issue contents

Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206

August 2012 issue

Highlighted illustration

Cover illustration: A high-angle annular darkfield scanning transmission electron microscopy image of the decagonal quasicrystal Al72Co8Ni20 overlaid with a structure model. Clusters of type 1 (occupied center) highlight transition metal sites (white spheres) and clusters of type 2 (empty center) possess both transition metal and mixed aluminum/transition metal (red) sites. Decagonal-shaped clusters are outlined and exhibit two types of overlap as a unifying building feature of aperiodic quasicrystals of decagonal Al-Co-Ni, Al-Co-Cu and Al-Fe-Ni [Deloudi et al. (2011). Acta Cryst. B67, 1-17, based on Abe & Tsai (2004) J. Non-Cryst. Solids, 334, 198-201]. The 2011 Nobel prize in chemistry was awarded to D. Shechtman for his discovery of quasicrystals.

research papers


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The system of flexible composition Bi2(n + 2)MonO6(n + 1) is described within the superspace formalism with two models, depending on the parity of the parameter n.

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Two commensurate members (m = 4, 5) of the 2212 stair-like family of compounds with the composition [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] have been analyzed and refined in the (3 + 1)-dimensional superspace framework. Both compounds are described by a unique model, including displacive modulations. The assumption of the validity of the proposed model for a range of compositions allows a realistic prediction of the structures of other members of the family.

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A detailed analysis of correlations between structural features and cation conductivity is performed for KAlO2 polymorphs in a wide temperature range of 300–1023 K. To explore the migration maps of K+ cations we have used neutron diffraction data and applied for the first time a novel algorithm based on the natural tiling concept and implemented it into the program package TOPOS.

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The structure of ternary oxides and chalcogenides of alkali metals can be better understood by assuming the electron transfer between cations, in an extension of the Zintl–Klemm concept.

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The necessary crystallographic input data are given for electronic-structure calculations of supercells with the (111), (001) or (110) orientations. They are applied to calculations on GaAs/AlAs superlattices of different thicknesses.

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Acetonitrilediaqua-κ1O-nitrato-κ2O-nitratonickel(II) 15-crown-5 acetonitrile solvate was studied by single-crystal X-ray diffraction at intervals of 10 K in the range 90–273 K as the crystal passed, without obvious damage, through three phase transitions. The phase sequence includes an intermediate modulated phase that seems to be a kind of striped hybrid of the phases stable at immediately higher and lower temperatures.

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Bis(benzylamino)silver(I) benzylcarbamate contains silver atoms coordinated to two nitrogen atoms of amino groups from different benzylamine molecules; metal–oxygen interactions are absent in the crystal structure. The title compound exhibits fluorescence properties.

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The crystal structure of L-arabinitol at room temperature was solved from its powder X-ray diffraction pattern. The starting structural model was found by the simulated annealing method. The structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. The H atoms of hydroxyl groups were localized by a minimization of the crystalline energy.

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Structural changes in DL-alanine at pressures up to 8.3 GPa are not related to phase transitions.

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The kinetics of the 9-methylanthracene photodimerization reaction was examined by time-resolved powder diffraction using a CCD detector and parametric Rietveld refinement.

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Cocrystallization attempts with 5-fluorocytosine yielded eight cocrystals and two structures of a single compound. In six cocrystals, the expected heterodimers held together by two or three hydrogen bonds are present. Ab initio energy calculations helped to rationalize the intermolecular hydrogen-bonding patterns observed in the crystal structures.

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Five cocrystals (four with 5-fluorocytosine and one with 6-aminoisocytosine) are presented to study the influence of complementary binding on conformational flexibility and the tautomeric equilibrium.

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A structural study of 42 salt forms of the phenylethylamine tyramine examines cation conformation, cation packing and hydrogen bonding as well as showing that hydrate formation is favoured both by higher total numbers of potential hydrogen-bond acceptors and donors and by lower donor:acceptor ratios.

addenda and errata


Acta Cryst. (2012). B68, 465
doi: 10.1107/S010876811203193X
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