issue contents

ISSN: 2052-5206

June 2013 issue

Highlighted illustration

Cover illustration: Reduction of volumes of the voids in the crystal structures of DL-alanine and L-alanine on application of 6 GPa of pressure. Yellow voids are shown within the ball-and-stick structure models. The molecules as well as the topologies and symmetries of their packings are preserved over the whole pressure range of 0-6 GPa. See Fig. 4 in Tumanov & Boldyreva [(2012), Acta Cryst. B68, 412-423].

research papers

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The real crystal structure of the (NbSe4)10/3I charge density wave (CDW) compound is studied by simulation of the X-ray diffuse scattering. The average structure of the low-temperature twinned phase is determined and the phase transition is attributed to the formation of a CDW.

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A new compound, hP386-Al57.4Cu3.6Ta39.0, is described in detail by multiple approaches and compared with related structures.

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Differences and quotients can be defined using Friedel pairs of reflections and applied in refinement to enable absolute structure to be determined precisely even for light atom crystal structures.

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New phosphoric triamide structures having different segments [C(=O)NH]P(=O)[N]2, [O]2P(=O)[N] and [N]2P(=O)OP(=O)[N]2 have been analyzed using Hirshfeld surfaces and two-dimensional fingerprint plots, providing a detailed description of salient features in the crystal structures.

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The first example of a single-crystal diffraction study of a high-pressure phase transition in a crystalline amino acid salt hydrate is reported. The transition is accompanied by pronounced discontinuities in the cell parameters and volume versus pressure, although no radical changes in the molecular packing are induced.

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Analysis of 824 crystal structures containing the ethynyl group C—C C—H shows that it acts as a hydrogen-bond donor or acceptor in 87% of those structures, and makes key contributions to crystal packing.

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Absolute structure of 2-methylpiperazine by Flack, Parsons' Q and Hooft methods.

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The molecular geometries and conformations of N-phenyl-4-oxo-4H-2-chromone carboxamides appear to be dependent on the possibility of establishing intramolecular hydrogen bonds.

addenda and errata

Acta Cryst. (2013). B69, 310
doi: 10.1107/S2052519213009068
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