Hydrothermal synthesis and structure of the ordered modification of Pb7F12Br2

We recently discovered a disordered and ordered modification of a compound with composition Ba7F12Cl2. Both modifications of the lead compound, Pb7F12 Cl2, can be obtained from a flux (disordered, space group (P6(3)/m) or by h ydrothermal growth (ordered, space group P (6) over bar)). Needle shaped cr ystals of the title compound, Pb7F12Br2, were found to form during hydrothe rmal synthesis. The structure was refined in the hexagonal space group P (6 ) over bar to R = 0.028 for 829 reflections and 45 parameters. Lattice para meters an a = b = 1035.6(2) pm and c = 402.24(8) pm with Z = 1. (C) 2000 Ed itions scientifiques et medicales Elsevier SAS. All rights reserved.