issue contents

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767

December 2016 issue

Highlighted illustration

Cover illustration: Cover images courtesy of (clockwise from top left) Stiers et al. [J. Appl. Cryst. (2016), 49, 2235-2243], Venkatakrishnan et al. [J. Appl. Cryst. (2016), 49, 1876-1884], Glazer [J. Appl. Cryst. (2016), 49, 2276-2278] and Yadav et al. [J. Appl. Cryst. (2016), 49, 2053-2062].

editorial


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This open-access collection of 11 selected articles covers a small but quite diverse and interesting part of the much wider range of scientific topics presented at the 16th International Conference on Small-Angle Scattering (SAS2015) in Berlin. The topics contained here describe the particular directions in which small-angle scattering is developing at the current moment and which will become increasingly important in the future. The virtual special issue is available at http://journals.iucr.org/special_issues/2016/sas2015/.

research papers


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The CCP-SAS project is currently developing software for the atomistic and coarse-grained molecular modelling of X-ray and neutron small-angle scattering data. Its computational framework is described, alongside applications in biology and soft matter.

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This paper presents an accurate numerical algorithm for simulating grazing-incidence small-angle X-ray scattering patterns of nanostructures using the multi-slice distorted-wave Born approximation. The method overcomes the typical challenge of requiring the users to manually specify a way to approximate their samples by utilizing properties of Fourier transforms to automate the computation.

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A high-flux Ge(111) X-ray beam compressing channel-cut monochromator with high compression ratio based on a strongly asymmetric diffraction was designed and successfully realized by a pilot application of the single-point diamond technology. Comparative testing demonstrates the potential of the new design and related technology, with direct implications for high-throughput X-ray laboratory setups, in particular those with microfocus X-ray sources.

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The (001) and (010) surfaces of hydroxylapatite are key to understanding and modulating the mineral–organic interactions in bone tissues. The present work provides the structural and electrostatic properties of both stoichiometric and carbonated hydroxylapatite surfaces obtained with an ab initio quantum mechanics approach.

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The strain profile in a YZrO3 thermal barrier coating has been measured and shows possible mechanisms of in-service failure. The method relies on deconvoluting diffraction patterns at different depths for the reflection geometry used. The nondestructive test could be applied to whole fabricated components

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The application of a robust generalized linear model framework for the modelling of reflection backgrounds in X-ray diffraction images is described.

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This article reports on the critical structural factors dictating the selection of optimum crystallographic orientation relationship in a structurally complicated system such as the rutile–garnet system.

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A basic free database with more than 400 magnetic structures has been developed. Its section on incommensurate structures, described under the framework of superspace symmetry, is presented.

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The article explores the stress that develops during the growth of Ge quantum dots in a silica matrix, and how it affects the material properties.

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Dense stacking faults in a supersaturated nitrided layer produced on austenitic stainless steel were systematically investigated by transmission electron microscopy, and then a novel microstructure model of clustered stacking faults embedded in a face-centred cubic structure was built.

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An operando setup that enables deep insights into the working mechanisms of electrode materials under working conditions using quasi-simultaneous X-ray diffraction, XANES and EXAFS analysis is described.

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A full description of the lattice dynamics and elasticity of SrCO3 is reported, based on a combination of first principles calculations and experimental measurements.

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A stress measurement technique based on diffraction analysis developed for thin metal sheets under large plastic deformation was evaluated. Particularly, the uncertainty of the measurement technique has been quantified by perturbing the elastic diffraction strain and diffraction conditions in a Monte Carlo virtual experiment for an interstitial-free steel.

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A combination of microfluidics with X-ray techniques has been used to perform dynamic structural studies on nanoparticulate formulations.

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This publication describes the combination of size exclusion chromatography with small-angle neutron scattering in situ. The need for this technique and the progress achieved thanks to it are illustrated by relevant examples.

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A new methodology has been developed to determine the fraction of open and closed porosity in rocks, without reaching the zero average contrast condition, using (ultra-)small-angle neutron scattering.

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The novel orientation relationship, crystallographic morphology and defect structure across interfaces of the Mg2Y precipitates in an as-cast Mg–Cu–Mn–Zn–Y damping alloy are reported. These results shed light on the formation of moveable dislocations and their association with the damping properties, which are critical in the microstructure design of damping Mg alloys.


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An X-ray cross-correlation study with emphasis on colloidal crystals is presented and demonstrates how to access higher-order structure beyond pair correlations. In this way symmetries of the crystal can be determined that are inaccessible in conventional crystallography.

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Diiso­propyl­ammonium bromide single crystals with twinned structure were grown by the slow evaporation technique. Their properties have been investigated by Hirshfeld surface, ferroelectric and photoluminescence analysis.

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Three-component fluids can exhibit structured density fluctuations, and their small-angle scattering patterns present similarities to those of classical microemulsions. One general analytical expression with two additive contributions (one for the two immiscible fluids and a smaller one for a structured fluid) allows the whole phase diagram to be mapped in the single-phase domain.

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It is demonstrated that measurement of a surface acoustic wave amplitude can be performed on a laboratory diffractometer with a careful experimental procedure and an accurate data analysis. The importance of the footprint reduction and geometrical correction factors to account for finite experimental resolution is emphasized.

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A haptic interface and related database are used to assess crystallization screening, share results and enable efficient in situ diffraction characterization of the resulting crystals.

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Överlåtaren is a program package to transfer and visualize off-specular data in q space, to improve data treatment and accessibility.

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The magnetically oriented microcrystal suspension method is combined with the shutterless continuous rotation method in an attempt to determine the crystal structures from microcrystalline powder samples.

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A statistical method is discussed, which solves the problem of bias in fitted versus observed diffraction intensities for quasicrystals.

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By using intrusive and scattering techniques, the characteristics of the porous network of a geopolymer and its evolution over time are determined according to the chemical formulation parameters.

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α-Quartz has been re-investigated up to 19 GPa in various pressure media to provide precise equation-of-state parameters for its wide applicability as an internal diffraction standard in high-pressure experiments with diamond-anvil cells.

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SnSe undergoes a phase transition immediately below the maximum thermoelectric performance temperature. The present in situ neutron powder diffraction study establishes correlations between the structural evolution and the thermoelectric properties

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Theoretical pole figures of 12 different twin laws for plagioclase were generated. The plagioclase twin laws in a basalt were investigated by comparing the pole figures obtained from electron backscatter diffraction with the theoretical ones

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Ultra-small-angle X-ray scattering measurements were performed on pure Ni and SiC-doped Ni samples to examine the distribution of SiC nanoparticles.

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This paper reports the characterization of subnanometre Cr/Sc multilayers through the application of several analytical experiments. A combined analysis is shown and verified by Markov chain Monte Carlo sampling.

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A new approach is introduced for the fast comparison of molecular packing and the identification of identical crystal structure motifs, and it is tested on some real examples. The packing similarity is calculated from a simple formula involving the distances between molecular centres and the relative orientations of molecular entities inside a finite molecular cluster.

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A numerical method is presented which allows the calculation of the contrast factors of a broad range of radiation defect types in hexagonal materials. Numerical values of average contrast factor parameters for six dislocation loop types as a function of ellipticity are calculated and tabulated for ten hexagonal materials in order to provide a database for future line profile analysis work.

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The implementation of Bayesian data analysis techniques for refinement of diffraction patterns is presented. The effectiveness of the method is shown through example refinements of a variety of neutron diffraction patterns from real materials.

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A combination of small- and ultra-small-angle X-ray scattering enabled the resolution of important intracellular constituents in Escherichia coli (ribosomes, DNA and proteins). The impact of treatment with three antibiotic agents was monitored.

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A novel iterative combinatorial nanoscale search based on the application of cross-sectional synchrotron X-ray nanodiffraction and cross-sectional nanoindentation is used to refine the relationship between deposition conditions, microstructure and properties of nanostructured TiAlN thin films. Using three iterative steps, a nanolamellar TiAlN thin film with a maximal hardness of ∼36 GPa is developed.

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This paper reports on quasi-fivefold symmetric electron diffraction patterns observed in multiply twinned silicon thin films after epitaxy breakdown; the weight of twinned orientations compared to that of random microcrystalline orientations is determined. The origins of twinning and multiple twinning during epitaxy breakdown are discussed.

teaching and education


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A 2 week module on macromolecular crystallography was introduced into an undergraduate biochemistry class, including the use of remote data collection at a synchrotron X-ray source.

short communications


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A diffraction pattern simulation of cellulose fibrils is presented, using a modification of the Debye formula in cylindrical coordinates. Pair distances are labelled by atom type and quantized using a two-dimensional histogram, which greatly decreases the computation time and maintains a smaller R factor.

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A method is given for choosing the relative counting times for the sample-in-container and empty container parts of a fixed-duration scattering experiment in order to minimize the statistical error on the container-corrected intensity.

computer programs


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A webserver, titled ContaMiner, has been established, which allows fast molecular-replacement-based screening of crystallographic data against a database (ContaBase) of currently 62 potential contaminants. ContaMiner enables systematic screening of novel crystals at synchrotron beamlines, and it would be valuable as a routine safety check for `crystallization and preliminary X-ray analysis' publications.

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FAULTS, an accessible program for refining X-ray and neutron diffraction patterns of materials with planar defects, is introduced.

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The program COMPaRS characterizes similarity between two crystallographic maps using a method inspired by visual map comparison.

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Fourier synthesis is demonstrated for teaching purposes using two simple computer programs.

book reviews


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