Multiple Scattering Calculation of Absorption Spectrum and Diffraction Calculation: Application to Nanometer Scale Copper Metallic Particle

Abstract

Jusqu'à présent, seule la partie EXAFS (Extended x-ray absorption fine structure) du spectre d'absorption X i.e. celle comprise entre 40.eV et 1000.eV après seuil était simulée. L'avènement de codes de calculs performants tenant compte des processus de diffusion multiple du photoelectron nous permet désormais une simulation fiable du seuil d'absorption (XANES : X-ray absorption near edge structure). Dans le domaine des agrégats métalliques nanométriques supportés, nous comparons les résultats obtenus avec deux codes de calculs FEFF6 écrit par J. RHER et CONTINUUM écrit par NATOLI et montrons la complémentarité existant entre la spectroscopie d'absorption X et la diffraction aux grands angles (WAXS : Wide Angle X-ray Scattering)

Comparison between X-ray Absorption Spectroscopy, Anomalous Wide Angle X-ray Scattering, Anomalous Small Angle X-ray Scattering, and Diffraction Anomalous Fine Structure Techniques Applied to Nanometer-Scale Metallic Clusters

“…A similar approach was made for a 55 copper atom cluster (Figure ). The major point that has to be made is that the presence of the features B and C of the copper foil K edge are already present. , Since the surface atoms have a non isotropic environment, features are present but with lower intensities than for the copper foil spectrum. Finally, regarding the structure A, as we have mentioned before for the L edge, this structure normally has to be band structure dependent.…”

Nanoscale bimetallic catalysts: are they really bimetallic?

“…7 In the case of nanosize metallic particles, synchrotron radiation has already proved its usefulness and has been discussed. 8,9 In the present paper we wish to give examples of how to elucidate the structure of nanoscale bimetallic particles using Ł Correspondence to: L. Guczi in situ X-ray adsorption near-edge spectroscopy (XANES). Reduction of the metal ions in the samples and the effect of subsequent air exposure are followed by the in situ technique.…”

Numerical Simulation of the Platinum LIII Edge White Line Relative to Nanometer Scale Clusters

“…For this kind of material, we try to define an experimental approach using the different techniques related to synchrotron radiation. In particular the necessity to use X-ray absorption spectroscopy as well as anomalous diffraction in order to obtain a fine structural description has already been underlined. − Moreover, using new codes liked FEFF based on the development of the scattering series − or CONTINUUM, it has been shown that the XANES of K absorption edge can be used to obtain information regarding the size of the metallic particle. , …”

“…[21][22][23][24][25][26][27] Moreover, using new codes liked FEFF based on the development of the scattering series [28][29][30] or CONTINUUM, 31 it has been shown that the XANES of K absorption edge can be used to obtain information regarding the size of the metallic particle. 32,33 Let us now consider the L III edge and more particularly the so-called "white line" to evaluate the effect of different parameter on this particular feature. We will focus here on nanometer scale platinum clusters with the FCC structure (O h symmetry), namely, cuboctahedra with 13 and 55 atoms.…”