The Zintl–Klemm concept applied to cations in oxides. I. The structures of ternary aluminates

The structures of 94 ternary aluminates are reinterpreted on the basis of the Zintl–Klemm concept and Pearson's generalized octet rule. In aluminates of highly electropositive metals such as alkali, alkaline-earth and rare-earth metals, the Al atoms form three-dimensional skeleta which can be interpreted as if the Al atoms would behave as Zintl polyanions, adopting the structure of either main-group elements or Zintl polyanions showing the same connectivity.

The commensurate composite σ-structure of β-tantalum

The single-crystal investigation of the β-Ta self-hosting structure at 293 and 120 K shows that this σ-structure is a two-component [the host (H) and the guest (G)] composite with the same (or a multiple) lattice constants, but different space groups. The phase transition revealed in the thermal process 293 → 120 → 293 K is reversible for H and irreversible for G.

Sodium carbonate revisited

A single-crystal X-ray structure analysis is presented for the incommensurate room-temperature phase γ and for the commensurate phase δ at 110 K of anhydrous sodium carbonate. A previous study of phase δ included only first-order satellites; this study included higher-order satellites. Both phases are compared within the unified superspace group approach.

Cation movement and phase transitions in KTP isostructures; X-ray study of sodium-doped KTP at 10.5 K

An accurate structure model of sodium-doped KTiOPO₄ at 10.5 K has been determined by single-crystal X-ray diffraction. The rigid crystal lattice of TiO₆ octahedra and PO₄ tetrahedra has not been influenced by the temperature change, from room temperature to 10.5 K, and no phase transformation has been detected. However, both potassium cations have moved 0.033 (2) Å along the polar direction.

Structure-forming components in crystals of ternary and quaternary 3d-metal complex fluorides

Rules to predict the crystal structures of complex fluorides M1_nM2_mM3F₆ were formulated using the uniformity criterion for ionic sublattices. The essential role of cationic sublattices and the relationship between the composition of an ionic compound, and the size and charge of ions were analysed under normal conditions, with thermal and high-pressure polymorphic transitions.

Structure of lithium benzilate hemihydrate solved by simulated annealing and difference Fourier synthesis from powder data

The structure of lithium benzilate hemihydrate has been determined from synchrotron powder diffraction data using a simulated-annealing global-minimization algorithm and the long-established difference Fourier maps.

Diffuse scattering and short-range order in uranium iodine phthalocyanine [U_1−xPc₂]I_2−y and the X-ray structure analysis of crystals with diffuse superstructure reflections

The short-range order of both uranium ions and iodine chains [I]_n in two crystals of uranium iodine phthalocyanine has been analysed by RMC simulation of X-ray diffuse scattering. We have shown that arbitrarily regarding diffuse reflections as Bragg reflections in the refinement may produce ambiguous and incorrect results.

Redetermination of the crystal structure of α-copper phthalocyanine grown on KCl

Unlike the α-modifications of platinum phthalocyanine and metal-free phthalocyanine, the α-modification of copper phthalocyanine grown on KCl does not have a herringbone-type molecular arrangement. A classification of the polymorphs of planar phthalocyanines is proposed.

Mechanism of the first-order phase transition of an acylurea derivative: observation of intermediate stages of transformation with a detailed temperature-resolved single-crystal diffraction method

The mechanism of the first-order solid-to-solid phase transition of 1-ethyl-3-(4-methylpentanoyl)urea crystal was clarified by analysing the structure of intermediate stages of the transformation with a detailed temperature-resolved single-crystal diffraction method.

Structural changes of hexa­methylene­tetramine and undecanedioic acid co-crystal (HMT-C11) as a function of the temperature

The structure of the 1:1 adduct of hexamethylenetetramine and undecanedioic acid is investigated. The disorder observed in the O atoms of the carboxylic group is analyzed as a function of the temperature.

Experimental charge density in the transition metal complex Mn₂(CO)₁₀: a comparative study. Erratum

An erratum to the paper by Farrugia et al. (2003). Acta Cryst. B59, 234–247.