Full multiple scattering

FULL MULTIPLE SCATTERING CALCULATIONS ON HgTe UNDER HIGH PRESSURE AT THE MERCURY L3 X-RAY ABSORPTION EDGE... 

Fig. 22. Best fit between experimental results and computed EXAFS employing the full multiple scattering method. The model is depicted in the bottom right figure [Reprinted from Thomas and Sankar (104) with permission. Copyright (2001) American Chemical Society].

Figure 5 shows DOS from self-consistent field, full multiple scattering calculations as implemented in the FEFF8 code33 on the supported Ptio cluster illustrated. The support is mimicked by the 3 water molecules as shown the O atoms represent the O atoms in the support, and the H atoms effectively terminate the cluster and represent the Si or A1 atoms such as that in a zeolite. The DOS are shown from calculations with and without a core-hole on the 3 different site symmetries (surface, edge, and center). 

Real space full multiple scattering calculations... 

The FEFF8 code31 was used to perform self-consistent full multiple scattering calculations. FEFF8 implements self-consistent field potentials for the determination of the Fermi-level and the charge transfer. Full multiple scattering (FMS) calculations are used to calculate the X-ray Absorption Near-Edge Structure (XANES) and the local density of states. 

By comparing the total cross section obtained from a full multiple scattering calculation shown in the upper part of Fig. 10 with the EXAFS term we observe that the two spectra are very similar above 3 Rydberg. This effect is determined by the destructive interference between the n 3 contributions. The negative interference between n = 3 and n = 4 contributions is clearly shown in Fig. 10. This destructive interference between higher order contributions is characteristic of octahedral coordination and disappears for distortion of the octahedra. 

Here we discuss the effect of bond length on XANES spectra. It is well known that EXAFS oscillations are determined by the interatomic distances and coordination numbers. Also a full multiple scattering resonance in the XANES range is strongly affected by interatomic distance. 

Fronzoni G, Stener M, Decleva P (1999) Theoretical study of the excited and continuum states in the NEXAFS regions of Cl2. Phys Chem Chem Phys 1 1405-1414 Fujikawa T, Oizumi H, Oyanagi H, Tokumoto M, Kuroda H (1986) Short-range order full multiple scattering approach to die polarized -edge XANES of Br-doped in Trans-polyacetylene. J Phys Soc. Japan 55 4090-4102... 

Weiher N, WiUnef EA, FiguUa-Kroschel C et al (2003) Extended X-ray absorption fine-structure (EXAFS) of a complex oxide structure a full multiple scattering analysis of the Au Ls-edge EXAFS of AU2O3. Solid State Commun 125 317-322... 

We now want to describe the ampHtude change caused by a distortion of the surface, possibly including displacements of several atoms. Of course, we first need the wave field of the reference structure as this is to be perturbed. Imagine that we have a state e(koii)> representing the plane wave with parallel momentum kon and energy e impinging on the surface. Assume further that we know the full operator G+, which by action on e(koii)) creates the wave field due to full multiple scattering at the reference stracture so that outside the crystal, the set of diffracted waves... 

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