scholarly journals X-ray Absorption Fine Structure of bcc Crystals Studied Based on High-order Expanded Debye-Waller Factors

2017 ◽  
Vol 27 (1) ◽  
pp. 55
Author(s):  
Nguyen Van Hung ◽  
Trinh Thi Hue ◽  
Ha Dang Khoa ◽  
Tong Sy Tien
Keyword(s):  
Fine Structure ◽  
High Order ◽  
Atomic Interaction ◽  
Perturbation Approach ◽  
Single Pair ◽  
Many Body ◽  
X Ray ◽  
Absorption Fine ◽  
The Many ◽  
X Ray Absorption

In this work, X-ray absorption fine structure (XAFS) of bcc crystals and it Fourier transformmagnitude have been studied based on the anharmonic correlated Debye model high-order expandedDebye-Waller factors. The many-body effects are taken into account in the present one-dimensionalmodel based on the anharmonic effective potential that includes interactions of absorber andbackscatterer atoms with their first shell near neighbors, where Morse potential is assumed to describethe single-pair atomic interaction. Analytical expressions of four first temperature-dependent cumulantsof bcc crystals have been derived using the many-body perturbation approach. The obtained cumulantsare applied to calculating XAFS spectra and their Fourier transform magnitudes. Numerical results forFe are found to be in good agreement with experiment.

An extended X-ray absorption fine structure study of amorphous and crystalline germanium

1981 ◽  
Vol 59 (7) ◽  
pp. 876-882 ◽  
Author(s):  
E. D. Crozier ◽  
A. J. Seary
Keyword(s):  
Fine Structure ◽  
Random Network ◽  
Structural Disorder ◽  
Structure Study ◽  
Additional Contribution ◽  
Many Body ◽  
X Ray ◽  
Absorption Fine ◽  
Body Potential ◽  
X Ray Absorption

Extended X-ray absorption fine structure (EXAFS) results are presented for amorphous and crystalline Ge at temperatures ranging from 83 to 1085 K. Specific tests for the detection of asymmetry in the distribution of atoms are examined. In amorphous Ge the distribution of nearest neighbours is found to be Gaussian. In crystalline Ge at the highest temperatures studied a small asymmetry in the distribution of nearest atoms, attributed to anharmonicity in the effective two-body potential, must be included explicitly in the EXAFS analysis to determine changes in nearest neighbour distances to an accuracy of ± 0.01 Å. The temperature dependence of the disorder parameter σ12 in crystalline Ge is found to obey an Einstein model, contrary to earlier work. The structure of amorphous Ge is found to be consistent with a continuous random network of distorted tetrahedra in which the dynamic contribution to σ12(T) is given by the same force-constant law as in crystalline Ge. The static structural disorder provides an additional contribution to a σ12(T) which decreases as the crystalline temperature is approached. Many-body contributions to the reduction of the amplitude of the EXAFS interference function in amorphous and crystalline Ge are also determined empirically.

scholarly journals Anharmonic correlated Debye model Debye-Waller factors of metallic Copper compared to experiment and to other theories

2017 ◽  
Vol 33 (3) ◽  
Author(s):  
Nguyen Van Hung
Keyword(s):  
Metallic Copper ◽  
Pair Potential ◽  
Debye Model ◽  
Near Neighbor ◽  
Atomic Interaction ◽  
Perturbation Approach ◽  
Single Pair ◽  
Many Body ◽  
The Many ◽  
Analytical Expressions

Debye-Waller factors (DWFs) of metallic Cu (fcc crystal) in X-ray absorption fine structure (XAFS) presented in terms of cumulant expansion have been studied using the anharmonic correlated Debye model (ACDM). This ACDM is derived using the many-body perturbation approach and the anharmonic effective potential that includes the first shell near neighbor contributions to the vibration between absorber and backscatterer atoms. Analytical expressions of three first XAFS cumulants of Cu have been derived involving more information of phonon-phonon interactions taken from integration over the first Brillouin zone. Morse potential is assumed to describe the single-pair atomic interaction. Numerical results for Cu using the present ACDM show their good agreement with experiment and with those of other theories, as well as their advantage compared to those calculated using the single-pair potential.

Many-body effects on extended x-ray absorption fine structure amplitudes

1980 ◽  
Vol 21 (12) ◽  
pp. 5521-5539 ◽  
Author(s):  
E. A. Stern ◽  
B. A. Bunker ◽  
S. M. Heald
Keyword(s):  
Fine Structure ◽  
Many Body ◽  
X Ray ◽  
Absorption Fine ◽  
Many Body Effects ◽  
X Ray Absorption

High-order multiple-scattering calculations of x-ray-absorption fine structure

1992 ◽  
Vol 69 (23) ◽  
pp. 3397-3400 ◽  
Author(s):  
J. J. Rehr ◽  
R. C. Albers ◽  
S. I. Zabinsky
Keyword(s):  
Fine Structure ◽  
Multiple Scattering ◽  
High Order ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

scholarly journals Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua

2018 ◽  
Vol 120 (9) ◽  
Author(s):  
Dimitar Popmintchev ◽  
Benjamin R. Galloway ◽  
Ming-Chang Chen ◽  
Franklin Dollar ◽  
Christopher A. Mancuso ◽  
...  
Keyword(s):  
Fine Structure ◽  
High Order ◽  
X Ray ◽  
Absorption Fine ◽  
High Order Harmonic ◽  
X Ray Absorption

scholarly journals Thermodynamic parameters depend on temperature with the influence of doping ratio of the crystal structure metals in extended X-Ray absorption fine structure

2021 ◽  
Vol 4 (10) ◽  
pp. 5-10
Author(s):  
Ba Duc Nguyen ◽  
Quang Tho Vu ◽  
Phi Hiep Trinh ◽  
Quynh Lam Nguyen Thi
Keyword(s):  
Crystal Structure ◽  
Fine Structure ◽  
Thermodynamic Parameters ◽  
Effective Potential ◽  
Single Pair ◽  
Face Centered Cubic ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption ◽  
Doping Ratio

The effects of the doping ratio and temperature on the cumulants andthermodynamic parameters of crystal structure metals and their alloys wasinvestigated using the anharmonic correlated Einstein model, in extended X-ray absorption fine structure (EXAFS) spectra. We derived analytical expressions for the EXAFS cumulants, correlated Einstein frequency, Einstein temperature, and effective spring constant. We have considered parameters of the effective Morsepotential and the Debye-Waller factor depend on temperature and the effects of the doping ratio of face-centered-cubic (fcc) crystals of copper (Cu-Cu), silver (Ag-Ag), and hexagonal-close-packed (hcp) crystal of zinc (Zn-Zn), and their alloys of Cu-Ag and Cu-Zn. The derived anharmonic effective potential includes the contributions of all the nearest neighbors of the absorbing and scattering atoms. This accounts for three-dimensional interactions and the parameters of theMorse potential, to describe single-pair atomic interactions. The numericalresults of the EXAFS cumulants, thermodynamic parameters, and anharmonic effective potential agree reasonably with experiments and other theories.

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