Neutron diffraction study of Sr(BrO₃)₂·H₂O:statistical tests of intensity variances, refinement including weak and negative intensities

Abstract

Sr(Br0 3 ) 2 · H 2 0, M r = 361.478, monoclinic, ΓΖ/c (conventional C2/c), a = 887.0(1), b = 761.1(1), c = 936.9(1) pm, β = 91.82(1)°, V = 0.6321 nm 3 , Ζ = 4, D x = 3.80 g cm -3 , λ (neutron) = 87.013 pm, μ = 0.0055 mm" 1 , F(000) = 215.0 fm, Τ = 297 Κ, R = 0.063, wR = 0.046, S 2 = 1.48 (0.04), 1592 unique intensities, 58 parameters, refinement on \F\ 2 including weak and negative intensities. The intensities are checked for normal and independent distribution and for proper choice of their variances. A simple formula is applied to take weakening by extinction into account. The results are in agreement with X-ray data confirming the distinct anisotropy of the thermal ellipsoid of the water oxygen. The OH bond length is 93.9(1) pm, the HOH angle 112.9(1)°, the hydrogen bond length (H...O) 187.5(1) pm. * Fachgebiet Strukturforschung, Fachbereich Materialwissenschaft der TH Darmstadt, Außenstelle in KFA/ZFR.