X-ray powder diffraction studies and bond-valence analysis of Hg2Sb2O7

The crystal structure of Hg2Sb2O7 has been refined using X-ray powder diffraction technique. Hg2Sb2O7 crystallizes in the cubic pyrochlore structure type, space group Fd (3) over barm, with the lattice parameter a = 10.3525(5) angstrom, Z= 8, D, = 9.060(1) g/cm(3). The Rietveld refinement procedure was stopped when the intensity residual R-B = 3.25% had been reached. In the bond-valence analysis of the crystal structure of Hg2Sb2O7, the values of the bond-valence parameters reported for the Sb5+/O2- ion pair have been found to be doubtful. Using the new calculation scheme, the improved bond-valence parameters for the Sb5+/O2- ion pair (r(0) = 1.908 angstrom and b = 0.409 angstrom) have been derived from the crystal structure of Sb2O5. (C) 2007 Elsevier B.V. All rights reserved.