Disorder in crystals of dioxo­fluorotungstates, (NH₄)₂WO₂F₄ and Rb₂WO₂F₄

Orientational disorder in Rb₂WO₂F₄ and (NH₄)₂WO₂F₄ have been compared. In the ammonium compound, but not in the rubidium compound, it was possible to distinguish between O and F atoms in the distorted cis-[WO₂F₄]₂ octahedron and to determine its true geometry owing to the dynamic nature of the disorder. The ammonium compound undergoes phase transitions of the order–disorder type when the temperature is lowered but the rubidium compound does not.

Isosymmetrical phase transition in α-YbV₄O₈

The mixed-valence vanadate α-YbV₄O₈ undergoes an isosymmetrical phase transition at 70 K. The transition is accompanied by a paramagnetic–paramagnetic anomaly and leads to complete charge ordering.

Structural behaviour of synthetic Co₂SiO₄ at low temperatures

The crystal structure of the synthetic cobalt olivine, Co₂SiO₄, is determined by means of single-crystal neutron diffraction and X-ray powder diffraction in the temperature range 300–2.5 K.

Order–disorder character and twinning in the structure of a new synthetic titanosilicate: (Ba,Sr)₄Ti₆Si₄O₂₄·H₂O

The ordered P2/c structure of (Ba,Sr)₄Ti₆Si₄O₂₄·H₂O was obtained first by solving the disordered Cmmm structure by single-crystal X-ray diffraction data and then applying the order–disorder theory.

Original disorder–order transition related to electronic and magnetic properties in the thermoelectric misfit phase [Ca₂CoO₃][CoO₂]_1.62

A structural phase transition is shown around 400 K for the thermoelectric lamellar misfit cobalt oxide [Ca₂CoO₃][CoO₂]_1.62. This transition is related to a rearrangement of the central [CoO] layer of the [Ca₂CoO₃] slab.

Modular crystals as modulated structures: the case of the lillianite homologous series

The use of the superspace formalism is extended to the analysis and refinement of homologous series of modular structures, with two symmetry-related modules. This approach has been successfully applied to the lillianite homologous series.

Formability of ABX₃ (X = F, Cl, Br, I) halide perovskites

A total of 186 complex halide systems were collected; the formabilities of ABX₃ (X = F, Cl, Br and I) halide perovskites were investigated using the empirical structure map, which was constructed by Goldschmidt's tolerance factor and the octahedral factor.

Structural characterization of RE₁₀W₂₂O₈₁ rare-earth tungstates (RE = Ce, Nd)

The single-crystal X-ray diffraction study of Ce₁₀W₂₂O₈₁ and powder X-ray diffraction experiments on Ce₁₀W₂₂O₈₁ and Nd₁₀W₂₂O₈₁ show that the true space group of these phases is Pbnm.

Synchrotron powder diffraction characterization of the zeolite-based (p-N,N-di­methylnitroaniline–mordenite) guest–host phase

The crystal structure of mordenite zeolite hosting guest molecules of p-N,N-dimethylnitroaniline has been solved by synchrotron powder diffraction. The localization of the molecules in the channel system and the possible stabilizing interactions are discussed and compared with literature results.

The elusive [Ni(H₂O)₂(15-crown-5)]²⁺ cation and related co-crystals of nickel(II) hydrates and 15-crown-5

The yellow compound [Ni(H₂O)₂(15C5)](NO₃)₂, 15C5 = 15-crown-5, has been made by heating pale green crystals of [Ni(H₂O)₆](NO₃)₂·15C5·2H₂O to over 350 K. While trying to obtain the Ni²⁺ ion inside the crown ligand five other compounds were prepared, all of which have surprisingly complicated crystal structures organized by the hydrogen-bonded motif ⋯15C5⋯H₂O—Ni^II—OH₂⋯15C5⋯H₂O—Ni^II—OH₂⋯.

Five more phases of the structural family [M(H₂O)₂(15-crown-5)](NO₃)₂

Structures of five more phases of the [M(H₂O)₂(15-crown-5)](NO₃)₂ (M = Mg, Mn, Fe, Co, Ni, Cu and Zn) family have been determined. All stable phases whose existence at accessible temperatures is indicated by differential scannng calorimetry have now been characterized.

Improvement of anisotropic displacement parameters from invariom-model refinements for three L-hydroxylysine structures

Three L-hydroxylysine structures have been determined at 100 K by single-crystal X-ray diffraction to high resolution using a laboratory or synchrotron source. Visualizations of anisotropic displacement parameter (ADP) differences with the program PEANUT indicate the high quality of the invariom ADPs, which are similar to ADPs from a free multipole refinement and superior to ADPs from IAM and high-order IAM refinements.

Bitter sweeteners: tetrazole derivatives of arylsulfonylalcanoids – synthesis, structure and comparative study

The crystal structures of four derivatives of arylsulfonylalkanoids obtained in the course of the syntheses of new artificial sweeteners have been determined and compared with other tetrazole-containing structures identified from a CSD search. The lack of a sweet taste of the four tetrazole derivatives is tentatively explained.

Structures of mono-unsaturated tri­acylglycerols. V. The β′₁-2, β′-3 and β₂-3 polymorphs of 1,3-dilauroyl-2-oleoylglycerol (LaOLa) from synchrotron and laboratory powder diffraction data

The polymorphism of 1,3-dilauroyl-2-oleoylglycerol has been studied and the structures of the -2, β′-3 and β₂-3 polymorphs have been solved from high-resolution powder diffraction data.

Chiral carboxylic acids and their effects on melting-point behaviour in co-crystals with isonicotinamide

The crystal structures of co-crystals of two systems of chiral carboxylic acids, optically active and racemic 2-phenylpropionic acid and 2-phenylbutyric acid, with isonicotinamide are reported to investigate the effects of the chirality of the chiral carboxylic acids on the melting point of the co-crystal complexes.

Polymorphism in cyclo­hexanol. Corrigendum

A corrigendum to the paper by Ibberson et al. (2008), Acta Cryst. B64, 573–582.