Introduction to the special issue on Ptychography: software and technical developments

A virtual special issue of Journal of Applied Crystallography brings together 14 articles from developers and practitioners in the field of ptychography, highlighting some developments in software and algorithms, instrumentation, technical requirements, and applications.

Upscaling X-ray nanoimaging to macroscopic specimens

In the era of diffraction-limited storage rings, can X-ray nanoimaging be extended to millimetre- or even centimetre-sized specimens such as whole mouse brains? The authors believe so and provide size-dependent imaging time and resource estimates based on calculated flux requirements and recent method developments in related disciplines.

The anisotropy in the optical constants of quartz crystals for soft X-rays

The refractive index of a y-cut SiO₂ crystal surface is reconstructed from polarization-dependent soft X-ray reflectometry measurements in the energy range from 45 to 620 eV. The reconstructed anisotropy in the optical constants is also confirmed by ab initio Bethe–Salpeter equation calculations of the O K edge.

Bent Laue crystal anatomy: new insights into focusing and energy-dispersion properties

A new theoretical approach has been developed to provide an intuitive view of the focusing and energy-dispersion properties of bent Laue crystals.

Finding the best-fit background function for whole-powder-pattern fitting using LASSO combined with tree search

The linear background function to be used in whole-powder-pattern fitting is derived by applying least absolute shrinkage and selection operator (LASSO) and tree search. It gives excellent fits with a smaller number of adjustable parameters than the currently used polynomials, without introducing undulation into the calculated background curve. Basic algorithms used in statistics and machine learning are demonstrated to be useful in developing an analytical model in X-ray crystallography.

Influence of surface relaxation on the contrast of threading edge dislocations in synchrotron X-ray topographs under the condition of g · b = 0 and g · b × l = 0

Surface relaxation contributes to the formation of residual contrast of threading edge dislocations in X-ray back-reflection topographs under g · b = 0 and g · b × l = 0 conditions.

Generating the atomic pair distribution function without instrument or emission profile contributions

A method for generating the atomic pair distribution function from powder diffraction data that removes instrument and emission profile aberrations has been developed. The method uses a nonlinear least-squares deconvolution technique incorporating penalty functions as implemented in the computer program TOPAS.

Development of spin-contrast-variation neutron powder diffractometry for extracting the structure factor of hydrogen atoms

A spin-contrast-variation neutron powder diffractometry technique is developed, where the coherent scattering length of hydrogen is controlled by proton polarization. This technique extracts the hydrogen structure factor, i.e. the contribution of hydrogen atoms to a crystal's structure factor.

Mitigating background caused by extraneous scattering in small-angle neutron scattering instrument design

Measurements and methods of mitigation for small-angle neutron scattering instrument background caused by extraneous scattering from surfaces are presented.

Evolution of the analytical scattering model of live Escherichia coli

Structural and compositional information about Escherichia coli cells is summarized and translated into an analytical multi-length-scale scattering form factor model of live bacterial suspensions.

Tomographic X-ray scattering based on invariant reconstruction: analysis of the 3D nanostructure of bovine bone

A new tomographic approach using X-ray scattering is presented, allowing the characterization of the 3D nanostructure of hybrid materials.

Line profile analysis of synchrotron X-ray diffraction data of iron powder with bimodal microstructural profile parameters

Synchrotron X-ray diffraction data of Fe powder have a super-Lorentzian peak shape with anisotropic peak broadening. Detailed microstructural (unimodal and bimodal) analyses were carried out using the Rietveld method, modified Williamson–Hall plots and whole powder pattern modelling to investigate these features of the diffraction pattern. The bimodal analysis approach gives improved profile fitting, with the two components of the microstructure having different dislocation densities and a broad lognormal crystalline domain size distribution.

Crystal orientation and detector distance effects on resolving pseudosymmetry by electron backscatter diffraction

The effects of crystal orientation and detector distance on the ability to resolve pseudosymmetry using new intensity-based indexing methods of electron backscatter diffraction are studied. These results quantitatively demonstrate that certain orientations are significantly easier to correctly index and illustrate the clear benefit of shorter detector distances.

Removal of spurious data in Bragg coherent diffraction imaging: an algorithm for automated data preprocessing

An algorithm for automated identification and removal of spurious data from Bragg coherent diffraction imaging data is presented. This algorithm provides a drastic improvement in the efficiency of data processing by replacing the slow process of manually identifying and deleting spurious data.

In situ X-ray diffraction investigation of electric-field-induced switching in a hybrid improper ferroelectric

This article reports the first in situ diffraction result collected under applied electric field on a hybrid improper ferroelectric which shows a subtle yet robust preference for a switching mechanism that proceeds via an unwinding of the octahedral rotation mode.

Small-angle neutron scattering measurements of mixtures of hydrogenous and deuterated n-tetra­decane

Small-angle neutron scattering of mixtures of hydrogenous and deuterated n-tetradecane, a typical linear n-alkane, can be used to determine the distribution of the molecules, in the same way as for mixtures of isotopically labeled polymers.

Polarization analysis for small-angle neutron scattering with a ³He spin filter at a pulsed neutron source

Neutron polarization analysis using a ³He spin filter for mainly soft matter systems is demonstrated for small-angle neutron scattering with a pulsed neutron source; successful separation of the coherent scattering component from the incoherent scattering component due to hydrogen atoms was achieved.

The effect of polydispersity, shape fluctuations and curvature on small unilamellar vesicle small-angle X-ray scattering curves

It is a challenge to distinguish the effect of shape fluctuations and size polydispersity on experimental small-angle X-ray scattering curves of small unilamellar vesicles. Here it is shown that both effects have distinguishable spectral patterns, and an efficient simulation tool is presented for simulating and analysing experimental data. The importance of curvature-induced electron-density profile asymmetry for estimating the vesicle size from SAXS scattering curves is also demonstrated.

Automated reconstruction of parent austenite phase based on the optimum orientation relationship

This work introduces a new approach to improve the current state of the art in prior austenite phase reconstruction in steels.

Numerically stable form factor of any polygon and polyhedron

Coordinate-free expressions for the form factors of arbitrary polygons and polyhedra are derived using the divergence theorem and Stokes's theorem. Series expansions are used to ensure numeric precision close to apparent singularities.

Laue X-ray diffraction studies of the structural perfection of Al-doped thermomigration channels in silicon

High-resolution X-ray Laue diffraction in an Si wafer patterned with vertically aligned Al-doped 100 µm-wide channels extending through the whole wafer was studied experimentally and simulated using the Takagi–Toupin dynamical diffraction theory. The calculated angular dependences of the intensities of both the diffracted and the transmitted X-ray beams corroborate the experimentally measured rocking curves and demonstrate their high sensitivity to the structural distortions in the channel.

2D real space visualization of d values in polycrystalline bulk materials of different hardness

A new imaging method to visualize differences of d values in the same sample has been applied to bulk steel materials. Some crystal grains are visible, and the strains caused by the Vickers mark are also quantitatively visualized.

The crystal structure and temperature dependence of the elpasolite Tl₂LiYCl₆

The room-temperature crystal structure of the elpasolite scintillator Tl₂LiYCl₆ was determined for the first time to be in the space group P4₂, and the evolution of the crystal structure up to 725 K was studied in detail, revealing a structural transition from P4₂ tetragonal to Fm3m cubic at 464 K.

Comparison and evaluation of pair distribution functions, using a similarity measure based on cross-correlation functions

A novel approach to the quantification of the agreement between pair distribution functions by a similarity measure based on cross-correlation functions is introduced and evaluated.

Distribution rules of systematic absences and generalized de Wolff figures of merit applied to electron backscatter diffraction ab initio indexing

A new method for electron backscatter diffraction ab initio indexing is reported. As a new sorting criterion for the solutions of Kikuchi-pattern indexing, generalized de Wolff figures of merit are also introduced.

New sample stage for characterizing radioactive materials by X-ray powder diffraction: application on five actinide dioxides ThO₂, UO₂, NpO₂, PuO₂ and AmO₂

A new sample stage dedicated to X-ray powder diffraction of actinide materials, and adaptable on a conventional Bragg–Brentano goniometer, is presented. This new experimental setup may also be used for the encapsulation of atmosphere-sensitive materials (not only radiotoxic samples).

Unifying the concepts of scattering and structure factor in ordered and disordered samples

This article reviews the core concepts of scattering and structure factor that are used to analyze structures of ordered and disordered samples. Simulations of scattering photography and intensity scanning of typical examples are provided, along with CPU and GPU source codes.

Validation of the Crystallography Open Database using the Crystallographic Information Framework

Data curation practices of the Crystallography Open Database are described with greater focus being placed on the cif_validate program, capable of validating crystallographic information files against both DDL1 and DDLm dictionaries.

Polo: an open-source graphical user interface for crystallization screening

A multi-platform open-source Python-based graphical user interface has been developed to provide access to automated classification and data management tools for biomolecular crystallization screening.

ipyChord: a package for evaluating small-angle X-ray scattering data of fiber symmetry

This work presents an open-source Python-based module for calculating the chord distribution function from the small-angle X-ray scattering pattern of polymer materials with fiber symmetry.

DATAD: a Python-based X-ray diffraction simulation code for arbitrary texture and arbitrary deformation

DATAD, a Python-based X-ray diffraction simulation code, has been developed for simulating one- and two-dimensional diffraction patterns of a polycrystalline specimen with an arbitrary texture under an arbitrary deformation state and an arbitrary detection geometry

MATSAS: a small-angle scattering computing tool for porous systems

MATSAS analyses X-ray and neutron small-angle scattering data obtained from porous systems. MATSAS delivers a full suite of pore characterizations, including specific surface area, porosity, pore size distribution and fractal dimensions.

Comment on the article The Cambridge Structural Database in chemical education: analysis of hydrogen-bonded networks in salts of hexa­aqua metal ions with organic counter-ions

A comment is made on the use of terms such as `low-dimensional structure'.

Dr H. Judith Milledge (née Grenville-Wells) (1927–2021)

International Tables for Crystallography, Volume H, Powder Diffraction

Principles of Neutron Scattering from Condensed Matter

The Science of Science