An efficient technique for calculating x-ray Raman scattering spectra at the K edge in the framework of a single-particle theory is presented. It is based on a recursive method to compute the dynamic structure factor as a continued fraction without requiring the explicit calculation of high-lying unoccupied electronic states. Multipole transitions are calculated to provide a full account of the q-dependence of K edges recorded in a series of lithium-bearing reference compounds, namely LiBO 2 , Li 2 CO 3 , Li 2 O, and LiF. The good agreement obtained between experimental and theoretical spectra validates our approach and provides a solid foundation for analyzing K edges beyond the dipole approximation.
Iron oxide-based catalysts can selectively covert CO 2 to added-value CO in parallel with on-purpose ethylene production via ethane dehydrogenation (CO 2 -EDH). The 5Fe/10NiMgZr catalyst, calcined at 700 °C for 5 h, reached 90% selectivity, at a single-pass C 2 H 6 conversion of ∼23.3%, during CO 2 -EDH at 650 °C. X-ray characterization techniques (XRD, XPS, XAS, and XRS), along with structural modeling were used to elucidate the nature of highly selective active sites toward C−H bond scission. Under reaction conditions, Fe atoms are incorporated into the support lattice, as it was exemplified by XRS at Mg L 2,3 -and O K-edges. The dynamic structural modifications, occurring during CO 2 -EDH, highlighted the pivotal role of the support, reaching an ethylene yield of 21%. Mg coordination altered from octahedral to tetrahedral. The latter was accompanied by an electronic modification, which had a strong impact on the catalyst acidity, based on Fourier transform infrared spectroscopy combined with in situ adsorption of pyridine, resulting in an unpresented ethylene selectivity for Fe oxide-based catalysts.
Atomistic details about the hydration of Na+- and Cl−-ions in aqueous solutions are studied by a combination of X-ray spectroscopy and spectrum calculation based on molecular dynamics simulations.
A new ternary phase with a composition Al 1+x V 2 Sn 2-x (x=0.19) has been found during the investigation of the Al-V-Sn ternary system. Single crystal X-ray diffraction measurements reveal that this ternary phase crystallizes with an orthorhombic structure with a = 5.5931(1) Å, b = 18.8017(5) Å and c = 6.7005(2) Å (Space group Cmce). This compound is thus isostructural to the GaV 2 Sn 2 structure type, showing a layered structure composed of vanadium clusters band formed with pentagonal faces intercalated by tin atoms layer. High resolution transmission electron microscopy measurements confirm the orthorhombic structure. Regarding lattice perfection, no dislocation could be identified within the probed Al 1.19 V 2 Sn 1.81 single crystal lamella.Ab initio calculations reveal a reduction of the density of states at the Fermi level, which could be attributed to both a Hume Rothery effect combined with strong spd hybridization.
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