On the origin of crystallinity: a lower bound for the regularity radius of Delone sets

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

Blind lattice-parameter determination of cubic and tetragonal phases with high accuracy using a single EBSD pattern

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.

Simulating the diffraction line profile from nanocrystalline powders using a spherical harmonics expansion

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.

Atomic scale analyses of -module defects in an NiZr alloy

This article describes the observation and determination of -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).

A tenfold twin of the CrB structure type

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 -module, and the chiral twin structure being parameterized by a spiral generating formula.

An accurate theory of X-ray coplanar multiple SRMS diffractometry

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.

Intensity distribution profile of double Bragg scattering in the small-angle region from highly oriented pyrolytic graphite

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.

Computer simulations of X-ray spherical wave dynamical diffraction in one and two crystals in the Laue case

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.

Crystal symmetry aspects of materials with magnetic spin reorientation

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

Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector. Corrigendum

A correction is made to the article by van Genderen et al. [Acta Cryst. (2016), A72, 236–242].

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Aperiodic Crystals. From Modulated Phases to Quasicrystals: Structure and Properties