BiOn coordination polyhedrons in crystal structures

The Voronoi-Dirichlet polyhedrons (VDPs) and the method of intersecting sph eres were used to analyze the oxygen environment of the Bi(III) and Bi(V) a toms in the crystal structures of 173 compounds. The VDP volume of Bi(III) decreases with an increase in its coordination number. A quantitative estim ate is given for the stereo effect exerted by the electron lone pair of Bi( III). It accounts for the asymmetry of the Bi(III) coordination sphere and manifests itself as a substantial displacement [on the average, by 0.3(1) A ngstrom] of the Bi(III) atom from the center of gravity of its VDP.