Journal of Applied Crystallography最新文献

Serial crystallography for time-resolved structural studies of light-triggered reactions often employs high-viscosity jets to deliver crystals into an X-ray beam. A potential complication is that pump light can scatter within the jet to unintentionally irradiate yet-to-be-probed portions of the jet - a problem known as light contamination. Importantly, by transporting light out of the nominal interaction region, light scattering can reduce the effective irradiation energy density experienced by the diffracting crystal. This issue, which can even jeopardize an experiment, has proven rather controversial. To provide direct insight, we performed custom femtosecond transient absorption experiments with spatially displaced pump and probe beams directed onto actual jets under realistic experimental conditions, allowing the distribution of excited molecules along the flowing jet to be mapped out explicitly. To characterize the underlying light scattering properties of commonly used jet media, the Kubelka-Munk formalism was utilized. Our results show that, in contrast to flat-cell geometries, which we found to exhibit minimal light contamination, the cylindrical geometry of jets can facilitate a degree of light spill-over. The excitation energy density loss due to the scattering is less than 30% in realistic experimental conditions. This highlights the importance of carefully selecting jet media and laser parameters to minimize light-scattering-induced artefacts when undertaking pump-probe serial crystallography experiments.

We are involved in designing, constructing and operating a split-crystal interferometer that uses X-rays and neutrons simultaneously. Neutron interferometers are sensitive to seismic and acoustic noise due to the low speed, low flux and long detection time of thermal neutrons. The crystal splitting and the increased length and separation of the interferometer arms further heighten this sensitivity. To support the interferometer design and operation, we present an estimate of the root-mean-square phase noise when the interferometer is passively isolated from ground accelerations.

Understanding the dynamic and structural properties of matter across different timescales and length scales is essential for elucidating their functionality. We focus here on soft-matter systems, which are typically particularly sensitive to relative humidity (RH) and temperature, necessitating well controlled experimental conditions. Quasi-elastic neutron scattering (QENS) and Raman spectroscopy offer complementary insights: QENS accesses diffusional dynamics, which are stochastic motions, while Raman spectroscopy provides information on periodic vibrational dynamics. To enable simultaneous QENS and Raman measurements on e.g. polymer films under controlled and variable RH and temperature, we have developed a dedicated sample environment (SE), which in the presented experiments covers an RH range of 5-85% and a temperature range of 20-50°C. This SE features a 3D-printed spherical chamber including a sample holder for films, a Raman spectrometer, a custom-built gas-flow system and a thermostat. The chamber can accommodate large samples (up to 5 × 5 cm) and provides space for additional measurement equipment. The 3D-printing technique allows the integration of channels into the chamber walls, which are used for cooling and heating, resulting in highly homogeneous temperature distributions. This is key to achieving a uniform humidity in the chamber. The chamber works with a variety of solvents and their mixtures, like heavy water or ethanol. We demonstrate the feasibility of this setup through simultaneous QENS and Raman measurements on poly(3,4-ethylene di-oxy-thio-phene):poly(styrene-sulfonate) films on Si substrates, confirming that the chamber provides a stable and low scattering background environment.

Small-angle X-ray scattering (SAXS) experiments performed at synchrotron radiation sources enable the in situ study of precipitation behaviour, providing crucial information for alloy design. Numerous studies have demonstrated the successful use of SAXS to investigate precipitation phenomena across a wide range of complex metallic systems. Nevertheless, despite its advantages, the application of SAXS remains often overlooked owing to the challenges associated with data analysis, especially under non-isothermal conditions in which a metal matrix is continuously evolving due to simultaneous phase transformations and microstructural coarsening. This work presents a novel SAXS modelling approach developed for the quantitative evaluation of precipitate formation in metallic systems exhibiting scattering signals superimposed on directionally streaked signals originating from the embedding matrix, as commonly found in martensitic microstructures. Two-dimensional synchrotron data recorded during a continuous in situ heating experiment on a Cu- and Si-containing near-α Ti alloy are used to demonstrate how the evolving SAXS signal can be separated into matrix- and precipitation-related contributions. A Guinier-Porod function linked to a grain coarsening model was used to describe the background signal from the matrix, while Ti₂Cu precipitates were modelled using an ellipsoidal model function combined with a lognormal size distribution. This combined approach enabled the evaluation of precipitate volume fraction and size distribution throughout the heat treatment. The SAXS results were validated through complementary transmission electron microscopy and atom probe tomography experiments, showing excellent agreement in both size and phase fraction. The presented methodology allows the successful capture of early-stage precipitation and provides an adaptable solution to background modelling challenges in non-isothermal SAXS experiments. This approach expands the applicability of SAXS for precipitation studies in structurally complex alloy systems.

[This corrects the article DOI: 10.1107/S1600576723001036.].

We employ a combined computational and experimental approach to systematically assess the hydrostatic properties of methanol-ethanol (MeOH-EtOH) mixtures of varying compositions, with the aim of evaluating their suitability as pressure-transmitting mediums (PTMs). PTMs are essential for enabling the characterization of materials properties at high pressure, perhaps most prominently in the context of diffraction measurements, to provide uniform compression and avoid strain on the sample. Molecular dynamics (MD) simulations indicate that the hydrostatic limit and several structural and dynamic properties of the widely used 4:1 MeOH-EtOH volume ratio do not exhibit any significant deviations from the monotonic trends observed as a function of MeOH content within the mixture. These findings are in agreement with X-ray pair distribution function measurements, which show no peculiar structural behaviour for the 4:1 composition. Experimental measurements of the hydrostatic limit confirm this result and demonstrate that, as previously reported, the role of ethanol is primarily to delay MeOH crystallization. However, we find that the same role can be fulfilled by other small molecules, such as propan-2-ol. Additional simulations of several MeOH-X binary mixtures suggest that these results might hold for a variety of similar mixtures. Thus, our findings indicate that the 4:1 ratio is neither peculiar nor optimal in terms of PTM performance; instead, its popularity seems to be mostly due to the influence of previous literature. Indeed, we find that the 9:1 MeOH-EtOH mixture is characterized by a hydrostatic limit which is superior (by nearly 1 GPa) to that observed for the 4:1 ratio. These findings offer a promising alternative PTM composition which is readily available, and pave the way towards future work aimed at the rational design of novel PTMs.

Three-dimensional electron diffraction (3D ED) has emerged as a powerful tool for solving the structures of small crystals down to nanometre-scale sizes. Despite advancements in automating data acquisition for 3D ED, the subsequent data processing and structure solution have largely relied on human intervention and have been mostly conducted offline. This reliance on expertise in electron crystallography and the lack of real-time feedback on data quality and structural information have limited the broader adoption of 3D ED. Here, we introduce Instamatic-solve, a fully automated, real-time structure solution pipeline for 3D ED deployed on a JEOL JEM 2100 transmission electron microscope. Instamatic-solve streamlines the entire process by automating the subsequent data processing and structure solution, providing real-time assessments of data quality and structural information. Moreover, the pipeline can handle offline 3D ED data acquired from various transmission electron microscope platforms. Using Instamatic-solve, we have successfully solved the crystal structures of diverse materials, including seven inorganic zeolites, two inorganic-organic hybrids and four organic molecules (including pharmaceuticals), all within 2 min. Instamatic-solve mimics the typical manual structure solution process, and its outcomes depend heavily on data quality. Our results indicate that a routine and reliable structure solution is achievable in most cases, provided that the data meet critical quality criteria, namely completeness ≥50% and resolution better than 1.0 Å. By enabling efficient, automated and real-time structure solution for crystalline materials, Instamatic-solve spans various scientific disciplines.

Structural characterization of nanoscale two-metal-phase systems, which exhibit partial, complete or no mixing when co-sputtered with a few percent of a minority element, is extremely challenging. Co-sputtering two metals at room temperature results in frozen disorder within the deposited films. Distinguishing the contribution of each metal phase, determining the distribution and self-organization of the second constituent element within the Cu matrix, accurately quantifying the extra element content, and assessing internal disorder through diffraction analysis are complex and require the development of a suitable model to fit diffraction patterns from various geometries. Here, we present a model to describe the structural distribution of alloy elements in magnetron-sputtered Cu thin films, exploring two contrasting cases: (1) with the mutually immiscible Nb and (2) with Pd, which has a negative heat of mixing with Cu, forming stable alloys. A comparison between X-ray diffraction data and energy-dispersive X-ray spectroscopy derived elemental distribution is discussed.

Sample and diffractometer alignment for grazing-incidence X-ray measurements become ever more crucial once the beam and surface area of interest reach the nanometre scale. Here we show how a point of interest on a surface can be kept in the beam while measuring X-ray reflectivity, even if it is not in the centre of rotation, either because of systematic errors or additional unwanted angle-dependent sample movement. This can be achieved by a 1D trajectory scan varying the angle of incidence (θ), the detector angle (2θ) and the position of the sample along one axis in the scattering plane. As an example, we show the results of X-ray reflectivity measured from a 10 × 10 µm Au island using a 90 nm beam. Data analysis is presented which considers the angle-dependent X-ray beam footprint illuminating both the Au island and the surrounding support.

Understanding the grain morphology, orientation distribution and crystal structure of nanocrystals is essential for optimizing the mechanical and physical properties of functional materials. Synchrotron X-ray Laue microdiffraction is a powerful technique for characterizing crystal structures and orientation mapping using focused X-rays. However, when the grain sizes are smaller than the beam size, mixed peaks in the Laue pattern from neighboring grains limit the resolution of grain morphology mapping. We propose a physics-informed machine learning (PIML) approach that combines a convolutional neural network feature extractor with a physics-informed filtering algorithm to overcome the spatial resolution limits of X-rays, achieving nanoscale resolution for grain mapping. Our PIML method successfully resolves the grain size, orientation distribution and morphology of Au nanocrystals through synchrotron microdiffraction scans, showing good agreement with electron backscatter diffraction results. This PIML-assisted synchrotron microdiffraction analysis can be generalized to other diffraction-based probes, enabling the characterization of nanosized structures with micrometre-sized probes.