Structure of Ga₂O₃(ZnO)₆: a member of the homologous series Ga₂O₃(ZnO)_m

The structure of Ga₂O₃(ZnO)₆ is clarified using single-crystal X-ray diffraction techniques, and general rules for constructing structures in the homologous series Ga₂O₃(ZnO)_m are presented.

Orientational disorder and phase transitions in crystals of (NH₄)₂NbOF₅

Structural phase transitions in a crystal of (NH₄)₂NbOF₅ are the consequence of dynamic changes in its structural units as the temperature decreases. Using X-ray diffraction, it is possible to identify O and F atoms in the disordered structure of (NH₄)₂NbOF₅ as a result of its dynamic nature.

5d and 4f electron configuration of CeB₆ at 340 and 535 K

The electron-density distribution of CeB₆ was measured at 340 and 535 K to determine the electron configuration of 4f and 5d orbitals, and the electron transfer from B to Ce.

[Rh(C₇H₈)(PPh₃)Cl]: an experimental charge-density study

An accurate experimental charge-density analysis is reported for the title compound, in order to gain further insights into the bonding situation in rhodium complexes. Particular focus is given to examining the interactions between the rhodium metal centre and the norbornadiene cage.

From six- to five-coordinated Sb^III in [(CH₃)₃PH]₃[Sb₂Cl₉]: transition pathways from single-crystal X-ray diffraction

[(CH₃)₃PH]₃[Sb₂Cl₉] experiences four phase transitions which were found by means of calorimetry, thermogravimetry and X-ray diffraction. The crystal structure was solved in the space group P6₃/mmc at 382 K (phase I), Pnam at 295 K (phase II) and Pna2₁ at 175 K (phase V).

Redetermination of the structure and dielectric properties of bis­(thiourea) pyridinium iodide – a new ferroelectric inclusion compound

The structures of three phases of the inclusion compound bis(thiourea) pyridinium iodide have been determined. Ferroelectric properties have been found in the low-temperature phases.

Polymorphism in cyclo­hexanol

The crystal structures of phase II and the metastable phases III′ and III of cyclohexanol, C₆H₁₁OH, have been determined using high-resolution neutron powder and single-crystal X-ray diffraction techniques. Phase II crystallizes in a tetragonal structure, space group , characterized by a hydrogen-bonded tetrameric ring motif. Phases III′ and III are monoclinic, space groups P2₁/c and Pc, respectively, with molecules linked via hydrogen-bonded chains.

Hydrogen-bond patterns and the structures of 1,4-cyclo­hexanediol: 2:1 cis:trans-1,4-cyclo­hexanediol

Two determinations of the structure of trans/cis co-crystals of 1,4-cyclohexanediol are reported, and their intermolecular hydrogen-bond patterns described using the graph-set model.

Orientational ordering in the low-temperature stable phases of deuterated thiophene

A structural investigation of thiophene between 155 and 1.5 K by neutron diffraction is reported.

N⁶-Substituted 2-amino-4-chloro-5-formylpyrimidines: puckered versus planar pyrimidine rings, and hydrogen-bonded aggregation in zero, one, two and three dimensions

In N⁶-substituted 2-amino-4-chloro-5-formylpyrimidines, with three adjacent substituents on the pyrimidine ring, this ring can be planar or else puckered towards boat, screw-boat or twist-boat conformations. The supramolecular aggregation is dominated by N—H⋯N hydrogen bonds and the resulting hydrogen-bonded structures can be finite (zero-dimensional) or one-, two- or three-dimensional.

Anhydrous versus hydrated N⁴-substituted 1H-pyrazolo[3,4-d]pyrimidine-4,6-di­amines: hydrogen bonding in two and three dimensions

N⁴-substituted 1H-pyrazolo[3,4-d]pyrimidine-4,6-diamines can crystallize either in anhydrous form or as stoichiometric hemihydrates or monohydrates, and the hydrogen-bonded structures they form may be either two- or three-dimensional. Those examples which crystallize as hemihydrates adopt very similar supramolecular structures despite a wide diversity of N⁴-substituents and space groups.

Polymorphism of urea–barbituric acid co-crystals

The existence of different polymorphs for urea and barbituric acid co-crystals is explained on the basis of the resonance properties of barbituric acid (mesomeric effect). Higher-level graph-set analysis revealed a specific behaviour of the hydrogen-bond systems responsible for the mutual spatial arrangement of the structural components in the polymorphs.

A room-temperature X-ray diffuse scattering study of form (II) of the trimorphic molecular system p-(N-methylbenzyl­idene)-p-methylaniline

Strong and highly structured diffuse scattering has been observed for form (II) of the trimorphic molecular system p-(N-methylbenzylidene)-p-methylaniline. Analysis using Monte Carlo simulation techniques has revealed highly correlated molecular motions, suggesting possible mechanisms for the transformation to the other polymorphs.

Crystallography of Modular Materials. Vol. 15, IUCr Monographs on Crystallography