Incommensurate modulation of calcium barium niobate (CBN28 and Ce:CBN28)

The occupancy of the largest cation site in incompletely filled tetragonal tungsten bronze type CBN28 (calcium barium niobate) is modulated. The occupational modulation is coupled with a modulation of the atomic displacement parameters. The surrounding O atoms are displacively modulated so that the corner-sharing NbO₆ octahedra are tilted.

On the structural relations of malachite. I. The rosasite and ludwigite structure families

The crystal structures of malachite and rosasite are shown to have a common hypothetical aristotype, which is in turn closely related to the ludwigite structure.

On the structural integrity of the spinel block in the β"-alumina structure

Analysis of 40 compounds with the β′′-alumina structure type has shown that the thickness of the conduction layers for cationic electrical conduction can be accurately estimated on the basis of the unit-cell dimensions.

Site occupancy and lattice parameters in sigma-phase Co–Cr alloys

The neutron diffraction technique was used to determine site occupancies and the unit-cell parameters in sigma-phase Co–Cr alloys. The latter show a linear dependence on temperature, T, with a change of the slope at T ≃ 100 K.

Structures and phase transitions in a new ferroelectric – pyridinium chlorochromate – studied by X-ray diffraction, DSC and dielectric methods

The crystal structures of four phases of a new ferroelectric – pyridinium chlorochromate – are determined by single-crystal X-ray diffraction. Structural, calorimetric and dielectric studies allow for the description and classification of the three phases transitions.

Rationalizing the molecular origins of Ru- and Fe-based dyes for dye-sensitized solar cells

Structure–property relationships are established in a series of Ru- and Fe-based metal-organic dyes that rationalize their optoelectronic performance in dye-sensitized solar cells.

Detailed example of the identification and crystallographic analysis of a pseudo-merohedrally twinned crystal

A detailed description of the crystal structure solution and refinement of a pseudo-merohedrally twinned crystal of an organometallic complex is presented as a guide to the handling of similar non-routine challenging crystal structures. The interpretation of the signs of twinning and the logic behind the selection of the correct space group are explained. In this case the crystal twinning was complicated by pseudo-symmetry of the ionic species and positional disorder of several atoms.

Two novel Zn-MOFs: structures and characterization

Two Zn metal organic frameworks (Zn-MOFs) have been synthesized with a controlled pH environment in the hydrothermal synthesis. Two novel coordination modes between Zn metal and carboxylate were observed in the structures presented. These two compounds show photoluminescence and thermal stability above 673 K.

Structure of the inclusion complex of β-cyclodextrin with lipoic acid from laboratory powder diffraction data

The crystal structure of the inclusion complex of β-cyclodextrin with lipoic acid was determined from laboratory powder diffraction data.

Ab-initio crystal structure analysis and refinement approaches of oligo p-benzamides based on electron diffraction data

The crystal structure of the oligo p-benzamide containing four benzamide units (OPBA4) was solved ab initio from electron diffraction data. The structure solution and refinement strategy was validated on the known structure of OPBA3 and then applied to OPBA4.

Geometry and conformation of cyclo­propane derivatives having σ-acceptor and σ-donor substituents: a theoretical and crystal structure database study

Bond-length asymmetry in cyclopropane rings carrying σ-acceptor or σ-donor substituents has been studied using density-functional theory calculations and analysis of crystal structures in the Cambridge Structural Database. Both methods are in excellent agreement and show that σ-accepting halogen substituents induce positive asymmetry, but that this effect is reversed for σ-donors such as SiH₃ or Si(CH₃)₃.

Structural systematics and conformational analyses of a 3 × 3 isomer grid of fluoro-N-(pyridyl)benz­amides: physicochemical correlations, polymorphism and isomorphous relationships

A 3 × 3 isomer grid of fluoro-N-(pyridyl)benzamides including two polymorphs has been examined to correlate structural relationships between the solid state and ab initio geometry optimizations. Melting point data demonstrate the importance of the substituent position rather than the nature of the substituent.

Form, function and functionality of two dimeric toluene-2,4-diiso­cyanate polymorphs

The crystal structures of two polymorphs of dimeric toluene-2,4-diisocyanate have been solved from high-resolution laboratory X-ray powder diffraction data. A study of their intermolecular energies highlighted the differences in physical properties observed between the two forms.

Symmetry analysis of the structural and magnetic phase transitions in 122 iron arsenides

The magnetic space-group symmetry of the low-temperature antiferromagnetic structure of the 122 iron arsenide (XFe₂As₂) has been identified, and group theory used to analyse the transition(s) between this phase and the room-temperature paramagnetic structure.

Sagrario Martínez-Carrera (1925–2011)

Obituary for Sagrario Martínez-Carrera