issue contents

ISSN: 2053-2733

November 1997 issue

Highlighted illustration

Cover illustration: A structural model of the decagonal Al-Pd-Mn quasicrystal, which consists of clusters represented by decagons and ten pentagons surrounding each decagon. This is obtained from a periodic structure in five-dimensional space by taking a three-dimensional section. Courtesy of A. Yamamoto.

research papers

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X-ray elastic scattering factors for ground-state neutral atoms (H through Xe) have been calculated from the relativistic multiconfiguration Dirac–Fock wavefunctions. The results have been fitted to six-Gaussian analytical expressions for the sinθ/λ ranges of 0–2, 2–4 and 4–6Å−1. The atomic energies and second moments are also presented.

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All the components of gyration tensor and birefringence of L-aspartic acid have been successfully measured as a function of the temperature. It is of special interest that the chirality index of aspartic acid was found to be almost the same as that of glutamic acid.

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Points of best fit between pairs of lattices are found using higher-dimensional lattices. It constitutes a generalization of the coincidence lattice.

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Dynamical diffraction in an epilayer crystal, as thin as 100Å, is shown to modify significantly the field pattern of grazing-angle X-ray standing waves produced by the substrate. The technique is applied to the determination of the registration and the ordering of a Ca0.39Sr0.61F2 epilayer on GaAs (111).

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Phases obtained by direct methods are improved by using information on the heavy-atom structure and a suitable solvent-flattening technique.

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The probabilistic estimate of quartet invariants is obtained when prior information on well oriented molecular fragments is available.

short communications

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Two formulae for the number of sublattices of a given index k of an n-dimensional lattice are presented which give the result in a considerably quicker way than any previous method.

Acta Cryst. (1997). A53, 809
doi: 10.1107/S0108767397010325
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A proof is given that the root-mean-square deviation between more than two vector sets after optimal superposition induces a metric.

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A previous theoretical formulation of X-ray moiré fringes for a bicrystal model is explained to clarify the meanings of the formulation.

Acta Cryst. (1997). A53, 813
doi: 10.1107/S0108767397010891

international union of crystallography

book reviews

Acta Cryst. (1997). A53, 855
doi: 10.1107/S0108767397099789

books received

Acta Cryst. (1997). A53, 856
doi: 10.1107/S0108767397099741
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