Structural refinement of delithiated LiVO2 by neutron diffraction

Lithium has been extracted from the layered compound LiVO₂ by chemical oxidation with bromine. Previous X-ray data have shown that in Li_1−xVO₂ lithium extraction beyond x ≈ 0.33 is accompanied by migration of one-third of the vanadium ions into the lithium-deficient layer to stabilize the structure; little information about the location of the lithium ions could be gathered from this data. The neutron diffraction data presented in this paper show that at a composition Li_0.22VO₂, determined by atomic absorption spectroscopy, the residual lithium ions are distributed over the octahedral sites of the original lithium layer; the possibility that a small fraction of the lithium ions partially occupy the tetrahedral sites in this layer cannot be discounted. No significant occupation by lithium of the tetrahedral or octahedral vacancies in the vanadium-rich layer could be detected.     

A new crystal phase of barium nitroprusside trihydrate studied by neutron diffraction at 20 K

The crystal of barium penta­cyano­nitro­syl­ferrate trihydrate {barium nitro­prusside trihydrate, Ba[Fe(CN)₅(NO)]·3H₂O} has been studied by neutron diffraction at 20 K. The study was performed to characterize the structural phase generated by the phase transition undergone by the crystals at 80 K, at which temperature the unit‐cell volume doubles. This crystal phase still exists at 20 K. The crystal structure, in space group P1, is completely ordered. The positional changes of the water mol­ecules in the present structure with respect to those of the compound at 105 K are presented.     

A single‐crystal neutron diffraction study of RbTiOAsO4

A rubidium titanyl arsenate single‐crystal has been studied by neutron diffraction (λ = 1.207 Å). The polished sample used was 5 × 3 × 2 mm and was cut from a crystal made by top‐seeded solution growth. The crystal showed severe extinction. It was, however, possible to obtain a structural model with well defined oxy­gen sites and reasonable anisotropic displacement parameters.     

Comparative study by single crystal X-ray structure determinations of tetramethylaminoborane and tetramethylethene at 110 K

The single crystal structures of the two isoelectronic and isosteric compounds tetramethylaminoborane and tetramethylethene have been determined by an X-ray study at 110 K. The distances of the central bonds are refined to 140.3(1) pm (B=N) and 134.8(1) pm (C=C), the CXXC-torsion angles (XX=CC, BN) are smaller than 1° in both compounds. A bond-length-bond-order correlation for the aminoboranes [(CH₃)₂N] _n B(CH₃)_3–n withn=1, 2, and 3 give a regression coefficient of 0.9977, the same is found for the CNC-angle as a function of the CBNC-torsion angle. Also, the comparison among these aminoboranes show that the variation of CBNC-torsion angles has more influence on bond lengths at small angles.     

Powder neutron diffraction of SrNbO2N at room temperature and 1.5 K

The structure of strontium niobium dioxygen nitride, SrNbO₂N, has been solved by powder neutron diffraction at room temperature and 1.5 K. SrNbO₂N crystallizes in the tetragonal space group I4/mcm, with a = 5.7056 (4) and c = 8.1002 (9) Å at room temperature, and a = 5.6938 (4) and c = 8.0974 (8) Å at 1.5 K. The crystal structure is derived from the cubic perovskite archetype by a slight rotation of the Nb(O,N)₆ octahedra with respect to the tetragonal axis. A partially ordered distribution of oxygen and nitrogen on the anionic sites was found.