Order–disorder transition in monoclinic sulfur: a precise structural study by high-resolution neutron powder diffraction

The order–disorder phase transition in monoclinic β-sulfur has been characterized using high-resolution neutron powder diffraction. The transition is critical and continuous, with a transition temperature, T_c = 198.4 (3) K, and a critical exponent, β = 0.28 (3), which is indicative of three-dimensional ordering.

Structure of strontium barium niobate Sr_xBa_1 − xNb₂O₆ (SBN) in the composition range 0.32 ≤ x ≤ 0.82

The structure of strontium barium niobate crystals is studied in the whole range of the tetragonal tungsten bronze phase using X-ray diffraction measurements. Unit-cell parameters, density, site-occupancy factors and interionic distances show pronounced composition dependencies which are explained by model calculations.

Electron-diffraction structure refinement of Ni₄Ti₃ precipitates in Ni₅₂Ti₄₈

The crystal structure of Ni₄Ti₃ precipitates was refined by means of quantitative electron diffraction in combination with density functional theory. Application of the multi-slice least-squares (MLSL) method made the refinement possible.

The crystal structure of Zr₂NiD_4.5

The fully ordered crystal structure of Zr₂NiD_4.5 has been determined by combined synchrotron-radiation powder diffraction, electron diffraction and powder neutron diffraction.

On the crystal structure of Cr₂N precipitates in high-nitrogen austenitic stainless steel. III. Neutron diffraction study on the ordered Cr₂N superstructure

The neutron diffraction study on the ordered Cr₂N superstructure has been carried out. The occupancies of the N atoms in four crystallographic sites were determined, and the deviations of the metal atoms from their ideal positions are also specified. The ideal and measured crystal structures of Cr₂N are compared.

On the compression mechanism of FeF₃

The compression mechanism of FeF₃ has been studied by time-of-flight neutron powder diffraction. No structural phase transitions were observed, but a small octahedral strain was found to develop during compression which reflects an elongation of the FeF₆ octahedra along the c axis.

A bibliometric study in crystallography

Bibliometric studies based on data from the Inorganic Crystal Structure Database were performed with a focus on growth rates and distribution of publications, productivity of authors and multiple authorship.

Atomic and domain structure of the low-temperature phase of barium metagermanate (BaGeO₃)

The crystal structure, stacking faults and twinning of the low-temperature form of barium metagermanate are described using X-ray powder diffraction and electron microscopy.

Analysis of migration paths in fast-ion conductors with Voronoi–Dirichlet partition

A general algorithm to analyze voids in crystal structures was developed and implemented into the computer package TOPOS. This approach was used to predict the positions of Li⁺ and Na⁺ cations and to analyze their possible migration paths in the solid superionic materials Li₃M₂P₃O₁₂ (M = Sc, Fe; LIPHOS) and Na_1 + xZr₂Si_xP_3 − xO₁₂ (NASICON)

Structural characterization of a new high-pressure phase of GaAsO₄

Ab initio crystal structure determination of a new high-pressure high-temperature phase of GaAsO₄ from powder data. This new hexagonal phase contains fragments of the rutile-like structure and represents the preceding high-pressure step before the stabilization of the rutile structure.

Theoretical determination of the structures of CaSiO₃ perovskites

The crystal structures of several possible low-temperature polymorphs of CaSiO₃ perovskites, and their evolution with pressure, are determined from first-principles calculations.

Superspace-symmetry determination and multi­dimensional refinement of the incommensurately modulated structure of natural fresnoite

The five-dimensional incommensurately modulated structure of a natural fresnoite crystal has been solved and refined from X-ray single-crystal diffraction data at 110 K in terms of superspace representation.

A new simplifying approach to molecular geometry description: the vectorial bond-valence model

A vectorial interpretation of the bond-valence concept is proposed to adequately describe coordination geometry in metal complexes which involve multidentate ligands. Representation of the latter by a single such vector often leads to the direct applicability of the valence-shell electron-pair repulsion model.

Growth-induced incommensurability observed in the organic co-crystal hexa­methylene­tetramine resorcinol

The structure of the co-crystal hexamethylenetetramine resorcinol is incommensurately modulated at room temperature. The structure is noteworthy for the simultaneous presence of disorder and occupational modulation.

Structural characterization of p-benzosemi­quinone radical in a solid state: the radical stabilization by a low-barrier hydrogen bond

The radical p-benzosemiquinone was detected in the solid state by X-ray structure analysis and EPR spectroscopy. A low-barrier O—H⋯O hydrogen bond stabilizes the radical. The two polymorphs of p-benzosemiquinone were observed and their structures solved.

Hydrophobic `lock and key' recognition of N-4-nitro­benzoylamino acid by strychnine

The hydrophobic recognition of N-4-nitrobenzoyl-D- or N-4-nitrobenzoyl-L-amino acids at the surface of strychnine self-assemblies causes the resulting surface to have more hydrophilic properties, which are more appropriate for interactions in the hydrophilic environments from which the strychnine salts were investigated.

Pressure-frozen 1,2,3-tri­chloro­propane

The pressure-frozen structure of 1,2,3-trichloropropane, C₃H₅Cl₃, has been determined by single-crystal X-ray diffraction at 0.28 and 0.35 GPa, and the intermolecular electrostatic, halogen⋯halogen and halogen⋯H crystal cohesion forces have been related to the crystal morphology and compressibility.

Competing hydrogen-bonding patterns and phase transitions of 1,2-di­amino­ethane at varied temperature and pressure

The crystal structures of three new high-pressure phases of 1,2-diaminoethane have been determined, and transformation between the four known phases of 1,2-diaminoethane has been rationalized by revealing the competing patterns of NH⋯N hydrogen bonding.

Molecular interactions in crystalline di­bromo­methane and di­iodo­methane, and the stabilities of their high-pressure and low-temperature phases

Pressure-frozen CH₂Br₂ at 0.61 GPa forms C2/c crystals, while CH₂I₂ crystallizes at 0.16 GPa in the polar space group Fmm2. Transformations between C2/c and Fmm2 structures of CH₂I₂ at varied temperature and intermolecular electrostatic halogen⋯halogen and H⋯halogen crystal cohesion forces have been analysed.

Effect of pressure on the crystal structure of salicylaldoxime-I, and the structure of salicylaldoxime-II at 5.93 GPa

The crystal structure of salicylaldoxime has been determined at room temperature at pressures from 0.75 to 5.28 GPa. Salicylaldoxime forms a pseudo-macrocycle which contains a cavity which decreases in size with pressure. Above 5.28 GPa the structure transforms to a new polymorph, the structure of which has been determined at 5.93 GPa. The changes in intermolecular interactions during the phase transition are interpreted with the aid of PIXEL calculations.

Interplay between steric and electronic factors in determining the strength of intramolecular N—H⋯O resonance-assisted hydrogen bonds in β-enaminones

The crystal structures of five β-enaminones, forming strong intramolecular N—H⋯O resonance-assisted hydrogen bonds, have been determined at 150 K. These structures were compared with those of other similar compounds in order to discover which steric and electronic factors are important in the formation of very strong hydrogen bonds.

Structures of mono-unsaturated tri­acylglycerols. I. The β₁ polymorph

The crystal structures of the β₁ polymorphs of mono-unsaturated triacylglycerols and of the isomorphous β-VI cocoa butter have been solved from high-resolution powder diffraction data. This complicated but successful structure solution has led to a new model for the published β₂ (β-V) structure.

Structures of mono-unsaturated tri­acylglycerols. II. The β₂ polymorph

An improved crystal structure model has been established for the β₂ polymorph of mono-unsaturated triacylglycerols and the isomorphous β-V structure of cocoa butter. For the first time two asymmetric β₂ polymorphs are reported and the fat-bloom mechanism of chocolate is explained.