issue contents

ISSN: 2053-2733

July 2003 issue

Highlighted illustration

Cover illustration: Polyhedral representation of voids in the sodium-free sublattice of the crystal structure of NaAlSiO4 zeolite. See Blatov & Shevchenko [Acta Cryst. (2003). A59, 34-44].

research papers

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Methods to determine the axial ratios of primitive and body-centred tetragonal lattices admitting multiplicities Σ lower than a chosen upper limit are developed and applied to produce lists giving all cases with Σ ≤ 5 and the corresponding twin mirror planes.

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The power ratio distribution, the integrated power ratio and the secondary-extinction factor for cylindrical crystals with three kinds of mosaic distributions are calculated and are analyzed to reveal their relationship with the diffraction geometry.

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A `six-beam X-ray section topograph' experiment was performed whose images are in excellent agreement with the images computer-simulated using a theory based on the Takagi–Taupin dynamical theory.

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All homogeneous sphere packings have been derived that refer to the invariant and univariant lattice complexes of the hexagonal crystal family. Numerous examples of corresponding crystal structures are given.

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Two phasing protocols are compared for Xe-apocrustacyanin A1 as a test case. The L1-absorption edge optimized Xe f′′ signal using 2.0 Å wavelength yielded high-quality electron-density maps even with modest redundancy (7) from a single data set.

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Symmetry in reference-beam diffraction experiments leads to a fourfold measurement redundancy of any triplet-phase δ in a complete 360° rotation, with two of the four cases corresponding to measurements of the coupling Friedel's mate that may give rise to enhanced three-beam interference effects.

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Accurate charge deformation maps in rutile are obtained by using accurate low-order X-ray structure factors measured by quantitative convergent-beam electron difraction.

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Methods of determining the combinatorial symmetry of a net and of determining whether two nets are combinatorially isomorphic are described.

short communications

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The symmetry point-group statistics for all combinatorially non-isomorphic simple 14- (339722) and 15-hedra (2406841 in total) are contributed in the paper for the first time.

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A scattering-angle-dependent formula has been developed and used to estimate the anomalous signals in single-wavelength anomalous diffraction (SAD) experiments.

international union of crystallography

book reviews

Acta Cryst. (2003). A59, 434
doi: 10.1107/S0108767303001697

Acta Cryst. (2003). A59, 436
doi: 10.1107/S0108767303010870
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