issue contents

ISSN: 2053-2733

March 2018 issue

Highlighted illustration

Cover illustration: The high brightness, small divergence and high coherence of X-ray free-electron-based sources increase the significance of multiple-scattering effects in perfect crystals. The first experimental observation of the spatial displacement due to multiple scattering of an X-ray beam transmitted by a thin perfect crystal is reported [Rodriguez-Fernandez et al. (2018). Acta Cryst. A74, 75-87]. The right-hand images show the X-ray beam intensity in the near field downstream of a thin diamond single crystal oriented in the Bragg condition at 12 keV for the (220) reflection at 3 eV below (top image) and at the exact Bragg condition (bottom image) of diffraction. The left-hand images are the corresponding simulations based on the dynamical diffraction theory.


research papers

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The first experimental observation of transverse spatial echoes generated by forward Bragg diffraction of an X-ray beam propagating through a perfect thin crystal is reported.

scientific comment

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Around 1965 at the Reactor Centre Netherlands at Petten, Loopstra, van Laar and Rietveld developed `profile refinement'. Although Loopstra had the idea, van Laar worked it out mathematically and Rietveld wrote the computer program, the essential contributions of the first two are forgotten when using `Rietveld refinement'.


research papers

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A routine to extract diffuse-scattering intensities caused by two-dimensional crystalline defects from tomographic electron diffraction data and an algorithm for comparison with simulated diffraction data were developed and applied to intergrown zeolite beta A and zeolite beta B.

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A description of the coordination sequence of the vertex graph of a Penrose tiling is obtained.

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Crystallographic least-squares techniques, a fundamental tool for crystal structure refinement, are used for the first time for ab initio crystal structure solution. No help was needed from other phasing techniques, such as the calculation of electron-density maps.

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A joint refinement model of the spin-resolved one-electron reduced density matrix is described and validated. The new model provides very satisfactory results.

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All homogeneous sphere packings were derived that refer to the trivariant monoclinic lattice complexes with mirror symmetry.

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