issue contents

ISSN: 2052-5206

August 2009 issue

Highlighted illustration

Cover illustration: Though cyclohexanol is a simple compound it has a rich phase diversity at low temperature. It forms a disordered glassy phase on cooling, but this can be transformed into ordered phases (II), (III) and the metastable (III'), which all have different hydrogen-bonding motifs.  The series of transitions is attributable to the conformational flexibility of the hydroxyl group [Ibberson et  al. (2008). Acta Cryst. B64, 573-582].

research papers

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ABX3 perovskites with both tilting of BX6 octahedra and layered ordering of A cations are examined on the basis of group–subgroup relations. A systematic method for distinguishing the space groups by electron diffraction is proposed.

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The incommensurately modulated structure of the β-Pb2BiVO6 polymorph has been solved using a combination of X-ray single-crystal diffraction, powder diffraction and transmission electron microscopy observations. Phase transitions between the different polymorphs have been characterized both by high-temperature X-ray diffraction and by ionic conductivity measurements.

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Two methods by Voronoi–Dirichlet polyhedra (Voronoi–Dirichlet partition) or tiles (tiling) based on partitioning space are compared to investigate cavities and channels in crystal structures. Both advantages and restrictions of the methods are discussed with respect to fast-ion conductors and zeolites.

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High-resolution synchrotron X-ray powder diffraction and 29Si MAS NMR spectroscopy have been used to determine and refine the crystal structures of synthetic analogues of the mineral leucite.

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The crystal structures of RbBe2BO3F2 and CsBe2BO3F2, previously determined in the space group C2, were redetermined in the space group R32. The structure of the novel compound TlBe2BO3F2 was also determined in R32 and structural trends within this fluoroberyllium borate family are discussed.

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A previously unknown aristotype phase of ferroelectric YMnO3, with a melting point of ∼ 1600 K, is predicted on the basis of the coordinate analysis of its known phases and of those in multiferroic BaTiO3.

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The basic cationic structure of three different members of a new family of anionic conductors, Bi2(n + 2)MonO6(n + 1) (n = 4, 5 and 6), was elucidated mainly by means of high-resolution electron microscopy images based on the previously known structure of the n = 3 phase, Bi10Mo3O24. The models proposed have been successfully tested by HRTEM (high-resolution transmission electron microscopy) image simulation, and electron and powder X-ray diffraction simulations.

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Hydrogen bonds and π–π interactions between nitrile triple bonds in a pair of isostructural cobalt(II) and nickel(II) complexes of the type [M(H2O)3(SO4)(4-CNpy)2], M = Ni, Co, lead to a novel inverse bilayer structure.

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The spin-crossover properties of monoclinic and orthorhombic polymorphs of a cationic iron(III) complex are compared. The packing within the ionic layers in the two polymorphs is very similar, but the layer stacking differs.

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The structures of β- and δ-strontium diformate, and α- and β-strontium fumarate all show a diamond-like strontium arrangement as in strontium acetylene dicarboxylate.

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Experimental electron-density results of eight tripeptides of the type L-Ala-X-L-Ala (AXA) and the corrresponding theoretical results of 20 AXA tripeptides (X varied over all 20 genetically encoded amino acids) were analyzed to provide a quantitative measure for transferability of bond-topological and atomic properties.

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The new compound N-(3-nitrobenzoyl)-N′,N′′-bis(tert-butyl)phosphoric triamide has been synthesized and characterized. Structural properties were analyzed using single-crystal X-ray diffraction, vibrational spectra and theoretical calculations.

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A low-temperature structural phase transition is observed for form (II) of benzocaine (BZC). The new structure [form (III)] is twinned corresponding to a 21 screw rotation parallel to the direction of displacements for hydrogen-bonded ribbons of molecules. No similar phase transition is observed for form (I).

addenda and errata

Acta Cryst. (2009). B65, 516
doi: 10.1107/S0108768109020916

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