Many scientific questions require X-ray experiments conducted at varying temperatures, sometimes combined with the application of electric fields. Here, a customized sample chamber developed for beamlines P23 and P24 of PETRA III at DESY to suit these demands is presented. The chamber body consists mainly of standard vacuum parts housing the heater/cooler assembly supplying a temperature range of 100 K to 1250 K and an xyz manipulator holding an electric contact needle for electric measurements at both high voltage and low current. The chamber is closed by an exchangeable hemispherical dome offering all degrees of freedom for single-crystal experiments within one hemisphere of solid angle. The currently available dome materials (PC, PS, PEEK polymers) differ in their absorption and scattering characteristics, with PEEK providing the best overall performance. The article further describes heating and cooling capabilities, electric characteristics, and plans for future upgrades of the chamber. Examples of applications are discussed.

Hafnium Zirconium Oxide Hf x Zr1-x O2 is a potentially ferroelectric material with great perspectives in semiconductor applications, due to its compatibility with silicon technologies and its low toxicity. Despite its chemical simplicity, the solid solution Hf x Zr1-x O2 comprises a large variety of different phases. We compiled a complete list of experimentally and theoretically reported Hf x Zr1-x O2 structures. All of them are symmetrically related to the common aristotype with Fluorite type structure. The symmetry relationships between those structures have been determined and are presented in a Barnighausen-like tree. Interestingly, not all symmetry reductions follow the conventional group-subgroup relations and involve severe atomic shifts. Further, the structures were compared to each other in detail regarding the dimensionality of atomic shifts and the accompanied lattice distortions. Finally, the information provided by the Barnighausen-like tree was used to transform the indices of a reflection before and after a phase transition. This conversion allows the study of (dis)appearing reflections during phase transitions.

During X-ray diffraction experiments on single crystals, the diffracted beam intensities may be affected by multiple-beam X-ray diffraction (MBD). This effect is particularly frequent at higher X-ray energies and for larger unit cells. The appearance of this so-called Renninger effect often impairs the interpretation of diffracted intensities. This applies in particular to energy spectra analysed in resonant experiments, since during scans of the incident photon energy these conditions are necessarily met for specific X-ray energies. This effect can be addressed by carefully avoiding multiple-beam reflection conditions at a given X-ray energy and a given position in reciprocal space. However, areas which are (nearly) free of MBD are not always available. This article presents a universal concept of data acquisition and post-processing for resonant X-ray diffraction experiments. Our concept facilitates the reliable determination of kinematic (MBD-free) resonant diffraction intensities even at relatively high energies which, in turn, enables the study of higher absorption edges. This way, the applicability of resonant diffraction, e.g. to reveal the local atomic and electronic structure or chemical environment, is extended for a vast majority of crystalline materials. The potential of this approach compared with conventional data reduction is demonstrated by the measurements of the Ta L ₃ edge of well studied lithium tantalate LiTaO₃.

The Parameter Space Concept (PSC) is an alternative approach to solving and refining (partial) crystal structures from very few pre-chosen X-ray or neutron diffraction amplitudes without the use of Fourier inversion. PSC interprets those amplitudes as piecewise analytic hyper-surfaces, so-called isosurfaces, in the Parameter Space, which is spanned by the spatial coordinates of all atoms of interest. The intersections of all isosurfaces constitute the (possibly degenerate) structure solution. The present feasibility study investigates the La and Sr split position of the potential high-temperature super-conductor (La_0.5Sr_1.5)MnO₄, $I4$/mmm, with a postulated total displacement between La and Sr of a few $\mathrm{p}$$\mathrm{m}$ by theoretical amplitudes of pre-selected $00l$ reflections ($l=2,4,\dots ,20$). The revision of 15-year-old results with state-of-the-art computing equipment enhances the former simplified model by varying the scattering power ratio $f_{\begin{array}{c}\hfill \mathrm{La}\end{array}}/f_{\begin{array}{c}\hfill \mathrm{Sr}\end{array}}$, as exploitable by means of resonant scattering contrast at synchrotron facilities, and irrevocably reveals one of the two originally proposed solutions as being a “blurred” pseudo-solution. Finally, studying the resolution limits of PSC as a function of intensity errors by means of Monte-Carlo simulations shows both that the split can only be resolved for sufficiently low errors and, particularly for the resonant scattering contrast, a theoretical precision down to $\pm 0.19$ $\mathrm{p}$$\mathrm{m}$ can be achieved for this specific structural problem.

The Photon and Neutron Experimental Techniques (PaNET) ontology was released in 2021 as an ontology for two major European research infrastructure communities. It provides a standardized taxonomy of experimental techniques employed across the photon and neutron scientific domain, and is part of a wider effort to apply the FAIR (findable, accessible, interoperable, reusable) principles within the community. Specifically, it is used to enhance the quality of metadata in photon and neutron data catalogue services. However, PaNET currently relies on a manual definition approach, which is time consuming and incomplete. A new structure of PaNET is proposed to address this by including logical frameworks that enable automatic reasoning as opposed to the manual approach in the original ontology, resulting in over a hundred new technique subclass relationships that are currently missing in PaNET. These new relationships, which are evaluated by the PaNET working group and other domain experts, will improve data catalogue searches by connecting users to more relevant datasets, thereby enhancing data discoverability. In addition, the results of this work serve as a validation mechanism for PaNET, as the very process of building the logical frameworks, as well as any incorrect inferences made by the reasoner, has exposed existing issues within the original ontology.

We present the elaboration and first generally applicable linearization routines of the parameter space concept (PSC) for determining one-dimensionally projected structures of m independent scatterers. This crystal determination approach does not rely on Fourier inversion but rather considers all structure parameter combinations consistent with available diffraction data in a parameter space of dimension m . The method utilizes m structure-factor amplitudes or intensities represented by piecewise analytic hyper-surfaces to define the acceptable parameter regions. The coordinates of the point scatterers are obtained through the intersection of multiple isosurfaces. This approach allows for the detection of all possible solutions for the given structure-factor amplitudes in a single derivation. Taking the resonant contrast into account, the spatial resolution achieved by the presented method may exceed that of traditional Fourier inversion, and the algorithms can be significantly optimized by exploiting the symmetry properties of the isosurfaces. The applied one-dimensional projection demonstrates the efficiency of the PSC linearization approach based on fewer reflections than Fourier sums. Monte Carlo simulations, using the projections of various random two- and three-atom structure examples, are presented to illustrate the universal applicability of the proposed method. Furthermore, ongoing efforts aim to enhance the efficiency of data handling and to overcome current constraints, promising further advancements in the capabilities and accuracy of the PSC framework.