In situ surface analysis of palladium-platinum alloys in methane oxidation conditions

Palladium and palladium-platinum foils were analysed using temperature-programmed near-ambient pressure x-ray photoelectron spectroscopy (TP-NAP-XPS) under methane oxidation conditions. Oxidation of palladium is inhibited by the presence of water, and in oxygen-poor environments. Pt addition further inhibits oxidation of palladium across all reaction conditions, preserving metallic palladium to higher temperatures. Bimetallic foils underwent significant restructuring under reaction conditions, with platinum preferentially migrating to the bulk under select conditions

Jahn-Teller driven electronic instability in thermoelectric tetrahedrite

Tetrahedrite, Cu12Sb4S13, is an abundant mineral with excellent thermoelectric properties owing to its low thermal conductivity. The electronic and structural origin of the intriguing physical properties of tetrahedrite, including its metal-to-semiconductor transition, remains largely unknown. This work presents the first determination of the low-temperature structure of tetrahedrite that accounts for its unique properties. Contrary to prior conjectures, our results show that the trigonal-planar copper cations remain in planar coordination below the metal-to-semiconductor transition. The atomic displacement parameters of the trigonal-planar copper cations, which have been linked to low thermal conductivity, increase by 200% above the metal-to-semiconductor transition. The phase transition is consequence of the orbital degeneracy of the highest occupied 3d cluster orbitals of the copper clusters found inside the sodalite cages in the cubic phase. This study reveals that a Jahn-Teller electronic instability leads to the formation of “molecular-like” Cu57+ clusters and suppresses copper rattling vibrations due to the strengthening of direct copper-copper interactions. Our first-principles calculations demonstrate that the structural phase transition opens a small band gap in the electronic density of states and eliminates the unstable phonon modes. The present results provide insights on the interplay between phonon transport, electronic properties and crystal structure in mixed-valence compounds

Solvation structure of propane/propene in [C4mim][NTf2] ionic liquid - II

Data collected on the SANDALS instrument at the ISIS facility, RB1920307. Results from previous beamtime (RB1620078) demonstrated that proposed differences in olefin/alkane solvation in the ionic liquid (from MD simulation) can be observed experimentally from EPSR analysis of the neutron scattering data, however the resolution of the analysis was severely limited by the restricted number of independent data sets collected and the H/D-isotopic substitutions used. The aim of this continuation is to obtain further data comparing the solvation environments of propane and propene in [C4mim][NTf2] using (i) equivalent mole fractions of dissolved hydrocarbon rather than constant gas pressure, (ii) use deuteriated propane and propene to increase the number of available isotopic contrasts, and (iii) use selective H/D-substitution between the IL imidazolium ring and butyl-chain to enhance the resolution of analysis

Research data supporting the publication "Synthesis and characterisation of the new oxyanion doped “0201–1201” type layered oxide, Sr4.5Fe2(S/Cr)0.5O9±δ"

conductivity.zip : Conductivity data for Sr4.5Fe2(S/Cr)0.5O9±δ Mossbauer.zip: Mossbauer data for Sr4.5Fe2(S/Cr)0.5O9±δ ND.zip Neutron powder diffraction data for Sr4.5Fe2(S/Cr)0.5O9±δ XANES.zip Chromium XANES data for Sr4.5Fe2Cr0.5O9±δ XRD.zip X-ray powder diffraction data for Sr4.5Fe2(S/Cr)0.5O9±

Research data supporting the publication "Synthesis and characterisation of the new oxyanion doped “0201–1201” type layered oxide, Sr4.5Fe2(S/Cr)0.5O9±δ"

conductivity.zip : Conductivity data for Sr4.5Fe2(S/Cr)0.5O9±δ Mossbauer.zip: Mossbauer data for Sr4.5Fe2(S/Cr)0.5O9±δ ND.zip Neutron powder diffraction data for Sr4.5Fe2(S/Cr)0.5O9±δ XANES.zip Chromium XANES data for Sr4.5Fe2Cr0.5O9±δ XRD.zip X-ray powder diffraction data for Sr4.5Fe2(S/Cr)0.5O9±

Polarization Analysis for Seeded FELs in a Crossed-Planar Undulator

The crossed-planar undulator is a promising scheme for full polarization control in x-ray FELs. For SASE FELs, it has been shown a maximum degree of circular polarization of about 80% is achievable at fundamental wavelength just before saturation. In this paper, we study the effectiveness of a crossed undulator for a seeded x-ray FEL. The degree of circular polarization for both the fundamental and the harmonic radiation are considered. Simulations with realistic beam distributions show that a degree of circular polarization of over 90% and 80% is obtainable at the fundamental and 2nd harmonic frequencies, respectively

Data for "Sulfamerazine: Understanding the influence of slip-planes in the polymorphic phase transformation through X-ray crystallographic studies and ab initio lattice dynamics"

Raw data to accompany the paper "Sulfamerazine: Understanding the influence of slip-planes in the polymorphic phase transformation through X-ray crystallographic studies and ab initio lattice dynamics"

Solvent-solute interations in PET recycling systems

Neutron scattering datasets (SANDALS) from RB1820154 Abstract: Glycolysis of polyethylterephthalate (PET) catalysed by ionic liquid solvents could offer a metal-free low cost approach to chemical recycling of waste PET. This work will investigate the solvent-substrate interactions the products from glycolysis of PET and ionic liquid solvents/catalysts which will lead to insight into the development of new ionic liquid technologies to explore recycling post-consumer plastics. Principal Investigator: Professor John Holbrey Experimenter: Mr Gareth Nelson Local Contact: Dr Sabrina Gaertner DOI: 10.5286/ISIS.E.RB1820154 ISIS Experiment Number: RB1820154 Publisher: STFC ISIS Neutron and Muon Source Data format: RAW/Nexu