Acta Crystallographica Section B

Structural Science

Volume 55, Part 2 (April 1999)

research papers

Acta Cryst. (1999). B55, 139-146 [ doi:10.1107/S0108768198010805 ]

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

V. A. Blatov, L. V. Pogildyakova and V. N. Serezhkin

Abstract: About 2100 inorganic and organometallic compounds containing beryllium, magnesium and alkaline earth atoms (M) were investigated with Voronoi-Dirichlet polyhedra (VDPs). It is shown that the coordination numbers (CNs) of the M atoms in MO_n coordination polyhedra can be determined by means of VDPs without 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 monomodal for the other alkaline earth metals. Beryllium and magnesium coordination polyhedra containing weak M-O contacts were classified by variants of their 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 $\ge$ 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.