Neutron diffraction study of β–MnSO3 · 3 D2O anharmonic motion of oxygen and hydrogen, statistical tests of intensity variances, refinement including weak and negative intensities

Abstract

Abstract β–MnSO3 · 3 D2O, Mr = 195.078, orthorhombic, P212121, a = 9.7668(12) Å, b = 5.6373(7) Å, c = 9.5598(10) Å, V = 526.3 Å3, Z = 4, Dx = 2.46 g cm−3 λ (neutron) = 0.87013 Å, μ = 0.060 cm−1, F(000) = 296 fm, T = 297 K, R = 0.07, wR = 0.024, S 2 = 1.07 (0.04), 6303 measured, 1348 unique intensities, 229 refined parameters, refinement on |F|2 including weak and negative intensities. The intensities are shown to be normally and independently distributed and their variances to be properly determined. A simple model is applied to take weakening by extinction into account. Anharmonic motion of two O and two D atoms up to the fourth order of a Gram-Charlier expansion was refined. One of these two O forms very long hydrogen bonds (3.02 Å–3.16 Å).