NEUTRON POWDER DIFFRACTION STUDY OF THE SCINTILLATOR MATERIAL ZNWO4

With a view to the technological applications of ZnWO4 crystals, we ha ve performed Rietveld profile refinement of medium-resolution, time-of -flight, neutron powder diffraction data of synthetic ZnWO4 to improve the quality of the current crystal structure derived from single crys tal X-ray techniques that produced a final solution with an R factor o f only 10%. The new structural data for ZnWO4, monoclinic space group P2/c, lattice parameters of 0.469263(5), 0.572129(7), 0.492805(5) nm f or a, b and c respectively, and a beta angle of 90.6321(9)degrees with two formula units per unit cell. The ZnO6 octahedra contain 3 pairs o f Zn-O bonds of 0.2026(2), 0.2090(2) and 0.2227(3) nm and the WO6 octa hedra contain 3 pairs of W-O bonds 0.1789(2), 0.1914(2) and 0.21331(3) nm. These new data confirm the basic structure of ZnWO4 and provide a ccurate off-centring magnitudes for the Zn and W cations.