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Extended X-ray absorption fine structure
About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.
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TL;DR: In this paper, it was shown that molybdate groups are not directly linked to the borosilicate network but rather located within alkali and alkaline-earth rich domains in the glass.
109 citations
TL;DR: Li et al. as mentioned in this paper investigated the mechanism responsible for the structural integrity shown by Li-rich layered oxides, which favors the formation of O22−-like species, with the aid of in situ extended X-ray absorption fine structure (EXAFS), in situ energy loss spectroscopy (EELS), and density functional theory (DFT) calculation.
Abstract: Lithium-rich layered oxides are considered as promising cathode materials for Li-ion batteries with high energy density due to their higher capacity as compared with the conventional LiMO2 (e.g., LiCoO2, LiNiO2, and LiNi1/3Co1/3Mn1/3O2) layered oxides. However, why lithium-rich layered oxides exhibit high capacities without undergoing a structural collapse for a certain number of cycles has attracted limited attention. Here, based on the model of Li2RuO3, it is uncovered that the mechanism responsible for the structural integrity shown by lithium-rich layered oxides is realized by the flexible local structure due to the presence of lithium atoms in the transition metal layer, which favors the formation of O22−-like species, with the aid of in situ extended X-ray absorption fine structure (EXAFS), in situ energy loss spectroscopy (EELS), and density functional theory (DFT) calculation. This finding will open new scope for the development of high-capacity layered electrodes.
109 citations
TL;DR: In this article, Germanium thin films were prepared by epitaxial vacuum evaporation onto CaF2 substrates and the absorption spectra of these films reveal, besides the fundamental absorption edge and its spin-orbit splitting, additional structure at higher energies.
Abstract: Thin films of several III–V and II–VI zinc‐blende‐type semiconductors were prepared by vacuum evaporation. Germanium thin films were prepared by epitaxial vacuum evaporation onto CaF2 substrates. The absorption spectra of these films reveal, besides the fundamental absorption edge and its spin‐orbit splitting, additional structure at higher energies. This structure has been interpreted along the lines followed in the interpretation of the reflection spectra of these materials. The agreement between the values for the various energy gaps derived from absorption and from reflection spectra is excellent.
108 citations
TL;DR: In this paper, a tentative structure model is proposed, in which islands of surface tungstate species are formed by branched chains of WO{sub 5} units.
Abstract: Tungsten oxide supported on titania is an important material for the selective catalytic reduction of nitrogen oxides NO{sub x}. A structure analysis by means of X-ray absorption spectroscopy (XANES and EXAFS) is reported for materials prepared by spreading of WO{sub 3} in physical mixtures with the support oxide as well as by impregnation from aqueous solution. A comparison is also made with alumina-supported materials. Analysis of the XANES region at the W L{sub 1} and W L{sub 3} edges indicated that tungsten is hexavalent and anchored to the surface as WO{sub 5} and WO{sub 4} units, the relative proportion of which increases with loading. When water is absorbed, pseudooctahedrally coordinated species are formed in both cases. The analysis of the EXAFS provides additional support for the existence of these structures, which contain oxo groups W{double bond}O and W-O-W bridges. A tentative structure model is proposed, in which islands of surface tungstate species are formed by branched chains of WO{sub 5} units. The chains are assumed to be terminated by WO{sub 4} units, the WO{sub 5}/WO{sub 4} ratio thus increasing with chain length or island size, which obviously increases with loading.
108 citations
TL;DR: In this article, hybrid molecular orbital/density functional theory (MO/DFT) calculations on molecular clusters were used to model infrared vibrational frequencies and interatomic distances obtained via extended X-ray absorption fine structure (EXAFS) spectroscopy.
Abstract: Summary Hybrid molecular orbital/density functional theory (MO/DFT) calculations on molecular clusters were used to model infrared (IR) vibrational frequencies and interatomic distances obtained via extended X-ray absorption fine structure (EXAFS) spectroscopy. Molecular clusters were found to provide good agreement with experimental observations for the oxyanions carbonate, phosphate, sulphate, arsenate and arsenite. The results show a consistent tendency to form bidentate bridging surface complexes at low pH, but the protonation and hydration states play a significant role in the results obtained from calculation as various protonation states of monodentate surface complexes are also predicted to be stable as pH increases (i.e. the number of H þ ions in the model are decreased). A method for estimating the Gibbs free energy of adsorption (DGads) is discussed to complement the comparisons of experimental and theoretical spectroscopic parameters. Calculated DGads values were consistent with the interpretations based on modelling observed spectra.
108 citations