1,721,035 research outputs found
Ionic liquids as solvents for rare-earth metals: a combined XAS and Molecular Dynamics study
Full text linkIn this work a detailed investigation of the structural organization of ILs, both monocationic and dicationic, and their water mixtures has been carried out by combining XAS spectroscopy and Classical MD simulations. The same joint XAS-MD approach has been also applied to the study of the solvation properties of Ln(III) salts dissolved in ILs. The original application of EXAFS and MD simulations paves the route for the systematic use of an integrated approach, with increased reliability, in the structural investigation of ILs. All together these issues are expected to be of great help in the systematic design of IL systems to meet the requirements of key applications
Exact thermal and structural damping of the multiple scattering contributions to the XANES
No full textThermal and structural damping of the multiple-scattering contributions to the x-ray-absorption coefficient
No full textEXAFS and XANES simulations of Fe/Co hexacyanoferrate spectra by GNXAS and MXAN
No full textIn the present paper Full Multiple Scattering (FMS) theory has been applied to analyse the cobalt hexacyanoferrate XANES spectra. The use of the MXAN program has permitted to calculate the edge spectra and to perform a fitting procedure with the experimental data, obtaining a set of structural parameters. A previously reported EXAFS analysis (which includes terms up to four-body MS calculations) was performed via the GNXAS package, by a Multiple Edge approach of both Fe/Co K-edges and Fe/Co/Ni K-edges, and using the same structural parameters for all edges. The XANES data of Fe and Co K-edges are independently analysed here. An excellent reproduction of the XANES spectra, and a good agreement with the previous EXAFS results is obtained. The CN bond length using EXAFS has been determined with a statistical error of few thousandths of Å, whereas structural parameter using MXAN are probed within a 0.01-0.03 Å accuracy
Nuovi sviluppi nell‘ analisi strutturalequantitativa di spettri XAS: applicazioni biologiche
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Combined XANES and EXFAS analysis of Co2+, Ni2+ and Zn2+ aqueous solutions
No full textA combined x-ray-absorption near edge structure (XANES) and extended x-ray-absorption fine-structure (EXAFS) quantitative analysis of Co2+, Ni2+, and Zn2+ in water solutions based on fitting procedures of both low- and high-energy ranges has been carried out. The hydrogen contribution has been accounted for in both analyses and the effect of its inclusion on the structural parameters has been highlighted. The structural results obtained from the XANES and EXAFS analyses are in good agreement, confirming the validity of the application of the multiple-scattering theory in the low-energy range of the x-ray-absorption spectra. A systematic shortening of the ion-water first shell distance of about 0.03 Å is obtained from the XANES analyses, as compared to the EXAFS one. The origin of this systematic effect has been deeply investigated and it has been found to be due to the low-energy behavior of the real part of the Hedin-Lundqvist potential used in the calculations
Hemeproteins: Recent Advances in Quantitative XANES Analysis
No full textRecently, we have shown that multiple scattering (MS) theory, via the MXAN package, is able to reproduce the experimental X-ray absorption near edge structure (XANES) data of biological samples, in particular hemeproteins, from the rising edge up to similar to 150-200 eV above the edge. In the present work, we illustrate how XANES can be used either as an independent tool to provide bond-lengths and bond-angles for a metalloprotein active site in solution, or in combination with X-ray Diffraction for structural determinations of ligand binding geometry of the same diffracting protein crystal, providing atomic precision even for crystallographic structures solved at > 1.2 angstrom resolution. At low temperature, XANES can be applied to provide the Fe-heme structure of trapped intermediate conformations; of fight triggered processes, and some aspects of the ligand binding dynamics. Very recently, XANES difference spectra have been analyzed to provide the Fe-heme structure of multiple intermediates of carbonmonoxy-myoglobin, obtained under different photolysis protocols in solution state
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