STRUCTURE OF BAGAF5-CENTER-DOT-2H(2)O FROM CONVENTIONAL AND SYNCHROTRON POWDER DIFFRACTION DATA

The compound BaGaF5 . 2H(2)O was prepared at moderate temperature, 60- 80 degrees C, from HF aqueous solution. It crystallizes in the monocli nic system, space group P2(1)/m with a = 10.0626(6) Angstrom, b = 5.80 70(1) Angstrom, c = 4.9788(3) Angstrom, beta = 103.359(7)degrees and Z = 2. The structure was determined from conventional powder diffractio n data by direct methods and refined from synchrotron data to R-P = 10 .8 and R-B = 4.0 % by the Rietveld method using a program modified to account for anisotropic line broadening. The bidimensional structure i s built up from layers of isolated [GaF5(H2O)] octahedra interconnecte d by [BaF11(H2O)] cuboctahedra.