Journal of Applied Crystallography

Ekeberg, Tomas

doi: 10.1107/s1600576723010476pmid: 38322721

Artificial intelligence is more present than ever, both in our society in general and in science. At the center of this development has been the concept of deep learning, the use of artificial neural networks that are many layers deep and can often reproduce human‐like behavior much better than other machine‐learning techniques. The articles in this collection are some recent examples of its application for X‐ray photon science and crystallography that have been published in Journal of Applied Crystallography.

Rowenhorst, David J.; Callahan, Patrick G.; Ånes, Håkon W.

doi: 10.1107/s1600576723010221pmid: N/A

The automated indexing and orientation determination of backscattered Kikuchi patterns is an essential step in electron backscattered diffraction (EBSD) analysis. Here a new Radon‐transform‐based algorithm is developed within the software package PyEBSDIndex, which features a number of key improvements over what has been traditionally available. The Radon convolutions use derivatives of Gaussian kernels that more closely match EBSD band profiles, which is combined with sub‐pixel localization of the peaks in the Radon transform. Additionally, the weighted quaternion estimator algorithm (QUEST) is leveraged to provide the final estimation of the crystal orientation. The combination of these techniques allows for high‐accuracy indexing and precise orientation determination, with tests on simulated patterns showing mean orientation errors as low as 0.037° and a 95% confidence level of 0.073°. Additional testing of the effect of pattern noise shows that PyEBSDIndex performs similarly to the spherical harmonic transform indexing methods except in the most extreme levels of low pattern quality. A test case of indexing a dual‐phase Ti‐6Al‐4V EBSD map finds that PyEBSDIndex differentiates phases equivalently to the commercial Hough indexing solution, with orientation noise 75% lower than the commercial solution. Finally, it is shown that PyEBSDIndex, by performing the image processing calculations on the GPU, is able to analyze patterns at unprecedented speeds, in some cases at over 45 000 patterns s−1, thereby providing sufficient speed for newer, high‐speed detectors. PyEBSDIndex is open source and available at https://github.com/USNavalResearchLaboratory/PyEBSDIndex.

Nagle-Cocco, Liam. A. V.; Dutton, Siân E.

doi: 10.1107/s1600576723009925pmid: 38322718

Van Vleck modes describe all possible displacements of octahedrally coordinated ligands about a core atom. They are a useful analytical tool for analysing the distortion of octahedra, particularly for first‐order Jahn–Teller distortions, but determination of the Van Vleck modes of an octahedron is complicated by the presence of angular distortion of the octahedron. This problem is most commonly resolved by calculating the bond distortion modes (Q2, Q3) along the bond axes of the octahedron, disregarding the angular distortion and losing information on the octahedral shear modes (Q4, Q5 and Q6) in the process. In this paper, the validity of assuming bond lengths to be orthogonal in order to calculate the Van Vleck modes is discussed, and a method is described for calculating Van Vleck modes without disregarding the angular distortion. A Python package for doing this, VanVleckCalculator, is introduced and some examples of its use are given. Finally, it is shown that octahedral shear and angular distortion are often, but not always, correlated, and a parameter η is proposed as the shear fraction. It is demonstrated that η can be used to predict whether the values will be correlated when varying a tuning parameter such as temperature or pressure.

Anker, Andy S.; Kjær, Emil T. S.; Juelsholt, Mikkel; Jensen, Kirsten M. Ø.

doi: 10.1107/s1600576723010014pmid: 38322723

Characterization of a material structure with pair distribution function (PDF) analysis typically involves refining a structure model against an experimental data set, but finding or constructing a suitable atomic model for PDF modelling can be an extremely labour‐intensive task, requiring carefully browsing through large numbers of possible models. Presented here is POMFinder, a machine learning (ML) classifier that rapidly screens a database of structures, here polyoxometallate (POM) clusters, to identify candidate structures for PDF data modelling. The approach is shown to identify suitable POMs from experimental data, including in situ data collected with fast acquisition times. This automated approach has significant potential for identifying suitable models for structure refinement to extract quantitative structural parameters in materials chemistry research. POMFinder is open source and user friendly, making it accessible to those without prior ML knowledge. It is also demonstrated that POMFinder offers a promising modelling framework for combined modelling of multiple scattering techniques.

Sasso, Carlo P.; Mana, Giovanni; Massa, Enrico

doi: 10.1107/s1600576723010245pmid: 38322716

The observation of neutron interference using a triple Laue interferometer formed by two separate crystals opens the way to the construction and operation of skew‐symmetric interferometers with extended arm separation and length. The specifications necessary for their successful operation are investigated here: most importantly, how the manufacturing tolerance and crystal alignments impact the interference visibility. In contrast with previous studies, both incoherent sources and the three‐dimensional operation of the interferometer are considered. It is found that, with a Gaussian Schell model of an incoherent source, the integrated density of the particles leaving the interferometer is the same as that yielded by a coherent Gaussian source having a radius equal to the coherence length.

Hammarberg, Susanna; Dzhigaev, Dmitry; Marçal, Lucas A. B.; Dagytė, Vilgailė; Björling, Alexander; Borgström, Magnus T.; Wallentin, Jesper

doi: 10.1107/s1600576723010403pmid: 38322717

Developing semiconductor devices requires a fast and reliable source of strain information with high spatial resolution and strain sensitivity. This work investigates the strain in an axially heterostructured 180 nm‐diameter GaInP nanowire with InP segments of varying lengths down to 9 nm, simultaneously probing both materials. Scanning X‐ray diffraction (XRD) is compared with Bragg projection ptychography (BPP), a fast single‐projection method. BPP offers a sufficient spatial resolution to reveal fine details within the largest segments, unlike scanning XRD. The spatial resolution affects the quantitative accuracy of the strain maps, where BPP shows much‐improved agreement with an elastic 3D finite element model compared with scanning XRD. The sensitivity of BPP to small deviations from the Bragg condition is systematically investigated. The experimental confirmation of the model suggests that the large lattice mismatch of 1.52% is accommodated without defects.

Hwang, Shyh-Lung; Shen, Pouyan; Yui, Tzen-Fu; Chu, Hao-Tsu; Usui, Yoichi

doi: 10.1107/s160057672301004xpmid: N/A

The correct and precise crystal forms and the crystallographic orientation relationships (CORs) of ten main magnetite needle groups in the plagioclase host were unequivocally determined by transmission electron microscopy from >100 selected magnetite needles with well defined shape orientations in petrographic thin sections of a gabbro core sample drilled from the Mid‐Atlantic Ridge. The as‐observed CORs of magnetite in plagioclase are in accordance with the optimal matching in the oxygen sublattices of the two structures via the close alignment between two sets of close‐packed (c.p.) oxygen arrays parallel to {111}m in magnetite (m) and two sets of quasi‐c.p. oxygen arrays parallel to (150)p, (150)p, (112)p, (312)p, (021)p or (121)p in plagioclase (p), as demonstrated for the first time in the accumulated oxygen number versus normal distance [from the (hkl) plane] plots. Such a simple oxygen sublattice matching principle does not rely on the length matching for the specific pair of lattice directions or on the d‐spacing matching for the specific pair of lattice planes of the two structures, and therefore must be generally applicable for any mineral/oxide inclusions with a c.p. or quasi‐c.p. oxygen sublattice formed via precipitation in open or closed systems. The topotaxial nuclei then undergo extended growth along the kinetically fast growth direction of the two structures with the most similar oxygen distribution patterns, i.e. along the normal direction of the aligned pair of oxygen arrays, thereby yielding the pronounced shape orientations such as magnetite needles in plagioclase.

Hu, Danrui; Beauvais, Michelle L.; Mullens, Bryce G.; Sanchez Monserrate, Bryan A.; Vornholt, Simon M.; Kamm, Gabrielle E.; Ferrari, John J.; Chupas, Peter J.; Chapman, Karena W.

doi: 10.1107/s1600576723011020pmid: N/A

In situ X‐ray scattering provides valuable insights into the mechanisms and kinetics of reactions and structural transformations. For reactions and structural transformations primarily driven by temperature, and not coupled to chemical/electrochemical triggers, our ability to initiate and quench processes thermally is a practical limit for probing fast reactive phenomena. Meaningful quantitative analysis requires the dynamic phenomena to be triggered on fast time scales relative to the reaction/transformation kinetics. This article describes a new sample furnace, the Rapid‐Actuating Pneumatic Thermal Reactor or RAPTR, for time‐resolved in situ X‐ray scattering studies initiated by temperature. The RAPTR quickly heats and cools samples by translating them into and out of a pre‐heated hot zone. Using diffraction thermometry, it is shown that the samples can be heated/cooled in 10 s or less, with temperatures up to ∼1000°C being accessible. The application of the RAPTR furnace is demonstrated by exploring a fast solid‐state reaction: the synthesis of scheelite‐type lead tungstate, PbWO4, from PbO and WO3 for which Pb3WO6 is identified as a previously unrecognized reaction intermediate.

Sepsi, Mate; Benke, Marton; Mertinger, Valeria

doi: 10.1107/s1600576723010993pmid: N/A

The most common methods for texture characterization require cutting a coupon to be inserted into an X‐ray texture goniometer or an electron microscope and are, therefore, destructive. However, there are many cases where texture characterization needs to be performed in a non‐destructive way, where the measurement can be made without damaging the object. Typical examples are archaeological artefacts or very expensive materials. Here we demonstrate the application of an X‐ray diffractometer mounted on a robotic arm designed for residual stress scanning for texture characterization, enabling the determination of the orientation distribution function for different locations on samples with complex geometries. The texture characterization method was benchmarked on a cold‐rolled aluminium sheet.

Dyk, Konrad; Kinzhybalo, Vasyl; Horak, Yuriy; Butenko, Serhii; Siczek, Miłosz; Kamiński, Daniel M.

doi: 10.1107/s1600576723010609pmid: N/A

This paper investigates the structural properties of 2,5‐bis(3‐bromophenyl)furan polymorphs, focusing on the halogen interactions and their influence on crystal mechanical properties. In this study, three different polymorphic modifications were obtained which crystallize in the orthorhombic system. Two of the polymorphs possess halogen interactions but only one exhibits elastic properties. Through X‐ray diffraction, crystallographic analysis and computational modelling, intricate bromine‐based halogen interactions and their impact on the packing arrangement and stability were revealed. The correlation between these interactions and crystal properties, including molecular arrangement and intermolecular forces, is explored. Understanding these relationships is vital for materials design and supramolecular chemistry, enabling the rational synthesis of tailored materials.