Structure refinement of trigonal zinc-chlorine boracite, Zn3B7O13Cl, from single-crystal and powder X-ray diffraction

Abstract Abstract Zn3B7O13Cl: R3c, a hex = 8.53725(7) Å, c hex = 20.96849(25) Å. V hex = 1323.53(3) Å,3 a rh = 8.5527(1) Å, αrh = 59.8809(1)°, Dx = 3.8931Mg/m3, Rp = 0.081 and RB = 0.047 for 35 reflections and 44 parameters from powder profile refinement (T = 298 K); R = 0.051 for 1568 reflections and 74 parameters from single-crystal refinement (T = 298 K). A comparison with isostructural iron-chlorine boracite, Fe3B7O13Cl, suggests that the magnitude of the rhombohedral lattice shear in trigonal boracites depends in a complex manner on the bonding requirement of the five-coordinate metal ions, and the space requirement of an oxygen-boron framework that is relatively rigid with respect to changes of O—B bondlengths and O—O contact distances, but more flexible with respect to changes of bond angles and torsion angles. Key Words: Boracite X-ray diffraction structure