Incommensurate structure of InAl_1 − xTi_xO_3 + x/2 [x = 0.701 (1)]: comparison between modulated and composite models

The monoclinic phase of the compound InAl_1 − xTi_xO_3 + x/2 with x = 0.701 (1) has been studied through single-crystal X-ray diffraction.

Incommensurate structure of Ca₂Al₂O₅ at high temperatures – structure investigation and Raman spectroscopy

A high-temperature X-ray diffraction study revealed that brownmillerite-type Ca₂Al₂O₅ transforms to an incommensurately modulated structure at elevated temperatures. The characterization is completed by Raman spectroscopy.

Inorganic structures in space group P3m1; coordinate analysis and systematic prediction of new ferroelectrics

Twelve families with the space group P3m1 are shown to satisfy the structural criteria for, and hence may be predicted to exhibit, the property of ferroelectricity. Sixteen other families are likely to be nonpolar with a similar number having reduced predictive properties.

Order, disorder and structural modulations in Bi–Fe–W–O–Br Sillén–Aurivillius intergrowths

A new Sillén–Aurivillius intergrowth Bi₄Fe_1/3W_2/3O₈Br has been studied by transmission electron microscopy and associated techniques, along with its structural evolution when heated at high temperature (1473 K).

Special features of intermolecular bonding A⋯D (A = Si, Ge and D = nucleophile) in crystal structures

Crystal structure analysis of silicon- and germanium-containing compounds within the framework of the stereoatomic model was carried out to distinguish the quantitative descriptors of the intermolecular contacts Si⋯D and Ge⋯D.

X-ray diffuse scattering from HMTA: analysis via a Monte Carlo model

The occupancy and displacive short-range order in HMTA, the adduct of hexamethylenetetramine and azelaic acid, have been examined using X-ray diffuse scattering, determining the ordering of molecular flips and the key intermolecular interactions.

High-pressure structural study of L-α-glutamine and the use of Hirshfeld surfaces and graph-set notation to investigate the hydrogen bonding present in the structure up to 4.9 GPa

The following article explores the effect of high pressure on the L-α-glutamine crystal structure. Results show that the main structural feature to be influenced by pressure is the hydrogen bond network.

Pressure-freezing with conformational conversion of 3-aminopropan-1-ol molecules

3-Aminopropan-1-ol molecules change their conformation from a pseudo-ring in the vapour and liquid to an extended one in the solid state, and the intramolecular hydrogen bonds are replaced with intermolecular ones. The liquid freezes at 0.1 MPa/284 K and at 0.13 GPa/296 K in the same polar monoclinic structure, space group Cc.

Conformational richness and multiple Z′ in salt co-crystal of N-methylpiperidine betaine with N-methylpiperidine betaine hexa­fluorosilicate

The crystal structure of a 4:1 complex between N-methylpiperidine betaine (N-carboxymethyl-N-methylpiperidinium inner salt) and hexafluorosilicic acid reveals six different dimers of hemiprotonated betaine molecules, formed via very short O⋯H⋯O hydrogen bonds between the carboxylic functions.

Interaction geometries and energies of hydrogen bonds to C=O and C=S acceptors: a comparative study

It is shown that hydrogen bonds from O—H and N—H donors to the S acceptors of thioureas and thioamides are relatively longer (by ∼ 0.25 Å) and weaker (by ∼ 12 kJ mol⁻¹) than hydrogen bonds to the analogous O-acceptor compounds.

Role of the gauche effect and local 1,3-dipole–dipole interactions in stabilizing an unusual conformation of tartarodi­nitriles

X-ray and NMR studies of meso and chiral tartarodinitriles reveal their diverse conformational preferences compared with tartrates and NH-tartramides, and point to the gauche effects, local dipolar and strong intermolecular interactions as structure determining factors.

Hydrogen-bond motifs in the crystals of hydrophobic amino acids

A new computer program to search for hydrogen-bond motifs has been developed and used to identify frequent ring and chain motifs in amino-acid crystal structures.

On the correlations between the polyhedron eccentricity parameters and the bond-valence sums for the cations with one lone electron pair

The applicability of the Wang–Liebau polyhedron eccentricity parameter in the bond-valence model has been found to be doubtful: the correlations between the values of the polyhedron eccentricity parameters and the bond-valence sums calculated for the cations with one lone electron pair are probably an artifact of the poorly determined bond-valence parameters.

Charge-density studies of energetic materials: CL-20 and FOX-7. Corrigendum

A corrigendum to the paper by Meents et al. (2008), Acta Cryst. B64, 42–49.