AB-INITIO STRUCTURE DETERMINATION OF ZR(OH)2SO4.3H2O USING CONVENTIONAL MONOCHROMATIC X-RAY-POWDER DIFFRACTION

The structure of Zr(OH)2SO4.3H2O has been determined ab initio by conventional powder diffractometry using monochromatic X-rays. The pattern was indexed using the successive-dichotomy method yielding cell dimensions a = 8.3645(4), b = 15.1694(9), c = 5.4427(3)angstrom and beta = 103.145(5)-degrees. The space group is P2(1)/c with Z = 2. 519 integrated intensities were extracted by whole-pattern fitting and these were used to calculate the heavy-atom positions by the Patterson method. Successive Fourier syntheses located the nine 0 atoms. Rietveld refinement was carried out over an angular range of 15 to 135-degrees(20) and this converged with R(F) = 0.030, R(B) = 0.066, R(p) = 0.085 and R(wp) = 0.109. The structure consists of zig-zag chains in the direction of [001] formed by edge-sharing eightfold-coordinated zirconium polyhedra in the shape of a bicapped trigonal prism. Sulfate tetrahedra bridge within chains whilst a network of hydrogen bonding stabilizes interchain interactions to form 'corrugated sheets' parallel to the (100) plane; between these sheets lie 'free' water molecules that do not take part in the polyhedra but do play a major role in the hydrogen-bonding network. The ICDD Powder Diffraction File No. is 44-1493.