Disorder in Ag₇GeSe₅I, a superionic conductor: temperature-dependent anharmonic structural study

A temperature-dependent structural investigation of the substituted argyrodite Ag₇GeSe₅I has been carried out on a single crystal from 15 K up to 475 K in steps of 50 K. The results of that study have been correlated with the crystal's conductivity properties.

Capabilities and limitations of a (3 + d)-dimensional incommensurately modulated structure as a model for the derivation of an extended family of compounds: example of the scheelite-like structures

A (3 + d)-dimensional incommensurately modulated structure can be exploited as a natural superspace model for the generation, prediction and description of a (3 + d)-dimensional family consisting of both three-dimensional and (3 + d)-dimensional members. The capabilities and limitations of an incommensurately modulated structure to act as a natural superspace model for the generation of a family are illustrated with an example of the scheelite-like compound derived from the (3 + 1)-dimensional incommensurately modulated KNd(MoO₄)₂ structure.

Structures of the cubic and rhombohedral high-pressure modifications of silicon as packing of the rod-like substructures determined by the algebraic geometry

Structures of the high-pressure phases BC8 and R8 of silicon are described as parallel rod packings, where rods are stacks of flattened icosahedra. The mechanism of the transformation between these modifications is described as the rotation of a common triangular face between two neighboring icosahedra.

Crystal chemistry of mimetite, Pb₁₀(AsO₄)₆Cl_1.48O_0.26, and finnemanite, Pb₁₀(AsO₃)₆Cl₂

Synthetic samples of the neutral apatite mimetite, Pb₁₀(AsO₄)₆(Cl_2 − xO_x/2), and its reduced form finnemanite, Pb₁₀(AsO₃)₆Cl₂, have been structurally characterized using a combination of neutron diffraction, transmission electron microscopy and X-ray diffraction spectroscopy. Both materials conform to hexagonal P6₃/m symmetry; however, the average mimetite structure is best described through the introduction of partially occupied oxygen sites.

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

A detailed charge-density study of the two energetic materials CL-20 and FOX-7 is presented.

Statistical survey of hydrogen-bond motifs in crystallographic special symmetry positions, and the influence of chirality of molecules in the crystal on the formation of hydrogen-bond ring motifs

The probabilities that hydrogen-bond ring motifs (synthons) will occupy various crystallographic special symmetry positions, as well as the effect of chirality of molecules in the crystal on the probability of formation of hydrogen-bond ring motifs, are examined. The results show that the inversion center has a significant effect on the formation of hydrogen-bond ring motifs.

Configurational and conformational classification of pyranose sugars

Cluster analysis has been applied to pyranose sugars found in the Cambridge Structural Database.

Using small molecule crystal structure data to obtain information about sulfonamide conformation

Relative energies of conformations of acyclic sulfonamide structures in the solid state are estimated from the Cambridge Structural Database using cluster analysis, and the effect of this group on adjacent torsion angles studied.

Structural comparisons of isomeric series of 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines

Six new structures of benzopyrazolo[3,4-b]quinolines are reported, and structural comparisons are made both within the two series, of 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines, respectively, now numbering 14 structures in total, and between isomeric pairs of compounds from these two series.

Patterns of hydrogen bonding in mono- and di-substituted N-arylpyrazinecarboxamides

In N-arylpyrazinecarboxamides, the molecules may be linked into supramolecular structures in zero, one or two dimensions by various combinations of hydrogen bonds, augmented by π⋯π stacking interactions. Within isomeric series the dimensionality of the supramolecular aggregation appears to be very sensitive to both the identity and the location of the substituent on the N-aryl ring.

Accurate molecular structures of chloro­thiazide and hydro­chloro­thiazide by joint refinement against powder neutron and X-ray diffraction data

The compounds chlorothiazide and hydrochlorothiazide (crystalline form II) have been studied in their fully hydrogenous forms by neutron powder diffraction on the GEM diffractometer. The results of joint Rietveld refinement of the structures against multi-bank neutron and single-bank X-ray powder data are reported.

Effects of fluoro substitution on 4-bromodi­phenyl ether (PBDE 3)

Using X-ray structure analysis, electron-density determinations by ¹³C chemical shifts and semi-empirical calculations we have investigated the structural characteristics of fluorine-tagged polybrominated diphenylethers (PBDEs). Fluorine tagging is a useful tool to provide information about the conformation of the PBDEs. This approach will provide valuable information about the potential biological activities and toxicities of these pollutants.

Predicting regularities in lattice constants of GdFeO₃-type perovskites

This work correlates the lattice constant of GdFeO₈-type perovskites with the ionic radii of the cations using genetic programming. The resultant prediction models of the lattice constant are in the form of mathematical expressions.

The Periodic Table: Its Story and Its Significance

Notes for authors 2008