issue contents

ISSN: 2053-2733

July 2018 issue

Highlighted illustration

Cover illustration: `Recipes' to make materials with emergent properties as complex as magnetoelectricity can be rationally designed by mixing `ingredients' together consisting of the symmetry-breaking degrees of freedom accessible through chemical, compositional and physical control of the perovskite structure [Senn & Bristowe (2018). Acta Cryst. A74, 308-321]. The image shows how the symmetry breaking associated with cation layering and two types of magnetic ordering can combine, driving at their intersection off-centre ferroelectric displacements. Image courtesy of Mr Paul Biddle and Dr Mark Senn, drawn using ISODISTORT [Campbell et al. (2006). J. Appl. Cryst. 39, 607-614] and VESTA [Momma & Izumi (2011). J. Appl. Cryst. 44, 1272-1276].


scientific commentaries

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The new approach to the design of technologically important perovskites described by Senn and Bristowe [Acta Cryst. (2018), A74, 308–321] is discussed.

feature articles

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A systematic overview of the effects of common aberrations in time-of-flight neutron powder diffraction data on real-space pair distribution functions is provided, and methods and best practices to mitigate these effects are discussed.

research papers

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A symmetry-motivated approach for designing perovskites with ferroic and magnetoelectric couplings is proposed. The results highlight which kinds of magnetic orderings and structural distortions need to coexist within the same structure to produce the desired couplings.


research papers

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A numerical method for generating shape functions of non-spherical nanoparticles for use in small-box refinements of pair distribution function data is presented and implemented on several sets of simulated and experimental data. With this approach, physically relevant size parameters for simple and complex nanoparticle shapes can be refined from the data.

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The reticular conditions for the occurrence of plesiotwins and diperiodic twins are systematically analysed.

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Molecular orbitals of an organic compound were successfully obtained by X-ray molecular orbital analysis. The quantum-mechanical and crystallographic framework of the method is described.

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Aperiodic crystals, including ice and opaline silica, are described using a hidden Markov model, deriving expressions for the scattering cross sections. The reversibility of aperiodic crystals is discussed.

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Crystal structure solutions from fibre-textured crystals within thin films are frequently achieved by grazing-incidence X-ray diffraction experiments. In the present work, analytical mathematical expressions are derived for the indexing of experimental diffraction patterns.

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The idea of symmetry order, which describes the rotational symmetry types of tilings in the hull of a given substitution, is introduced. Two substitutions giving rise to six- and sevenfold rotation-invariant tilings are also presented.

short communications

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Spatio-temporal crystallographic point groups with time translations and time inversion are derived and tabulated.


book reviews

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