PREPARATION AND CRYSTAL-STRUCTURE OF CSBO2

Colourless single crystals of CsBO2 have been prepared from intimate mixtures of CsO0.57 and B2O3 (Cs:B = 3.2:1.0; 600 degrees C, 38 d). The structure determination from four-circle diffractometer data (MoK<(alpha)over bar>, 443 I-o (h k l), R = 3.1%, R(w) = 2.0%) confirms the isotypy with NaBO2 and KBO2: space group R (3) over bar c; a = 1363.7(2) pm, c = 836.5(2) pm; Z = 18. A characteristic structure unit is the planar cyclic anion [B3O6](3-). Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radii (MEFIR), the Madelung Part of Lattice Energy (MAPLE) and the Charge Distribution (CHARDI) are calculated and discussed.