issue contents

ISSN: 2052-5206

October 2011 issue

Highlighted illustration

Cover illustration: The cover picture highlights an artefact in the electrostatic potential of the macrolide antibiotic roxithromycin as derived via multipole refinement of X-ray diffraction data.  Ignoring the hydrogen disorder (left) in the oxime chain leads to a falsely positive electrostatic potential there as a result of the multipole model's being flexible enough to fit the averaged electron density.  If the invariom formalism, which uses theoretical electron density, is applied to the disordered region (right) the artefact disappears.  A procedure for obtaining reliable electron density distributions in the presence of disorder has been proposed [Holstein et al. (2010). Acta Cryst. B66, 568-577].

research papers

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Crystallization of a sputtered Sb8Te3 film was investigated by powder X-ray diffraction.

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Rietveld refinement of different structural models using neutron diffraction data for a series of powders of lead zirconate titanate, PbZr1 − xTixO3, is described.

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Calcium bis(hydrogen methylphosphonate), Ca(CH3PO3H)2, and lithium hydrogen methylphosphonate, Li(CH3PO3H), have been studied by means of an analysis of the experimentally determined charge density accompanied by DFT calculations. Hyperpolarization and polarization effects have been assessed.

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Powder diffraction patterns of Tl2(SC6H4S) and Tl2(SeC6H4Se) appear to lead to structures with one formula unit in the irreducible cell, but these have impossibly close H—H contacts. Only on very close inspection were additional weak reflections found that arise from orientational ordering of the phenylene bridges between the Tl—S or Tl—Se layers.

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α-Agostic interactions are revealed in one of a series of pentamethylcyclopentadienyltantalum imido complexes. Reactions of these complexes with pentafluorophenol afford chemical products that are influenced by electronic and steric effects, as shown by structural analysis.

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The electron density features of substituted hydropyrimidine derivatives were characterized using the QTAIMC descriptors derived from the X-ray experimental electron density and DFT calculations. The application of these descriptors as transferable quantities suitable for prediction of the chemical properties of the molecular systems is discussed.

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The crystal structures of the dichlorobenzaldehyde isomers are analyzed in terms of the geometry and energies of their intermolecular interactions.
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