STRUCTURE DETERMINATION OF BA(OD)BR.2D2O BY NEUTRON POWDER DIFFRACTION

Barium hydroxide bromide dihydrate (d-5), Ba(OD)Br.2D2O, M(r) = 275.32, tetragonal, P4/nmm, Z = 2, neutron radiation, lambda = 1.09 angstrom, mu-calc = 0.065 cm-1, F(000) = 126.62 fm, [(sin-theta)/lambda]max = 0.632 angstrom-1, T1 = 300 K, a = 4.5825 (4), c = 11.791 (2) angstrom, V = 247.60 (3) angstrom 3, D(x) = 3.693 Mg m-3, R(profile) = 0.0208; T2 = 16 K, a = 4.5567 (2), c = 11.718 (1) angstrom, V = 243.30 (1) angstrom 3, D(x) = 3.758 Mg m-3, R(profile) = 0.0209. The structure is related to the PbFCl type with ninefold coordination of the Ba atoms. The OD- ions are not coordinated to the Ba atoms, but are acceptors of four very strong hydrogen bonds. The OD distances are 0.992 (5) [0.994 (4)] angstrom for D2O, 0.956 (13) [0.951 (9)] angstrom for OD- and 1.639 (5) [1.622 (4)] angstrom for DOD...OD-.