Experimental determination of the magnetic anisotropy in five-coordinated Co(ii) field-induced single molecule magnets.

Magnetic anisotropy of the central metal atom is a crucial property of single molecule magnets (SMMs). Small structural changes can alter the magnetic properties, and accurate experimental methods to investigate magnetic anisotropy are therefore critical. Here, we investigate two five-coordinated Co(ii) SMMs, [CoClCltpy] (1) and [CoBrCltpy] (2) (Cltpy = 4'-chloro-2,2':6',2''-terpyridine), through multiple techniques.

High-quality ultra-fast total scattering and pair distribution function data using an X-ray free-electron laser.

High-quality total scattering data, a key tool for understanding atomic-scale structure in disordered materials, require stable instrumentation and access to high momentum transfers. This is now routine at dedicated synchrotron instrumentation using high-energy X-ray beams, but it is very challenging to measure a total scattering dataset in less than a few microseconds. This limits their effectiveness for capturing structural changes that occur at the much faster timescales of atomic motion.

Unraveling the Crystal Structures of AgCh (Ch = S, Se, Te) via Simultaneous X-Ray Diffraction and Total Scattering.

Despite great interest in the properties of the AgCh (Ch = S, Se, Te) compounds, their complex crystal structures, envisioned as a disordered liquid-like Ag substructure, are poorly understood. This limits our understanding of the structural origin of their attractive properties. From combined powder X-ray diffraction (PXRD) and X-ray total scattering (TS) in the temperature range of 300-800 K, the average and local structures for all three AgCh compounds have been probed simultaneously for both the room-temperature (RT) and first high-temperature (HT) polymorphs.

Structural origins of ultralow glass-like thermal conductivity in AgGaGeSe.

Materials with low thermal conductivity are important for a variety of applications such as thermal barrier coatings and thermoelectrics, and understanding the underlying mechanisms of low heat transport, as well as relating them to structural features, remains a central goal within material science. Here, we report on the ultralow thermal conductivity of the quarternary crystalline silver chalcogenide AgGaGeSe, with a remarkable value of only 0.2 watts per meter per kelvin at room temperature and an unusual glass-like thermal behavior from 2 to 700 kelvin.

Benchmarking 3D-ΔPDF analysis using in-house X-ray sources.

New detector technology has in recent years improved the data quality available from in-house X-ray diffractometers. A recent study compared high-resolution low-temperature X-ray diffraction data obtained from modern in-house diffractometers with synchrotron data in relation to extracting subtle electron-density details using the multipole model [Vosegaard et al. (2023).

Near-Zero Thermal Expansion in Coordination Polymer Cd(1,2,4-Triazole)(HPO).

Zero thermal expansion is a rare but desirable physical property for materials. Here, we report an unprecedented near-zero thermal expansion (nZTE) behavior in a two-dimensional (2D) coordination polymer (CP) Cd(1,2,4-triazole) (HPO) (Cd-Tz) across a broad temperature range of 25 K-400 K. Using multi-temperature high-resolution single-crystal X-ray diffraction, we investigated the structural dynamics of the wine-rack-like framework of Cd-Tz and compared it with that of positive thermal expansion (PTE) CPs Zn-Tz and Mn-Tz with similar framework topology.

Reliability of pair distribution function analysis in experiments.

and pair distribution function (PDF) studies are becoming commonly used to study chemical reactions, nucleation and growth of nanoparticles, or structural changes during the operation of batteries, catalysts, thermoelectric devices However, repeated time-resolved total scattering experiments and subsequent PDF analysis are often not prioritized due to the scarce synchrotron beam time available. This means that the experimental uncertainty and reproducibility of the experimental methods are unknown, and the full potential of PDF experiments may not be exploited. Here, we quantify the experimental uncertainty of the PDF technique in an study of the hydro-thermal synthesis of ZrO nanoparticles.

Prediction and Validation of Mechanical Flexibility in Molecular Crystals: Dispersion Interactions Dictate Bending.

Mechanically flexible crystals are a rapidly growing class of functional molecular materials. Typically, such flexible crystals are discovered by serendipity. Herein, we have predicted mechanical flexibility in a series of molecular crystals based on a structure screening approach that combines interaction topology and the presence of nitrile···nitrile interactions-a supramolecular motif hitherto not associated with bending property.

The effect of second coordination sphere interactions on the magnetic anisotropy of transition metals.

In the study of mononuclear transition metal single molecule magnets (SMMs), extensive research has concentrated on identifying optimal coordination geometries around the central metal ion to enhance SMM properties. However, the role of non-covalent interactions in the second coordination sphere has been relatively underexplored. Here, we study the impact of non-covalent Cl⋯H interactions on the magnetic anisotropy of the central Co(II) ion in the distorted axially compressed octahedral complex CoCl(tu) (1) (tu = SC(NH)).

Synthesis and characterization of an organic-inorganic hybrid crystal: 2[Co(en)](VO)·4HO.

Organic-inorganic hybrid crystals have diverse functionalities, for example in energy storage and luminescence, due to their versatile structures. The synthesis and structural characterization of a new cobalt-vanadium-containing compound, 2[Co(en)](VO)·4HO (1) is presented. The crystal structure of 1, consisting of [Co(en)] complexes and chains of corner-sharing (VO) tetrahedra, was solved by single-crystal X-ray diffraction in the centrosymmetric space group P1.

Formation Mechanism and Hydrothermal Synthesis of Highly Active IrRuO Nanoparticles for the Oxygen Evolution Reaction.

Iridium dioxide (IrO), ruthenium dioxide (RuO), and their solid solutions (IrRuO) are very active electrocatalysts for the oxygen evolution reaction (OER). Efficient and facile synthesis of nanosized crystallites of these materials is of high significance for electrocatalytic applications for converting green energy to fuels (power-to-X). Here, we use X-ray scattering to examine reaction conditions for different Ir and Ru precursors resulting in the development of a simple hydrothermal synthesis route using IrCl and KRuO to obtain homogeneous phase-pure IrRuO nanocrystals.

Continuous-Flow Synthesis of ZnMnS Nanoparticles at Ambient Conditions.

With its large direct band gap and good chemical stability, ZnS is suitable for many applications, including light-emitting diodes, panel displays, and photodetection. Here, nanoparticles of ZnS are synthesized phase pure under ambient conditions by precipitation in a simple and scalable continuous-flow reactor. Furthermore, different degrees of Zn substitution with Mn have been investigated, ZnMnS, with = 0.

Exploration of anion effects in solvothermal synthesis using X-ray diffraction.

Solvothermal synthesis presents a facile and highly flexible approach to chemical processing and it is widely used for preparation of micro- and nanosized inorganic materials. The large number of synthesis parameters in combination with the richness of inorganic chemistry means that it is difficult to predict or design synthesis outcomes, and it is demanding to uncover the effect of different parameters due to the sealed and complex nature of solvothermal reactors along with the time demands related to reactor cleaning, sample purification, and characterization. This study explores the effect on formation of crystalline products of six common anions in solvothermal treatment of aqueous and ethanolic precursors.

Stabilizing tetragonal ZrO nanocrystallites in solvothermal synthesis.

Phase-pure tetragonal ZrO nanoparticles have been prepared under simple solvothermal synthesis conditions using different types of alcohols as solvents and studied using X-ray scattering. The variation of tetragonal/monoclinic phase ratios within the produced powders was directly correlated with the amount of generated water from solvent dehydration during the syntheses. By controlling the dehydration kinetics, either choosing primary alcohols of varying thermal stability or by changing synthesis temperatures, it is possible to selectively tune this tetragonal/monoclinic phase ratio.

Refining short-range order parameters from the three-dimensional diffuse scattering in single-crystal electron diffraction data.

Our study compares short-range order parameters refined from the diffuse scattering in single-crystal X-ray and single-crystal electron diffraction data. NbCoSb was chosen as a reference material. The correlations between neighbouring vacancies and the displacements of Sb and Co atoms were refined from the diffuse scattering using a Monte Carlo refinement in DISCUS.

Unveiling the formation mechanism of PbPd intermetallic phases in solvothermal synthesis using X-ray total scattering.

Pd possesses attractive catalytic properties and nano-structuring is an obvious way to enhance catalytic activity. Alloying Pd with Pb has been shown to enhance the catalytic effect of alcohol oxidation. Further optimization of the catalytic effect can be accomplished by controlling the particle size and key to this is understanding the formation mechanism.

The Ambiguous Origin of Thermochromism in Molecular Crystals of Dichalcogenides: Chalcogen Bonds versus Dynamic Se-Se/Te-Te Bonds.

We report thermochromism in crystals of diphenyl diselenide (dpdSe) and diphenyl ditelluride (dpdTe), which is at variance with the commonly known mechanisms of thermochromism in molecular crystals. Variable temperature neutron diffraction studies indicated no conformational change, tautomerization or phase transition between 100 K and 295 K. High-pressure crystallography studies indicated no associated piezochromism in dpdSe and dpdTe crystals.

Benchmark Crystal Structure of Defect-Free Spinel ZnFeO.

Accurate structural models are of paramount importance for elucidating structure-property relationships in functional materials. Spinels (ABO) form a highly important family of materials with complex crystal structures, and subtle structural details have a critical bearing on understanding their physical properties. In some spinels, the space group symmetry is debated, and in general, point defects such as cation inversion and interstitials add complexity.

Pair Distribution Function from Liquid Jet Nanoparticle Suspension using Femtosecond X-ray Pulses.

X-ray scattering data measured on femtosecond timescales at the SACLA X-ray Free Electron Laser (XFEL) facility on a suspension of HfO nanoparticles in a liquid jet were used for pair distribution function (PDF) analysis. Despite a non-optimal experimental setup resulting in a modest Q of ~8 Å , a promising PDF was obtained. The main features were reproduced when comparing the XFEL PDF to a PDF obtained from data measured at the PETRA III synchrotron light source.

Comparative study of conventional and synchrotron X-ray electron densities on molecular crystals.

Five different electron density datasets obtained from conventional and synchrotron single crystal X-ray diffraction experiments are compared. The general aim of the study is to investigate the quality of data for electron density analysis from current state-of-the-art conventional sources, and to see how the data perform in comparison with high-quality synchrotron data. A molecular crystal of melamine was selected as the test compound due to its ability to form excellent single crystals, the light atom content, and an advantageous suitability factor of 3.

A reactor for time-resolved X-ray studies of nucleation and growth during solvothermal synthesis.

Understanding the nucleation and growth mechanisms of nanocrystals under hydro- and solvothermal conditions is key to tailoring functional nanomaterials. High-energy and high-flux synchrotron radiation is ideal for characterization by powder X-ray diffraction and X-ray total scattering in real time. Different versions of batch-type cell reactors have been employed in this work, exploiting the robustness of polyimide-coated fused quartz tubes with an inner diameter of 0.

X-ray diffraction study of the solvothermal formation mechanism of gallium oxide nanoparticles.

Gallium oxides are of broad interest due to their wide band gaps and attractive photoelectric properties. Typically, the synthesis of gallium oxide nanoparticles is based on a combination of solvent-based methods and subsequent calcination, but detailed information about solvent based formation processes is lacking, and this limits the tailoring of materials. Here we have examined the formation mechanisms and crystal structure transformations of gallium oxides during solvothermal synthesis using X-ray diffraction.

Dynamic Lone Pair Expression as Chemical Bonding Origin of Giant Phonon Anharmonicity in Thermoelectric InTe.

Loosely bonded ("rattling") atoms with s lone pair electrons are usually associated with strong anharmonicity and unexpectedly low thermal conductivity, yet their detailed correlation remains largely unknown. Here we resolve this correlation in thermoelectric InTe by combining chemical bonding analysis, inelastic X-ray and neutron scattering, and first principles phonon calculations. We successfully probe soft low-lying transverse phonons dominated by large In z-axis motions, and their giant anharmonicity.

A Machine-Learning-Based Approach for Solving Atomic Structures of Nanomaterials Combining Pair Distribution Functions with Density Functional Theory.

Determination of crystal structures of nanocrystalline or amorphous compounds is a great challenge in solid-state chemistry and physics. Pair distribution function (PDF) analysis of X-ray or neutron total scattering data has proven to be a key element in tackling this challenge. However, in most cases, a reliable structural motif is needed as a starting configuration for structure refinements.

Towards pump-probe single-crystal XFEL refinements for small-unit-cell systems.

Serial femtosecond crystallography for small-unit-cell systems has so far seen very limited application despite obvious scientific possibilities. This is because reliable data reduction has not been available for these challenging systems. In particular, important intensity corrections such as the partiality correction critically rely on accurate determination of the crystal orientation, which is complicated by the low number of diffraction spots for small-unit-cell crystals.