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Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206

June 2007 issue

Highlighted illustration

Cover illustration: The cover illustration represents the high- and incommensurately modulated room-temperature phases of Na2CO3 and its reconstructed reciprocal (h2lm) layer [[gamma]-Na2CO3; Dusek et al. (2003). Acta Cryst. B59, 337-352]. Main reflections (open circles) and satellites aligned along parallel lines are indicated. A comparison of the two structures represented by slices parallel to the vertical axis c illustrates their relationship [Arakcheeva & Chapuis (2005). Acta Cryst. B61, 601-607]. [beta]-Na2CO3 at 746 K (C2/m; pseudohexagonal) is shown on the left. All C and Na atoms closer than 3.12 Å are linked. The corresponding non-periodic slice of [gamma]-Na2CO3 indicates how the modulation creates additional close contacts (Ivan Orlov's design is kindly acknowledged).

feature articles


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A generalization of the Zintl–Klemm concept (ZKC) explains the complex structures of alloys as well as the cation arrays of oxides. This generalization helps to establish a univocal link between chemical composition (in terms of Klemm's pseudoatoms) and the structures observed experimentally.

research papers


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Ge2Bi2Te5 in the GeTe–Bi2Te3 pseudobinary system has two single-crystalline phases: a metastable phase with an NaCl-type structure and a stable phase with a nine-layer trigonal structure. These two crystalline phases in Ge2Bi2Te5 have atomic configurations identical to those found in the two corresponding phases of Ge2Sb2Te5.

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A novel systematic classification and a convenient algebraic description of borates were proposed on the basis of the topological structure and polymerization of FBBs (fundamental building blocks) in the borate crystallographic frame. The current work gives an impetus to elucidate topological features in borate chemistry and provides some useful statistical information to design and search for novel borate structures.

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We present the formulae for the calculation of polyhedral volume ratios VA/VB for perovskite-type structures ABX3 in terms of atomic coordinates. The analysis of crystallographic data for approximately 1300 perovskite structures from the Inorganic Crystal Structure Database resulted in the estimated values of ratios at which phase transitions occur.

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The superspace crystal symmetry of two new misfit lamellar thermoelectric cobalt oxides is described. Structural models are deduced from generalized metric considerations and from observed crystal symmetries.

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The crystal structure of the ceria–zirconia solid solution CeZrO4 is refined by Rietveld analysis of neutron diffraction data measured in situ over the temperature range 296–1831 K. The cubic-to-tetragonal phase transition between 1542 and 1831 K is accompanied by the displacement of oxygen atoms and elongation of the c axis.

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The space group of the hexagonal perovskite Ba3Ti2MnO9 has been determined using convergent-beam electron diffraction (CBED) and the microstructure investigated using high-resolution electron microscopy (HREM).

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Owing to the absence of crystals suitable for single-crystal X-ray diffraction, the structure of a new mineral, jadarite, with the composition LiNaSiB3O7(OH), has been determined using laboratory powder diffraction data. Its novel architecture consists of lithium, silicon and two of the B atoms forming unbranched vierer single layers of corner-sharing tetrahedra, themselves decorated by triangular borate groups, and connected by distorted NaO6 octahedra. The structure was validated using ab initio modelling because of the extreme difficulty in obtaining neutron diffraction data from such a boron-rich sample.

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The crystal structures of four compounds – 4′-[2-(tosylamino)benzylideneamino]-2,3-benzo-15-crown-5 (HL), ZnL2, CuL2 and LiNCS·HL, two of which (CuL2 and LiNCS·HL) being determined from synchrotron powder diffraction data – were used in DFT calculations to determine a possible reason for the different ionic selectivities of ZnL2 and CuL2 complexes.

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The reinvestigation of tetraaryltins together with the semantic elucidation of morphotropism revealed that isostructural groups of crystals are occasionally linked by non-crystallographic rotations and/or translations.

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The crystal structures of cyclamic acid and sodium cyclamate together with other cyclamates have been determined in the course of a study on artificial sweeteners.

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An accurate and precise crystallographic description for all atom types has been obtained rapidly for a hydrogenous material by the combined analysis of single-crystal X-ray diffraction and powder neutron diffraction data.

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The structure of the 1:1 compound of cis- and trans-2,3-tetralindiol, the existence of which has been known for nearly a century, has finally been determined. The likelihood of compound formation between stereoisomers is discussed.

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The crystal structures of three similar guaninium salts are described and compared. The investigation of the hydrogen-bond network in these guaninium salts reveals the existence of two ketoamine tautomers, the N9H form and an N7H form.

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The crystal structures of tartaric acid complexes of arginine and lysine provide insight into the invariant and variable features of supramolecular association involving amino acids. The structures also contribute to information about the effect of chirality on such an association.

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Cluster analysis using the program dSNAP has been applied to the conformational analysis of enones and enimines using data from the Cambridge Structural Database.

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The structure of the title compound was solved from laboratory powder data in the space group P\bar 1. Refinement was carried out by restrained Rietveld refinement as well as by structure optimization by energy minimization in the solid state at the DFT level of theory.

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The crystal structures of three pairs of isomeric benzylideneanilines and one pair of isomeric phenylhydrazones are described. The pairs are `bridge-flipped' isomers, related by the reversal of the bridge of atoms connecting the major parts of the molecules; all pairs but one are isostructural.

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Single-crystal neutron diffraction studies showed that the short hydrogen bond between the glycinium cation and the oxalate anion in the title compound is asymmetric in nature with no hydrogen disorder.

short communications


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The structure of L-ornithine hydrochloride was investigated by an invariom refinement and a full multipole refinement, and the resulting electron densities on a grid were compared. Cruickshank's diffraction-component precision index and the suitability factor of Stevens and Coppens are discussed with respect to core scattering and improvement in figures-of-merit by aspherical atom refinements.
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