NEUTRON-DIFFRACTION STUDY OF BETA-MNSO3-CENTER-DOT-3 D2O ANHARMONIC MOTION OF OXYGEN AND HYDROGEN, STATISTICAL TESTS OF INTENSITY VARIANCES, REFINEMENT INCLUDING WEAK AND NEGATIVE INTENSITIES

beta-MnSO3 . 3 D2O, M(r) = 195.078, orthorhombic, P2(1)2(1)2(1), a = 9 .7668(12) Angstrom, b = 5.6373(7) Angstrom, c = 9.5598(10) Angstrom, V = 526.3 Angstrom(3), Z = 4, D-x = 2.46 g cm(-3) lambda (neutron) = 0. 87013 Angstrom, mu = 0.060 cm(-1), F(000) = 296 fm, T = 297 K, R = 0.0 7, wR = 0.024, S-2 = 1.07 (0.04), 6303 measured, 1348 unique intensiti es, 229 refined parameters, refinement on \F\(2) including weak and ne gative intensities. The intensities are shown to be normally and indep endently 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 lo ng hydrogen bonds (3.02 Angstrom - 3.16 Angstrom).