment of beryllium, magnesium and alkaline earth atoms in oxygen-containing compounds

About 2100 inorganic and organometallic compounds containing beryllium, mag nesium and alkaline earth atoms (M) were investigated with Voronoi-Dirichle t polyhedra (VDPs). It is shown that the coordination numbers (CNs) of the M atoms in MOn coordination polyhedra can be determined by means of VDPs wi thout crystal-chemical radii. The distributions of the M-O distances in the coordination spheres of the M atoms are bimodal for M = Be or Mg and monom odal for the other alkaline earth metals. Beryllium and magnesium coordinat ion polyhedra containing weak M-O contacts were classified by variants of t heir distortions. It is found that the volume of the domains of the Mg, Ca, Sr and Ba atoms is independent of their CNs at CN greater than or equal to 6 (up to 16 for barium). The possibility of using the model of deformable spheres to describe the crystal structure of the compounds investigated is suggested.