On the structure of aragonite

The structure of geological aragonite was revised using high-resolution X-ray diffraction on synchrotron beamline. The data obtained unambiguously confirm that pure aragonite crystals have orthorhombic symmetry.

On the structure of lithium peroxide, Li₂O₂

On the basis of space-group reanalysis and high-quality DFT calculations, a new, refined crystal structure for lithium peroxide, Li₂O₂, is proposed. Energetic arguments help to question the validity of one of the two previously reported structures, accepted since 1953.

On the crystal structure of Cr₂N precipitates in high-nitrogen austenitic stainless steel

The crystal structure of Cr₂N precipitates was confirmed to be trigonal and was characterized by three sets of superlattice reflections. The occupation probability function describing the distribution of nitrogen was derived based on the superlattice reflections obtained in SAD patterns.

Incommensurate crystallographic shear structure of Ba_xBi_2 − 2xTi_4 − xO_{11 − 4x} (x = 0.275)

A new incommensurate structure of Ba_xBi_2 − 2xTi_4 − xO_{11 − 4x} (x = 0.275) has been determined. The aperiodic insertion of domain boundaries by the crystallographic shear (CS) operation is defined by the four-dimensional formalism.

Structure and microstructure of hexagonal Ba₃Ti₂RuO₉ by electron diffraction and microscopy

The crystal structure and microstructure of the hexagonal perovskite Ba₃Ti₂RuO₉ have been refined using convergent-beam electron diffraction and high-resolution electron microscopy.

Structure of toluene6.4-ZSM-5 and the toluene disproportionation reaction on ZSM-5

We have investigated the structure of toluene6.4-ZSM-5 by X-ray single-crystal diffraction and have shown the toluene disproportionation reaction on ZSM-5 zeolite.

Three differently coloured concomitant polymorphs: synthesis, structure and packing analysis of (4-(3′,5′-di­methyl-1H-pyrazol-1′-yl)-6-methyl-2-phenylpyrimidine)di­chlorocopper(II)

A method of estimating the efficiency of π–π stacking using the Voronoi–Dirichlet partition of crystal space was demonstrated using three polymorphs of the novel compound (4-(3′,5′-dimethyl-1H-pyrazol-1′-yl)-6-methyl-2-phenylpyrimidine)dichlorocopper(II).

Packing and molecular shape: layers of centred hexagons as a guiding principle

From the 112 993 structures containing one residue per cell approximately a third form a packing which may be described as composed of stacks of layers of centred hexagons. The probability of this kind of packing and the density of packing are correlated with the shape of the second moment ellipsoids (ellipsoids of moments of inertia) of the respective molecules.

Structure determination of the stable anhydrous phase of α-lactose from X-ray powder diffraction

The crystal structure of the stable anhydrous form of α-lactose is solved ab initio at room temperature from X-ray powder diffraction patterns and the minimization of crystalline energy. The Monte-Carlo simulated annealing method is used, followed by Rietveld refinements with geometric soft restraints on bond lengths and bond angles.

Structural characterization of [1,4]diazepino[6,5-b]indoles by powder diffraction

The crystal structures of six [1,4]diazepino[6,5-b]indole derivatives and three intermediates have been determined and characterized using laboratory X-ray powder diffraction data.

Determination of the low-temperature structure of hexa­methylbenzene

The structure of hexamethylbenzene below the first-order phase transition at 117 K has been obtained using neutron powder diffraction, over 70 years after the first report of the room-temperature X-ray crystal structure of this ubiquitous laboratory chemical. The low-temperature structure may be considered as a high-density modification of the room-temperature structure, resulting from decreased thermally induced disorder.

Inclusion compounds of plant growth regulators in cyclodextrins. V. 4-Chloro­phenoxyacetic acid encapsulated in β-cyclodextrin and hepta­kis­(2,3,6-tri-O-methyl)-β-cyclodextrin

The X-ray crystal structure analyses of two crystals of 4-chlorophenoxyacetic acid encapsulated in β-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin was reported. It is the fifth part of a series concerning the inclusion compounds of plant growth regulators in cyclodextrins.

A helical structure with Z′ = 10

A very unusual high Z′ structure with no important crystallographic pseudosymmetry has been determined.

Isomeric N-(iodo­phenyl)nitrophthalimides: interplay of C—H⋯O hydrogen bonds, iodo⋯nitro and iodo⋯carbonyl interactions, and aromatic π⋯π stacking interactions

Five isomeric N-(iodophenyl)-nitrophthalimides all exhibit a different range of intermolecular interactions, including C—H⋯O(nitro) and C—H⋯O(carbonyl) hydrogen bonds, two- and three-centre iodo⋯nitro and two-centre iodo⋯carbonyl interactions, and aromatic π⋯π stacking interactions; all five isomers have qualitatively different supramolecular structures.