Introduction to the special issue on high-resolution X-ray diffraction and imaging

The latest virtual special issue of Journal of Applied Crystallography features some highlights of the 13th Biennial Conference on High-Resolution X-ray Diffraction and Imaging (XTOP 2016), held in Brno, Czech Republic, in September 2016.

Threefold rotational symmetry in hexagonally shaped core–shell (In,Ga)As/GaAs nanowires revealed by coherent X-ray diffraction imaging

Coherent X-ray diffraction imaging was used to detect a threefold rotational symmetry in hexagonally shaped single semiconductor nanowires. The core–shell–shell structure was resolved by probing symmetric hhh Bragg reflections.

Incorporation of interfacial roughness into recursion matrix formalism of dynamical X-ray diffraction in multilayers and superlattices

Interfacial roughness is considered as a transition layer. A method of calculation of diffraction scans from multilayered structures with interfacial roughness, which is both fast and free of numerical errors, is developed.

X-ray dynamical diffraction in amino acid crystals: a step towards improving structural resolution of biological molecules via physical phase measurements

X-ray phase measurements have been applied to study hydrogen bonds and radiation damage in amino acid crystals.

Reconstruction of the near-field distribution in an X-ray waveguide array

Multi-waveguide interference can be verified experimentally by reconstructing the near-field from the measured far-field diffraction pattern. This enables a direct visualization of the near-field interference pattern and the diversity of fields that can be created by multi-waveguide design, in particular a secondary quasi-focal spot. Numerical propagation using the design parameters is compared with the phase retrieval results.

Interface-sensitive imaging by an image reconstruction aided X-ray reflectivity technique

This article describes interface-sensitive imaging of heterogeneous thin films by an image reconstruction aided X-ray reflectivity technique with an 8 mm-wide parallel beam; the possibility of extracting micro-X-ray reflectivity profiles from the same data collection is discussed.

Structure diagnostics of heterostructures and multi-layered systems by X-ray multiple diffraction

Opportunities of multi-beam X-ray diffraction are demonstrated for determination of lattice strains in heterostructures and multi-layered systems.

X-ray topography of subsurface crystal layers

The practical application of the modified Berg–Barrett topographic method in a skew asymmetric scheme of X-ray diffraction is presented. The method is used for the study of the defect structure of CdTe crystals and Cd_1−xHg_xTe/CdTe epitaxial layers after the influence of different external factors (ion implantation and etching).

An in situ USAXS–SAXS–WAXS study of precipitate size distribution evolution in a model Ni-based alloy

Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS–SAXS–WAXS) provides in situ evaluation of the precipitate size distribution (PSD) and phase structure temporal evolution during heat treatment. A method for extraction of an arbitrary PSD in the presence of interparticle interactions is described and illustrated for study of PSD evolution.

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

The lognormal particle size distributions of supported nanoparticles were obtained from their pair distribution function and the results were validated with scanning transmission electron microscopy.

Simultaneous determination of high-temperature crystal structure and texture of synthetic porous cordierite

For the first time, high-temperature evolution of the crystal texture in porous synthetic cordierite was observed by neutron diffraction. The data quality allowed determination of the lattice structure evolution, which turns out to be more significant than the crystal texture change as a function of temperature.

Growth of a bulk-size single crystal of sulphamic acid by an in-house developed seed rotation solution growth technique and its characterization

A good quality bulk-size sulphamic acid single crystal was grown by adopting a newly designed seed rotation technique. The crystalline perfection of the grown crystal was assessed using high-resolution X-ray diffraction and it was found to produce a single-peak rocking curve with an FWHM of 8.0′′. The optical, thermal and shock damage threshold behaviours of the crystal have been measured to assess its optimization for device fabrication.

Investigations into the phase composition of zirconia-based sinters with an axial texture

This paper describes the multiaxial texture of zirconia sinters used as metering nozzles and describes the correct method of phase composition determination using X-ray diffraction. Owing to phase composition changes during sample preparation, testing should be carried out on solid samples and the results corrected.

Bayesian approach to powder phase identification

A Bayesian approach to formulation of a search–match strategy for powder phase identification is proposed. Even for a simple exponential model of prior probabilities the approach provides good agreement with known results for several testing examples.

Appearance of efficient luminescence energy transfer in doped orthovanadate nanocrystals

Efficient luminescence energy transfer in doped orthovanadate nanocrystals is reported.

The origin of striation in the metastable β phase of titanium alloys observed by transmission electron microscopy

In the present work, the striations and diffraction characteristics of the β phase of Ti-5553 alloy are thoroughly investigated.

Robust X-ray angular correlations for the study of meso-structures

The theoretical limitations and experimental challenges of X-ray angular correlation analysis methods are investigated. Using a combination of simulated data and measurements on challenging meso-cluster samples, prepared using lithography and self-assembly, the primary experimental challenges are explored. Background scattering, data masking and inter-object interference are identified as primary challenges. Strategies to overcome correlation artifacts are presented.

Qu­antitative phase analysis using observed integrated intensities and chemical composition data of individual crystalline phases: qu­antification of materials with indefinite chemical compositions

A quantitative phase analysis technique, which can derive weight fractions of individual crystalline phases from their observed integrated intensities and chemical composition data, has been applied to the quantification of materials whose chemical compositions are unknown or indefinite because of substitutional replacements, nonstoichiometric composition etc.

Epitaxial Ni nanoparticles on CaF₂(001), (110) and (111) surfaces studied by three-dimensional RHEED, GIXD and GISAXS reciprocal-space mapping techniques

An advanced three-dimensional reciprocal-space mapping by reflection high-energy electron diffraction (RHEED), grazing-incidence X-ray diffraction (GIXD) and grazing-incidence small-angle X-ray scattering (GISAXS)has been applied to study arrays of magnetically ordered Ni islands grown epitaxially on the surface of differently oriented CaF₂/Si layers.

Calculation of two-dimensional scattering patterns for oriented systems

A versatile procedure to calculate two-dimensional scattering patterns from oriented systems is presented.

Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings

This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation.

Crystallographic texture of straight-rolled α-uranium foils via neutron and X-ray diffraction

The bulk and surface textures of recrystallized straight-rolled α-uranium foils are established by both neutron and X-ray diffraction and discussed relative to the existing literature on α-uranium processing textures.

Instrumental resolution as a function of scattering angle and wavelength as exemplified for the POWGEN instrument

A fundamental description of the instrument resolution file is elaborated for the angular- and wavelength-dispersive cases of Rietveld refinement, exemplified for the POWGEN instrument. It is shown how to refine the necessary profile function parameters from a dataset measured on a diamond reference sample. The analysis is performed in a two-dimensional refinement space based on the convenient variables d and d_⊥.

Intercalated water in multi-layered graphene oxide paper: an X-ray scattering study

An X-ray scattering study of intercalated water in multi-layered graphene oxide paper during hydration and thermal dehydration processes is presented. The evolution of X-ray scattering features depending on the presence and the type of intercalated water is discussed with the help of a simple structural model.

Serial electron crystallography: merging diffraction data through rank aggregation

Rank aggregation is used as an alternative approach for merging serial electron crystallography data. The described algorithm avoids the problem of scaling entirely and is insensitive to errors in the reflection intensities.

Use of Wyckoff position splittings in the supercell model of crystals with point defects

The article considers supercell symmetry and Wyckoff position splittings for the description of defective crystals.

Single-shot full strain tensor determination with microbeam X-ray Laue diffraction and a two-dimensional energy-dispersive detector

By simultaneously measuring changes in energy and reflection angle of Laue spots with respect to a reference position, it is possible to measure all lattice parameters of a unit cell and calculate the full strain/stress tensors in a single-shot experiment with high spatial resolution.

Direct protein crystallization on ultrathin membranes for diffraction measurements at X-ray free-electron lasers

In situ protein crystallization on highly X-ray transparent nanomembranes is described and an application is outlined for the collection of diffraction data at X-ray free-electron lasers.

Scattering from surface fractals in terms of composing mass fractals

The scattering properties of surface fractals are studied by means of their decomposition into a sum of mass fractals.

Simple and efficient system for photoconverting light-sensitive proteins in serial crystallography experiments

The design and application of an enclosed micro-device for generating laser-induced semi-stationary states in light-sensitive microcrystals are described. The setup is suitable for time-resolved serial crystallography at synchrotrons and X-ray free-electron lasers.

Direct measurement of local constitutive relations, at the micrometre scale, in bulk metallic alloys

The local mechanical behavior of a bulk stainless steel crystal is measured directly, at the micrometre scale, by combining total strain measurements with elastic strain measurements.

CrystalWalk: crystal structures, step by step

CrystalWalk is a crystal editor and visualization software designed for teaching materials science and engineering. Based on WebGL/HTML5, it provides an accessible and interactive platform to students, teachers and researchers.

SLADS: a parallel code for direct simulations of scattering of large anisotropic dense nanoparticle systems

SLADS is a parallel code for direct simulations of single-shot X-ray scattering of large anisotropic dense nanoparticle systems of arbitrary species and atomic configurations. Particles can be of arbitrary shapes and dispersities, and interactions between particles are considered.

Processing two-dimensional X-ray diffraction and small-angle scattering data in DAWN 2

The Powder Calibration and Processing packages implemented in DAWN 2 provide an automated diffraction-geometry calibration and data processing environment for two-dimensional diffraction experiments. The customizable processing chains permit the execution of data processing steps to convert raw two-dimensional data into meaningful data and diffractograms. The provenance of the processed data is maintained, which guarantees reproducibility and transparency of the data treatment.

DxTools: processing large data files recorded with the Bruker D8 diffractometer

A simple, free and open-source program is presented that allows processing of large diffraction data files recorded with the Bruker D8 diffractometer. It can be downloaded from https://aboulle.github.io/DxTools/.

A microcontroller for in situ single-crystal diffraction measurements with a PILATUS-2M detector under an alternating electric field

A new data acquisition system is proposed for in situ single-crystal diffraction with a pixel area detector under an alternating electric field.

The ash heap of crystallography: restoring forgotten basic knowledge. Corrigendum

One imprecise and one incomplete statement in the article by Nespolo [J. Appl. Cryst. (2015), 48, 1290–1298] are corrected.

Optically Induced Nanostructures. Biomedical and Technical Applications