Controlling the magnetic structure in W-type hexaferrites.

W-type hexaferrites with varied Co/Zn ratios were synthesized and the magnetic order was investigated using neutron powder diffraction. In SrCoFeO and SrCoZnFeO a planar ('') magnetic ordering was found, rather than the uniaxial ordering (6/'') found in SrZnFeO which is common in most W-type hexaferrites. In all three studied samples, non-collinear terms were present in the magnetic ordering.

Halogen Bond Induced Structural and Photophysical Properties Modification in Organic-Inorganic Hybrid Manganese Halides.

The role of halogen bonding in organic-inorganic hybrid (OIH) halides was seldom investigated despite its potential to enhance the stability of the compound. In this context, we have synthesized (2-methylbenzimidazolium)MnCl(HO)·HO (compound 1) crystallizing in a monoclinic space group 2/ with a 1D infinite chain of edge shared Mn octahedra. In contrast, the chloro-substituted derivative (5-chloro-2-methylbenzimidazolium)MnCl (compound 2) exhibits 0D Mn tetrahedra with a triclinic 1̅ structure.

On single-crystal total scattering data reduction and correction protocols for analysis in direct space. Corrigendum.

The name of the third author of the article by Koch et al. [Acta Cryst. (2021).

In-depth investigations of size and occupancies in cobalt ferrite nanoparticles by joint Rietveld refinements of X-ray and neutron powder diffraction data.

Powder X-ray diffraction (PXRD) and neutron powder diffraction (NPD) have been used to investigate the crystal structure of CoFeO nanoparticles prepared different hydro-thermal synthesis routes, with particular attention given to accurately determining the spinel inversion degrees. The study is divided into four parts. In the first part, the investigations focus on the influence of using different diffraction pattern combinations (NPD, Cu-source PXRD and Co-source PXRD) for the structural modelling.

X-ray Electron Density Study of the Chemical Bonding Origin of Glass Formation in Metal-Organic Frameworks.

Glass-forming metal-organic frameworks (MOFs) have novel applications, but the origin of their peculiar melting behavior is unclear. Here, we report synchrotron X-ray diffraction electron densities of two zeolitic imidazolate frameworks (ZIFs), the glass-forming Zn-ZIF-zni and the isostructural thermally decomposing Co-ZIF-zni. Electron density analysis shows that the Zn-N bonds are more ionic than the Co-N bonds, which have distinct covalent features.

Pair distribution function and Ga NMR study of aqueous Ga complexes.

The atomic structures, and thereby the coordination chemistry, of metal ions in aqueous solution represent a cornerstone of chemistry, since they provide first steps in rationalizing generally observed chemical information. However, accurate structural information about metal ion solution species is often surprisingly scarce. Here, the atomic structures of Ga ion complexes were determined directly in aqueous solutions across a wide range of pH, counter anions and concentrations by X-ray pair distribution function analysis and Ga NMR.

Direct observation of one-dimensional disordered diffusion channel in a chain-like thermoelectric with ultralow thermal conductivity.

Structural disorder, highly effective in reducing thermal conductivity, is important in technological applications such as thermal barrier coatings and thermoelectrics. In particular, interstitial, disordered, diffusive atoms are common in complex crystal structures with ultralow thermal conductivity, but are rarely found in simple crystalline solids. Combining single-crystal synchrotron X-ray diffraction, the maximum entropy method, diffuse scattering, and theoretical calculations, here we report the direct observation of one-dimensional disordered In chains in a simple chain-like thermoelectric InTe, which contains a significant In vacancy along with interstitial indium sites.

Exploring the structures, stability, and light absorption properties of three thiostannates synthesised at similar conditions.

We present the synthesis, crystal structures and optical properties of three thiostannates prepared by using 1-(2-aminoethyl)piperazine (AEPz) as structure directing agent. Two of the thiostannates are layered materials (AEPz-SnS-1 and AEPz:EtOH-SnS-1) consisting of [SnS] sheets with organic cations located in-between. The third compound is a molecular thiostannate (SnS(AEPzH)) composed of dimeric SnS and AEPzH.

On single-crystal total scattering data reduction and correction protocols for analysis in direct space.

Data reduction and correction steps and processed data reproducibility in the emerging single-crystal total-scattering-based technique of three-dimensional differential atomic pair distribution function (3D-ΔPDF) analysis are explored. All steps from sample measurement to data processing are outlined using a crystal of CuIrS as an example, studied in a setup equipped with a high-energy X-ray beam and a flat-panel area detector. Computational overhead as pertains to data sampling and the associated data-processing steps is also discussed.

First-order antiferromagnetic transitions of SrMnP and CaMnP single crystals containing corrugated-honeycomb Mn sublattices.

SrMnP and CaMnP are insulators that adopt the trigonal CaAlSi-type structure containing corrugated Mn honeycomb layers. Magnetic susceptibility and heat capacity versus temperature data reveal a weak first-order antiferromagnetic (AFM) transition at the Néel temperature [Formula: see text] K for SrMnP and a strong first-order AFM transition at [Formula: see text] K for CaMnP Both compounds exhibit isotropic and nearly -independent [Formula: see text], suggesting magnetic structures in which nearest-neighbor moments are aligned at [Formula: see text] to each other. The P NMR measurements confirm the strong first-order transition in CaMnP but show critical slowing down above [Formula: see text] for SrMnP, thus also evidencing second-order character.

Nickel-Mediated Alkoxycarbonylation for Complete Carbon Isotope Replacement.

Many commercial drugs, as well as upcoming pharmaceutically active compounds in the pipeline, display aliphatic carboxylic acids or derivatives thereof as key structural entities. Synthetic methods for rapidly accessing isotopologues of such compounds are highly relevant for undertaking critical pharmacological studies. In this paper, we disclose a direct synthetic route allowing for full carbon isotope replacement via a nickel-mediated alkoxycarbonylation.

Tuning of bandgaps and emission properties of light-emitting diode materials through homogeneous alloying in molecular crystals.

Alloy formation is ubiquitous in inorganic materials science, and it strongly depends on the similarity between the alloyed atoms. Since molecules have widely different shapes, sizes and bonding properties, it is highly challenging to make alloyed molecular crystals. Here we report the generation of homogenous molecular alloys of organic light emitting diode materials that leads to tuning in their bandgaps and fluorescence emission.

Stability and Thermoelectric Properties of ZnSb with TiO Nanoparticle Inclusions.

β-ZnSb is a cheap nontoxic high-performance thermoelectric material, which unfortunately suffers from stability issues because of zinc migration in thermal and electrical gradients. Here, the thermoelectric properties and thermal stability of β-ZnSb mixed with varying sizes and weight percentages of TiO nanoparticles are investigated. Furthermore, the stability of pressed β-ZnSb-TiO nanocomposite pellets is investigated by measuring high-energy synchrotron powder X-ray diffraction (PXRD) data during operating conditions using the Aarhus thermoelectric setup (ATOS).

Unravelling the complex formation mechanism of HfO nanocrystals using in situ pair distribution function analysis.

Hafnia, HfO, which is a wide band gap semiconducting oxide, is much less studied than the chemically similar zirconia (ZrO). Here, we study the formation of hafnia nanocrystals from hafnium tetrachloride in methanol under solvothermal conditions (248 bar, 225-450 °C) using complementary in situ powder X-ray diffraction (PXRD) and Pair Distribution Function (PDF) analysis. The main structural motif of the precursor solution (HfCl dissolved in methanol) is a Hf oxide trimer with very similar local structure to that of m-HfO.

A mechanism for ageing in a deeply supercooled molecular glass.

Measurements of the decay of electric fields, formed spontaneously within vapour-deposited films of cis-methyl formate, provide the first direct assessment of the energy barrier to secondary relaxation in a molecular glass. At temperatures far below the glass transition temperature, the mechanism of relaxation is shown to be through hindered molecular rotation. Magnetically-polarised neutron scattering experiments exclude diffusion, which is demonstrated to take place only close to the glass transition temperature.

Structural evolution in thermoelectric zinc antimonide thin films studied by X-ray scattering techniques.

Zinc antimonides have been widely studied owing to their outstanding thermoelectric properties. Unlike in the bulk state, where various structurally unknown phases have been identified through their specific physical properties, a number of intermediate phases in the thin-film state remain largely unexplored. Here, X-ray diffraction and X-ray total scattering are combined with measurement of electrical resistivity to monitor the crystallization process of as-deposited amorphous Zn-Sb films during post-deposition annealing.

Bandgap Tuning in Molecular Alloy Crystals Formed by Weak Chalcogen Interactions.

We demonstrate systematic tuning in the optical bandgaps of molecular crystals achieved by the generation of molecular alloys/solid solutions of a series of diphenyl dichalcogenides-characterized by weak chalcogen bonding interactions involving S, Se, and Te atoms. Despite the variety in chalcogen bonding interactions found in this series of dichalcogenide crystals, they show isostructural interaction topologies, enabling the formation of solid solutions. The alloy crystals exhibit Vegard's law-like trends of variation in their unit cell dimensions and a nonlinear trend for the variation in optical bandgaps with respect to their compositions.

High coercivity SmCo synthesized with assistance of colloidal SiO.

SmCo is one of the most promising candidates for achieving a hard magnet with a high coercivity. Usually, composition, morphology, and size determine the coercivity of a magnet, however, it is challenging to synthesize phase pure SmCo with optimal size and high coercivity. In this paper, we report on the successful synthesis of phase pure SmCo with spherical/prolate spheroids shape.

Improved Thermoelectric Properties of N-Type MgSb through Cation-Site Doping with Gd or Ho.

The success of n-type doping has attracted strong research interest for exploring effective n-type dopants for MgSb thermoelectrics. Herein, we experimentally study Gd and Ho as n-type dopants for MgSb thermoelectrics. The synthesis, structural characterization, and thermoelectric properties of Gd-doped, Ho-doped, (Gd, Te)-codoped, and (Ho, Te)-codoped MgSb samples are reported.

Tailoring the stoichiometry of CN nanosheets under electron beam irradiation.

Two-dimensional polymeric graphitic carbon nitride (g-C3N4) is a low-cost material with versatile properties that can be enhanced by the introduction of dopant atoms and by changing the degree of polymerization/stoichiometry, which offers significant benefits for numerous applications. Herein, we investigate the stability of g-C3N4 under electron beam irradiation inside a transmission electron microscope operating at different electron acceleration voltages. Our findings indicate that the degradation of g-C3N4 occurs with N species preferentially removed over C species.

Phase control for indium oxide nanoparticles.

The indium oxides, c-In2O3, h-In2O3, InOOH and In(OH)3, constitute an important class of wide band gap semiconductors. Synthesis of any indium oxide phase involves manoeuvring in a complex matrix of process parameters, and some phases are only obtained through controlled phase transformations. Considering the widespread use of indium oxide semiconductors it is restrictive that no coherent picture exists of the formation mechanisms of individual phases and phase transformations between them.

Probing Efficient N-Type Lanthanide Dopants for MgSb Thermoelectrics.

The recent discovery of n-type MgSb thermoelectrics has ignited intensive research activities on searching for potential n-type dopants for this material. Using first-principles defect calculations, here, a systematic computational screening of potential efficient n-type lanthanide dopants is conducted for MgSb. In addition to La, Ce, Pr, and Tm, it is found that high electron concentration (≳10 cm at the growth temperature of 900 K) can be achieved by doping on the Mg sites with Nd, Gd, Ho, and Lu, which are generally more efficient than other lanthanide dopants and the anion-site dopant Te.

Facile synthesis of brookite TiO nanoparticles.

Brookite is the most difficult TiO2 polymorph to obtain in phase pure form. Here we report on a facile synthesis method for phase-pure brookite nanoparticles using a broad range of titanium precursors. General availability of phase pure brookite opens up multiple research activities to explore both fundamental properties as well as applications.

Selective Catalytic Reduction of NO Using Phase-Pure Anatase, Rutile, and Brookite TiO Nanocrystals.

We demonstrate a facile selective synthesis of phase-pure anatase, rutile, and brookite nanocrystal polymorphs of titania (TiO) using a benign hydrothermal treatment of an industrial grade TiOSO precursor. Acetic acid (CHCOOH) is used for the synthesis of anatase, glycolic acid (HOCHCOOH) is used for rutile, and both glycolic acid and ammonium hydroxide (NHOH) are used for obtaining brookite. The detailed morphologies of the as-synthesized materials are determined from a combination of powder X-ray diffraction, transmission electron microscopy, and Raman spectroscopy.