Neutron Instruments for Research in Coordination Chemistry.

Neutron diffraction and spectroscopy offer unique insight into structures and properties of solids and molecular materials. All neutron instruments located at the various neutron sources are distinct, even if their designs are based on similar principles, and thus, they are usually less familiar to the community than commercial X-ray diffractometers and optical spectrometers. Major neutron instruments in the USA, which are open to scientists around the world, and examples of their use in coordination chemistry research are presented here, along with a list of similar instruments at main neutron facilities in other countries.

Inelastic Neutron Scattering Study of Phonon Density of States of Iodine Oxides and First-Principles Calculations.

Iodine oxides IO ( = 4, 5, 6) crystallize into atypical structures that fall between molecular- and framework-base types and exhibit high reactivity in an ambient environment, a property highly desired in the so-called "agent defeat materials". Inelastic neutron scattering experiments were performed to determine the phonon density of states of the newly synthesized IO and IO samples. First-principles calculations were carried out for IO, IO, and IO to predict their thermodynamic properties and phonon density of states.

Polyhedral Distortions and Unusual Magnetic Order in Spinel FeMnO.

Spinel compounds ABX consist of both tetrahedral (AX) and octahedral (BX) environments with the former forming a diamond lattice and the latter a geometrically frustrated pyrochlore lattice. Exploring the fascinating physical properties and their correlations with structural features is critical in understanding these materials. FeMnO has been reported to exhibit one structural transition and two successive magnetic transitions.

Structure of the Solid-State Electrolyte LiPAlS: Lithium-Ion Transport Properties in Crystalline vs Glassy Phases.

The search for new solid electrolyte materials and an understanding of fast-ion conductivity are crucial for the development of safe and high-power all-solid-state battery technology. Herein, we present the synthesis, structure, and properties of a crystalline lithium-ion conductor, LiAlPS (i.e.

LaZrO Nanoparticle-Mediated Synthesis of Porous Al-Doped LiLaZrO Garnet.

In this work, we modified the reaction pathway to quickly (minutes) incorporate lithium and stabilize the ionic conducting garnet phase by decoupling the formation of a La-Zr-O network from the addition of lithium. To do this, we synthesized LaZrO (LZO) nanoparticles to which LiNO was added. This method is a departure from typical solid-state synthesis methods that require high-energy milling to promote mixing and intimate particle-particle contact and from sol-gel syntheses as a unique porous microstructure is obtained.

Layered-rocksalt intergrown cathode for high-capacity zero-strain battery operation.

The dependence on lithium-ion batteries leads to a pressing demand for advanced cathode materials. We demonstrate a new concept of layered-rocksalt intergrown structure that harnesses the combined figures of merit from each phase, including high capacity of layered and rocksalt phases, good kinetics of layered oxide and structural advantage of rocksalt. Based on this concept, lithium nickel ruthenium oxide of a main layered structure (R[Formula: see text]m) with intergrown rocksalt (Fm[Formula: see text]m) is developed, which delivers a high capacity with good rate performance.

Defect-Accommodating Intermediates Yield Selective Low-Temperature Synthesis of YMnO Polymorphs.

In the synthesis of complex oxides, solid-state metathesis provides low-temperature reactions where product selectivity can be achieved through simple changes in precursor composition. The influence of precursor structure, however, is less understood in solid-state synthesis. Here we present the ternary metathesis reaction (LiMnO + YOCl → YMnO + LiCl) to target two yttrium manganese oxide products, hexagonal and orthorhombic YMnO, when starting from three different LiMnO precursors.

Synthesis, Crystal Structure, and Cooperative 3-5 Magnetism in Rock Salt Type LiNiOsO and LiNiOsO.

Two new transition metal oxides with the nominal chemical compositions of LiNiOsO and LiNiOsO were successfully synthesized. Both compounds crystallize in an ordered rock salt structure type in the monoclinic 2/ space group. The crystal structures were determined using both synchrotron X-ray and time-of-flight neutron, powder diffraction data.

Radical Dimerization in a Plastic Organic Crystal Leads to Structural and Magnetic Bistability with Wide Thermal Hysteresis.

The nitroxyl radical 1-methyl-2-azaadamantane -oxyl (Me-AZADO) exhibits magnetic bistability arising from a radical/dimer interconversion. The transition from the rotationally disordered paramagnetic plastic crystal, Me-AZADO, to the ordered diamagnetic crystalline phase, (Me-AZADO), has been conclusively demonstrated by crystal structure determination from high-resolution powder diffraction data and by solid-state NMR spectroscopy. The phase change is characterized by a wide thermal hysteresis with high sensitivity to even small applied pressures.

POWGEN: rebuild of a third-generation powder diffractometer at the Spallation Neutron Source.

The neutron powder diffractometer POWGEN at the Spallation Neutron Source has recently (2017-2018) undergone an upgrade which resulted in an increased detector complement along with a full overhaul of the structural design of the instrument. The current instrument has a solid angular coverage of 1.2 steradians and maintains the original third-generation concept, providing a single-histogram data set over a wide -spacing range and high resolution to access large unit cells, detailed structural refinements and / measurements.

Incommensurate Magnetism Near Quantum Criticality in CeNiAsO.

We report the discovery of incommensurate magnetism near quantum criticality in CeNiAsO through neutron scattering and zero field muon spin rotation. For T View Article and Find Full Text PDF

In Situ Neutron Diffraction Studies of the Metal Flux Growth of Ba/Yb/Mg/Si Intermetallics.

The Ba/Yb/Mg/Si intermetallic system is extremely complex, with four competing structurally related compounds forming from reactions of barium, ytterbium, and silicon in magnesium-rich Mg/Al flux. In addition to the previously reported BaYbMgSi, BaYbMgSi, and BaYbMgSi, a new compound has been found. BaYbMgSi crystallizes in the P6̅ space group, with the ZrNiP structure type.

Boosting Solid-State Diffusivity and Conductivity in Lithium Superionic Argyrodites by Halide Substitution.

Developing high-performance all-solid-state batteries is contingent on finding solid electrolyte materials with high ionic conductivity and ductility. Here we report new halide-rich solid solution phases in the argyrodite Li PS Cl family, Li PS Cl , and combine electrochemical impedance spectroscopy, neutron diffraction, and Li NMR MAS and PFG spectroscopy to show that increasing the Cl /S ratio has a systematic, and remarkable impact on Li-ion diffusivity in the lattice. The phase at the limit of the solid solution regime, Li PS Cl , exhibits a cold-pressed conductivity of 9.

Identification of the strong Brønsted acid site in a metal-organic framework solid acid catalyst.

It remains difficult to understand the surface of solid acid catalysts at the molecular level, despite their importance for industrial catalytic applications. A sulfated zirconium-based metal-organic framework, MOF-808-SO, was previously shown to be a strong solid Brønsted acid material. In this report, we probe the origin of its acidity through an array of spectroscopic, crystallographic and computational characterization techniques.

AGES: Automated Gas Environment System for neutron powder diffraction.

High fluxes available at modern neutron and synchrotron sources have opened up a wide variety of and studies of real processes using scattering techniques. This has allowed the user community to follow chemistry in the beam, which often requires high temperatures, gas flow, etc. In this paper, we describe an integrated gas handling system for the general-purpose powder diffraction beamline Powgen at the Spallation Neutron Source.

Structural-Distortion-Driven Magnetic Transformation from Ferro- to Ferrimagnetic Iron Chains in B -based Nb FeIr B.

We report on a structural distortion of kinetically stable B -based ferromagnetic Nb FeIr B that induces an unprecedented transformation of a ferromagnetic Fe chain into two ferrimagnetic Fe chains through superstructure formation. Density functional theory calculations showed that the ferromagnetic Fe-Fe intrachain interactions found in the undistorted structure become ferrimagnetic in the distorted superstructure, mainly because the two independent iron atoms building each chain interact antiferromagnetically and carry different magnetic moments. High-temperature SQUID magnetometry confirmed ferrimagnetic ordering at 525 K with a high and negative Weiss constant of -972 K indicating the presence of strong antiferromagnetic interactions, as predicted.

Insights into B-Site Ordering in Double Perovskite-Type BaCaNbO (0 ≤ x ≤ 0.45): Combined Synchrotron and Neutron Diffraction and Electrical Transport Analyses.

Perovskite-type metal oxides are being used in a wide range of technologies, including fuel cells, batteries, electrolyzers, dielectric capacitors, and sensors. One of their remarkable structural properties is cationic ordering in A or B sites, which affects electrical transport properties under different gaseous atmospheres, and chemical stability under CO and humid conditions. For example, a simple-perovskite-type Y-doped BaCeO forms BaCO and ((Ce,Y)O) under CO at elevated temperature, while B-site-ordered double-perovskite-type BaCaNbO remains chemically stable under the same conditions.

Unraveling the Role of Structural Order in the Transformation of Electrical Conductivity in CaFeCoO, CaSrFeCoO, and SrFeCoO.

The ability to control the electrical conductivity of solid-state oxides using structural parameters has been demonstrated. A correlation has been established between the electrical conductivity and structural order in a series of oxygen-deficient perovskites using X-ray and neutron diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and electrical conductivity studies at a wide temperature range, 25-800 °C. The crystal structure of CaSrFeCoO has been determined, and its stark contrast to CaFeCoO and SrFeCoO has been demonstrated.

Transformation of Structure, Electrical Conductivity, and Magnetism in AA'FeO, A = Sr, Ca and A' = Sr.

The ability to control electrical properties and magnetism by varying the crystal structure using the effect of the A-site cation in oxygen-deficient perovskites has been studied in AA'FeO, where A = Sr, Ca and A' = Sr. The structure of SrFeO, synthesized at 1250 °C in air, contains dimeric units of FeO square pyramids separated by FeO octahedra. Here we show that this ordering scheme can be transformed by changing the A-site cations from Sr to Ca.

Rechargeable Aluminum-Ion Batteries Based on an Open-Tunnel Framework.

Rechargeable batteries based on an abundant metal such as aluminum with a three-electron transfer per atom are promising for large-scale electrochemical energy storage. Aluminum can be handled in air, thus offering superior safety, easy fabrication, and low cost. However, the development of Al-ion batteries has been challenging due to the difficulties in identifying suitable cathode materials.

Postsynthetic Functionalization of Mg-MOF-74 with Tetraethylenepentamine: Structural Characterization and Enhanced CO Adsorption.

Postsynthetic functionalization of magnesium 2,5-dihydroxyterephthalate (Mg-MOF-74) with tetraethylenepentamine (TEPA) resulted in improved CO adsorption performance under dry and humid conditions. XPS, elemental analysis, and neutron powder diffraction studies indicated that TEPA was incorporated throughout the MOF particle, although it coordinated preferentially with the unsaturated metal sites located in the immediate proximity to the surface. Neutron and X-ray powder diffraction analyses showed that the MOF structure was preserved after amine incorporation, with slight changes in the lattice parameters.

Structural, Electronic, and Optical Properties of KSnO with an Offset Hollandite Structure.

We present the compound KSnO, a Sn-containing oxide with a unique structure type among oxides. The compound is orthorhombic and reminiscent of an offset hollandite, where open channels hold a row of four K per channel per cell. UV-visible spectroscopy indicates a wide band gap semiconductor, which is confirmed by first-principles electronic-structure calculations of band structures, densities of states, and optical properties.

Structure and Thermochemistry of Perrhenate Sodalite and Mixed Guest Perrhenate/Pertechnetate Sodalite.

Treatment and immobilization of technetium-99 (Tc) contained in reprocessed nuclear waste and present in contaminated subsurface systems represents a major environmental challenge. One potential approach to managing this highly mobile and long-lived radionuclide is immobilization into micro- and meso-porous crystalline solids, specifically sodalite. We synthesized and characterized the structure of perrhenate sodalite, Na[AlSiO](ReO), and the structure of a mixed guest perrhenate/pertechnetate sodalite, Na[AlSiO](ReO)(TcO).

Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates.

We report a novel production method for uranium oxyfluoride [(UO2)7F14(H2O)7]·4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl fluoride, UO2F2, through the gas phase at ambient temperatures followed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7]·4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous structure), and a water molecule binds as an equatorial ligand to the uranyl ion.