issue contents

ISSN: 2053-2733

November 2018 issue

Highlighted illustration

Cover illustration: Ming Han et al. [Acta Cryst. (2018), A74, 616-713] show that a single electron backscatter diffraction (EBSD) pattern can be used for reliable crystallographic characterization of bulk crystalline materials in scanning electron microscopy. The cover image shows an EBSD pattern for tetragonal ZrSiO4. Its Bravais lattice can be accurately reconstructed using only the diffraction geometry extracted from the pattern; no knowledge of the chemical composition or use of a database is required.


research papers

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A new lower bound is proved for the regularity radius of a Delone set in dimensions d greater than or equal to 3.


research papers

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A reliable method which can accurately derive the Bravais-lattice type and lattice parameters of unknown phases from a single EBSD pattern without a priori knowledge is proposed. By solving the geometric relationships in an EBSD pattern based on a huge overdetermined system of equations, error accumulation can be avoided, with the relative errors confined to ∼1% for lattice parameters, <0.4% for axial ratios and ∼0.1° for crystal orientation.

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A spherical harmonics expansion is proposed to model the diffraction line profile from nanocrystalline powders. The procedure is computationally efficient and applicable to any crystallite shape and size.

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This article describes the observation and determination of {\bb Z}-module defects (twins, translation faults and module dislocations) in NiZr by high-resolution electron microscopy (HREM), and scanning transmission electron microscopy bright-field (STEM-BF) and high-angle annular dark-field (STEM-HAADF).

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The structure of the tenfold twins formed by CrB-type NiZr is explained by an idealization of the NiZr crystal structure, involving atoms occupying the nodes of a pentagonal {\bb Z}-module, and the chiral twin structure being parameterized by a spiral generating formula.

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An accurate theory of X-ray coplanar multiple diffraction in an experimental setup that consists of a synchrotron radiation (SR) source, double-crystal monochromator (M) and slit (S), in brief the theory of coplanar multiple SRMS diffractometry, is reported. It is shown that such a setup allows one to measure the rocking curves close to the case of the monochromatic incident plane wave with high-order reflections by monochromator crystals.

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The intensity profile of double Bragg scattering from uniaxial polycrystalline materials, such as highly oriented pyrolytic graphite (HOPG), is calculated theoretically and compared with that observed experimentally. The intensity profile is related to the orientational distribution of crystallites.

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Computer simulations of X-ray spherical wave dynamical diffraction in one and two crystals in the Laue case are reported. A spherical wave is created by an X-ray compound refractive lens. Diffraction focusing phenomena in one crystal and for the reflected beam, as well as in two crystals and for the twice-reflected beam, are simulated and discussed. How these phenomena may be used in an energy spectrometer is investigated.

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The symmetry of materials which undergo a continuous spin reorientation can be only triclinic or monoclinic.

addenda and errata

international union of crystallography

book reviews

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