Pressure effects on the EXAFS Debye–Waller factor of iron

2020 ◽  
Vol 27 (5) ◽  
pp. 1372-1375
Author(s):  
Ho Khac Hieu ◽  
Nguyen Ba Duc ◽  
Nguyen Van Hung ◽  
Pham Thi Minh Hanh ◽  
Tran Thi Hai
Keyword(s):  
Relative Displacement ◽  
Debye Model ◽  
Waller Factor ◽  
Pressure Effects ◽  
Displacement Curve ◽  
Mean Square ◽  
Debye Waller Factor ◽  
Debye Frequency ◽  
X Ray Absorption ◽  
Analytical Expressions

The pressure effects on atomic mean-square relative displacement characterizing the extended X-ray absorption fine structure (EXAFS) Debye–Waller factor of iron metal have been investigated based on the Debye model. The analytical expressions of the Debye frequency and EXAFS Debye–Waller factor have been derived as functions of crystal volume compressibility. Based on the well established equation-of-state including the contributions of the anharmonic and electronic thermal pressures, numerical calculations have been performed for iron up to a pressure of 220 GPa and compared with experimental data when possible. These results show that the Debye frequency increases rapidly with compression, and beyond 150 GPa it behaves as a linear function of pressure. Meanwhile the mean-square relative displacement curve drops robustly with pressure, especially at pressures smaller than 100 GPa. This phenomenon causes the enhancement of EXAFS signals at high pressure. Reversely, the increasing of temperature will reduce the amplitude of EXAFS spectra.

ISOTOPIC EFFECT IN DEBYE–WALLER FACTOR OF CRYSTALLINE GERMANIUM

2013 ◽  
Vol 27 (26) ◽  
pp. 1350191
Author(s):  
HO KHAC HIEU ◽  
VU VAN HUNG
Keyword(s):  
Lattice Dynamics ◽  
Mass Difference ◽  
Relative Displacement ◽  
Waller Factor ◽  
Isotopic Effect ◽  
Mean Square ◽  
X Ray ◽  
Debye Waller Factor ◽  
X Ray Absorption ◽  
Crystalline Germanium

The statistical moment method has been used to study the effect of isotopic mass difference on extended X-ray absorption fine structure (EXAFS) Debye–Waller factor of crystalline germanium. The effects on the parallel mean-square relative displacement and the atomic mean square displacements have been considered. This research also exposed that isotopic effect is noticeable where the correlated atomic motion is concerned. Numerical calculations have been performed for two isotopes 70 Ge and 76 Ge in range of temperature from 0 K to 600 K. Our results are compared with available experimental EXAFS data [J. Purans et al., Phys. Rev. Lett.100 (2008) 055901] as well as with lattice dynamics calculations [A. Sanson, Solid State Sci.12 (2010) 1988] and the good agreements are found.

scholarly journals A METHOD FOR CALCULATION OF MORSE POTENTIAL FOR FCC, BCC, HCP CRYSTALS APPLIED TO DEBYE-WALLER FACTOR AND EQUATION OF STATE

2007 ◽  
Vol 14 (1) ◽  
pp. 7 ◽  
Author(s):  
NGUYEN VAN HUNG
Keyword(s):  
Fine Structure ◽  
Equation Of State ◽  
Lattice Constant ◽  
Morse Potential ◽  
Waller Factor ◽  
X Ray ◽  
Debye Waller Factor ◽  
X Ray Absorption ◽  
Analytical Expressions ◽  
Potential Parameters

Analytical expressions for the Morse potential parameters for fcc, bcc and hcp crystals have been developed. They contain the energy of sublimation, the compressibility and the lattice constant. Numerical results for Cu (fcc), W (bcc) and Zn (hcp) agree well with the measured values. Debye-Waller factors in X-ray absorption fine structure (XAFS) and equation of state computed using the obtained Morse potential parameters agree well with the experimental results.

scholarly journals EXAFS Debye-Waller Factors of B2-FeAl Alloys

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
Nguyen Thi Hong ◽  
Nguyen Ba Duc ◽  
Ho Khac Hieu
Keyword(s):  
Debye Model ◽  
Al Alloys ◽  
Temperature Dependent ◽  
X Ray ◽  
Debye Frequency ◽  
X Ray Absorption ◽  
Analytical Expressions ◽  
Theoretical Results ◽  
B2 Structure ◽  
Good Agreement

This work develops the anharmonic correlated Debye model to study the temperature-dependent extended X-ray absorption fine structure (EXAFS) Debye-Waller factors (DWFs) of B2-FeAl alloys. We derived the analytical expressions of the EXAFS DWF and Debye frequency as functions of temperature. Numerical calculations were performed for Fe1-yAly alloys with various Al concentration (y = 0.35, 0.40, 0.45 and 0.50) in which Fe-Al alloys still maintained B2 structure. The good agreement between our theoretical results with previous data verifies our developed theory. Our calculations show that DWFs of Fe1-yAly alloys increase robustly when temperature and/or Al concentration in Fe1-yAly alloys increase. The increasing of DWF will cause the reduction of the amplitude of EXAFS.

scholarly journals A METHOD FOR CALCULATION OF MORSE POTENTIAL FOR FCC, BCC, HCP CRYSTALS APPLIED TO DEBYE-WALLER FACTOR AND EQUATION OF STATE

2007 ◽  
Vol 14 (1) ◽  
pp. 7
Author(s):  
NGUYEN VAN HUNG
Keyword(s):  
Fine Structure ◽  
Equation Of State ◽  
Lattice Constant ◽  
Morse Potential ◽  
Waller Factor ◽  
X Ray ◽  
Debye Waller Factor ◽  
X Ray Absorption ◽  
Analytical Expressions ◽  
Potential Parameters

Analytical expressions for the Morse potential parameters for fcc, bcc and hcp crystals have been developed. They contain the energy of sublimation, the compressibility and the lattice constant. Numerical results for Cu (fcc), W (bcc) and Zn (hcp) agree well with the measured values. Debye-Waller factors in X-ray absorption fine structure (XAFS) and equation of state computed using the obtained Morse potential parameters agree well with the experimental results.

Study on Effects of Heavy Ion Irradiation on CeO2 by Using Synchrotron Radiation X-Ray Absorption Spectroscopy -as a Simulation Study for Radiation Damage in High-Burnup Light Water Reactor Fuels-

2007 ◽  
Vol 1043 ◽  
Author(s):  
Hirotaka Ohno ◽  
Daiju Matsumura ◽  
Yasuo Nishihata ◽  
Jun'ichiro Mizuki ◽  
Norito Ishikawa ◽  
...  
Keyword(s):  
Thin Films ◽  
Synchrotron Radiation ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
Waller Factor ◽  
X Ray ◽  
Debye Waller Factor ◽  
Atomic Distance ◽  
Exafs Measurement ◽  
X Ray Absorption

AbstractCeO2 thin films were irradiated with 200MeV Xe ions. Effects of the irradiation were studied by using Extended X-ray Absorption Fine Structure (EXAFS) measurement at SPring8 synchrotron radiation facility. EXAFS spectra for the irradiated thin films near the Ce K-edge show that the coordination number for oxygen atoms around Ce atom decreases and that the Ce-O Debye-Waller factor increases by the irradiation. The atomic distance between oxygen atom and Ce atom does not vary within the accuracy of EXAFS measurement. The effect of high density electronic excitation on the structure of CeO2 is discussed.

scholarly journals Thermodynamic Properties and Anharmonic Effects in XAFS Based on Anharmonic Correlated Debye Model Debye–Waller Factors

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Nguyen Ba Duc ◽  
Nguyen Van Hung ◽  
Ha Dang Khoa ◽  
Dinh Quoc Vuong ◽  
Tong Sy Tien
Keyword(s):  
Thermodynamic Properties ◽  
Present Theory ◽  
Debye Model ◽  
Near Neighbor ◽  
Atomic Interaction ◽  
Single Pair ◽  
Many Body ◽  
Anharmonic Effects ◽  
X Ray Absorption ◽  
Analytical Expressions

Thermodynamic properties and anharmonic effects in X-ray absorption fine structure (XAFS) have been studied based on the anharmonic correlated Debye model Debye–Waller factors presented in terms of cumulant expansion. The derived analytical expressions of three first XAFS cumulants involve more information on phonon-phonon interactions taken from integration over the first Brillouin zone. Many-body effects are taken into account in the present one-dimensional model based on the first shell near neighbor contributions to the vibrations between absorber and backscatterer atoms. Morse potential is assumed to describe single-pair atomic interaction included in the derived anharmonic interatomic effective potential. The present theory can be applied to any crystal structure including complex systems. Numerical results for Cu and Ni are found to be in good agreement with experiment and with those of the other theories.

scholarly journals Effect of the non-ideal axial ratio c/a on anharmonic EXAFS oscillation of h.c.p. crystals

2021 ◽  
Vol 28 (5) ◽  
Author(s):  
Tong Sy Tien
Keyword(s):  
Axial Ratio ◽  
Debye Model ◽  
Waller Factor ◽  
Calculation Model ◽  
Near Neighbor ◽  
Perturbation Approach ◽  
Many Body ◽  
Hexagonal Close Packed ◽  
Debye Waller Factor ◽  
The Many

The temperature and wavenumber dependence of the extended X-ray absorption fine-structure (EXAFS) oscillation of hexagonal close-packed (h.c.p.) crystals have been calculated and analyzed under the effect of the non-ideal axial ratio c/a. The anharmonic EXAFS oscillation is presented in terms of the Debye–Waller factor using the cumulant expansion approach up to the fourth order. An effective calculation model is expanded and developed from the many-body perturbation approach and correlated Debye model using the anharmonic effective potential. This potential, depending on the non-ideal axial ratio c/a, is obtained from the first-shell near-neighbor contribution approach. A suitable analysis procedure is performed by evaluating the influence of EXAFS cumulants on the phase shift and amplitude reduction of the anharmonic EXAFS oscillation. The numerical results for crystalline zinc are found to be in good agreement with those obtained from experiments and other theoretical methods at various temperatures. The obtained results show that the present theoretical model is essential and effective in improving the accuracy for analyzing the experimental data of anharmonic EXAFS signals of h.c.p. crystals with a non-ideal axial ratio c/a.

Correlation effects studied based on Debye–Waller factors. Application to fcc crystals

2019 ◽  
Vol 33 (20) ◽  
pp. 1950237
Author(s):  
Nguyen Van Hung ◽  
Dinh Quoc Vuong
Keyword(s):  
Mean Square Displacement ◽  
Relative Displacement ◽  
Debye Model ◽  
Atomic Interaction ◽  
Single Pair ◽  
Mean Square ◽  
Correlation Effects ◽  
Many Body ◽  
The Difference ◽  
Experimental Values

Correlation effects described by the displacement–displacement correlation function [Formula: see text] have been studied based on Debye–Waller factors presented by the mean square displacement (MSD) [Formula: see text] and mean square relative displacement (MSRD) [Formula: see text] in X-ray Absorption Fine Structure. Analytical expressions have been derived for [Formula: see text] based on the anharmonic correlated Debye model (ACDM) and for [Formula: see text] based on anharmonic Debye model (ADM) or uncorrelated Debye model. Many-body effects have been taken into account in the present one-dimensional model by a simple measure based on the anharmonic effective potentials that include interactions of absorber and backscatterer atoms with their nearest neighbors. Morse potential is used for describing single-pair atomic interaction. The reasons for the difference between MSRD and MSD have been discussed in detail. The theory is applied to fcc crystals and can be generalized to any crystal structure. Numerical results for Cu are found to be in good agreement with the experimental values and with those taken from the measured Morse parameters, as well as with the values of [Formula: see text] calculated using the other theories.

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