scholarly journals Advanced calculations of X-ray spectroscopies with FEFF10 and Corvus

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
J. J. Kas ◽  
F. D. Vila ◽  
C. D. Pemmaraju ◽  
T. S. Tan ◽  
J. J. Rehr
Keyword(s):  
Real Space ◽  
Vibrational Properties ◽  
Many Body ◽  
Edge Structure ◽  
Pump Probe ◽  
X Ray ◽  
X Ray Scattering ◽  
Function Code ◽  
Electron Energy Loss ◽  
X Ray Absorption

The real-space Green's function code FEFF has been extensively developed and used for calculations of X-ray and related spectra, including X-ray absorption (XAS), X-ray emission (XES), inelastic X-ray scattering, and electron energy-loss spectra. The code is particularly useful for the analysis and interpretation of the XAS fine-structure (EXAFS) and the near-edge structure (XANES) in materials throughout the periodic table. Nevertheless, many applications, such as non-equilibrium systems, and the analysis of ultra-fast pump–probe experiments, require extensions of the code including finite-temperature and auxiliary calculations of structure and vibrational properties. To enable these extensions, we have developed in tandem a new version FEFF10 and new FEFF-based workflows for the Corvus workflow manager, which allow users to easily augment the capabilities of FEFF10 via auxiliary codes. This coupling facilitates simplified input and automated calculations of spectra based on advanced theoretical techniques. The approach is illustrated with examples of high-temperature behavior, vibrational properties, many-body excitations in XAS, super-heavy materials, and fits of calculated spectra to experiment.

scholarly journals Progress and challenges in the theory and interpretation of x-ray spectra

2014 ◽  
Vol 70 (a1) ◽  
pp. C1516-C1516
Author(s):  
John Rehr ◽  
Joshua Kas
Keyword(s):  
Fine Structure ◽  
Real Space ◽  
Bragg Diffraction ◽  
Strongly Correlated ◽  
Complex Materials ◽  
Many Body ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
New Generation

There has been dramatic progress in recent years both in calculations and the interpretation of various x-ray spectra, ranging from extended x-ray absorption fine structure (EXAFS) and diffraction-anomalous fine structure (DAFS) to near-edge structure (XANES) and inelastic x-ray scattering (IXS). Using synchrotron radiation x- ray sources, these spectroscopies have become powerful probes of complex materials ranging from catalysts and minerals to bio-structures and aqueous systems. Together with advances in analysis techniques, these methods permit an interpretation of spectra in terms of structural, electronic, magnetic and vibrational properties. We summarize these advances first with a heuristic description of the real-space approach used in the electronic structure and spectroscopy codes developed by our group [1]. Our approach is based on real-space multiple-scattering Green's function techniques, rather than wave-functions. This simplifies calculations of excited states and x-ray spectra, particularly the inclusion of key many-body effects and relativistic corrections. The approach is illustrated with applications to various x-ray spectra of complex materials. For example, DAFS takes advantage of the fine structure in the intensity of Bragg diffraction peaks near an absorption edge, and provides unique information that combines EXAFS and XRD experiment. We also discuss some recent theoretical developments leading to a new generation of codes including FEFF9 [2] and extensions for treating strongly correlated systems.

scholarly journals Real-space multiple-scattering calculation and interpretation of x-ray-absorption near-edge structure

1998 ◽  
Vol 58 (12) ◽  
pp. 7565-7576 ◽  
Author(s):  
A. L. Ankudinov ◽  
B. Ravel ◽  
J. J. Rehr ◽  
S. D. Conradson
Keyword(s):  
Multiple Scattering ◽  
Real Space ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Small-angle X-ray scattering and X-ray absorption near-edge structure study of iron-doped siloxane-polyoxyethylene nanocomposites

2003 ◽  
Vol 36 (3) ◽  
pp. 405-409 ◽  
Author(s):  
L.A Chiavacci ◽  
K Dahmouche ◽  
C.V Santilli ◽  
V de Zea Bermudez ◽  
L.D Carlos ◽  
...  
Keyword(s):  
Small Angle ◽  
Structure Study ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Iron Doped ◽  
X Ray Absorption ◽  
Ray Scattering

The use of XANES and ELNES for the Characterisation of Stabilised Zirconia

2001 ◽  
Vol 699 ◽  
Author(s):  
David W. McComb ◽  
Sergei Ostanin ◽  
Dimitris Vlachos ◽  
Alan J. Craven ◽  
Michael W. Finnis ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Full Potential ◽  
Data Simulation ◽  
Edge Structure ◽  
Materials Analysis ◽  
X Ray ◽  
Lmto Method ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Atomic Coordinates

AbstractThe electron energy-loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) at the oxygen K-edge has been investigated in a range of yttria-stabilised zirconia (YSZ) materials. Analysis of near-edge structure reveals that both the crystallographic phase and the metal fraction of yttrium present can be determined directly from the oxygen K-edge data. Simulation of the ELNES/XANES was achieved using a pseudopotential based method to obtain the relaxed atomic coordinates combined with full-potential LMTO method to calculate the electronic structure.

scholarly journals Core-hole effects on theoretical electron-energy-loss near-edge structure and near-edge x-ray absorption fine structure of MgO

2000 ◽  
Vol 61 (3) ◽  
pp. 2180-2187 ◽  
Author(s):  
Teruyasu Mizoguchi ◽  
Isao Tanaka ◽  
Masato Yoshiya ◽  
Fumiyasu Oba ◽  
Kazuyoshi Ogasawara ◽  
...  
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Core Hole ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Electron Energy Loss ◽  
X Ray Absorption

Energy-filtered imaging of constituent phases in polymer blends

1996 ◽  
Vol 54 ◽  
pp. 164-165
Author(s):  
E. L. Hall ◽  
G. A. Hutchins
Keyword(s):  
Spatial Resolution ◽  
Structural Damage ◽  
Chemical Nature ◽  
Phase Distribution ◽  
Core Loss ◽  
Edge Structure ◽  
X Ray ◽  
Engineering Plastics ◽  
Electron Energy Loss ◽  
X Ray Absorption

Many engineering plastics consist of complex blends of chemically-distinct constituent polymers and other additives. These components are added in order to achieve desired performance in a variety of properties, including mechanical behavior, processability, color, fire retardency, and others. The distribution of the components, as well as the nature of the interfaces between constituents, are critically important to the performance of the engineering plastic. For many years, TEM has been the key tool in determining phase distribution. However, TEM studies are often limited by the need to stain the various constituents in order to achieve contrast, and also by the inability of TEM methods to unambiguously identify the chemical nature of the various constituents in the image. In the recent past, both electron energy loss spectroscopy (EELS) in the TEM and x-ray absorption near-edge spectroscopy (XANES) using synchrotron sources have demonstrated the ability to differentiate constituents based on characteristic carbon core loss edge structure. The EELS technique has the benefit of high spatial resolution, while the XANES method causes much less structural damage and mass loss. The advent of imaging energy filters has led to a third method for phase delineation for chemically distinct components, which combines the spatial resolution of EELS with the imaging capabilities of XANES.

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