The CaWO4 structure has been refined, starting with the parameters of Sillén and Nylander, using two zones of neutron diffraction data. The oxygen coordinates with the origin of the cell at the W atom (4̄) are x=0.2413 (σ=0.0005), y=0.1511 (σ=0.0006), z=0.0861 (σ=0.0001). The slightly distorted WO4 tetrahedron contains a W–O distance of 1.788 Å (σ=0.003) and angles of 113° 27′ (σ=14′) and 107° 56′ (σ=0.09′). Close nonbonded approaches are Ca–O=2.48 Å and O–O=2.77 Å. Anisotropic thermal vibration parameters were also determined.
The hydrogen positions in the crystal structure of copper formate tetrahydrate have been determined, and some new data on the antiferroelectric phase transition at −38.9°C are presented. It is shown that the orientation of the water molecules is disordered in such a way as to permit all possible short 0–0 contacts to be hydrogen bonded all of the time. The disorder is similar to that observed in ice. The phase transition probably occurs because of hydrogen motion.
Three zones of neutron diffraction data were obtained for Mn(HCO2)2.2HzO and the positions of the hydrogen atoms determined. The hydrogen bonding scheme proposed by Osaki, Nakai and Watanabe was found to be correct. The crystal structure of copper formate dihydrate was rerefined by means of the method of least squares. Some changes in bond distances were noted.
The antiferromagnetic structure of anhydrous cupric sulfate, C11SO4, has been determined from neutrondiffraction powder data and by use of the single-crystal susceptibility results of Kreines. A least-squares refinement of the crystal structure was also carried out in order to obtain a good absolute scale factor for the neutron analysis. The original x-ray data of Kokkoros and Rentzeperis were used in these calculations. The magnetic structure is collinear, with -\
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