Temperature- and energy-dependent phase shifts of resonant multiple-beam X-ray diffraction in germanium crystals

2015 ◽  
Vol 71 (4) ◽  
pp. 460-466 ◽  
Author(s):  
Po-Yu Liao ◽  
Wen-Chung Liu ◽  
Chih-Hao Cheng ◽  
Yi-Hua Chiu ◽  
Ying-Yu Kung ◽  
...  

This paper reports temperature- and energy-dependent phase shifts of resonant multiple-beam X-ray diffraction in germanium crystals, involving forbidden (002) and weak (222) reflections. Phase determination based on multiple-beam diffraction is employed to estimate phase shifts from (002)-based \{(002)(375)(37\overline{3})\} four-beam cases and (222)-based \{ (222)(\overline{5}3\overline{3})\} three-beam cases in the vicinity of the GeKedge for temperatures from 20 K up to 300 K. The forbidden/weak reflections enhance the sensitivity of measuring phases at resonance. At room temperature, the resonance triplet phases reach a maximum of 8° for the four-beam cases and −19° for the three-beam cases. It is found that the peak intensities and triplet phases obtained from the (002) four-beam diffraction are related to thermal motion induced anisotropy and anomalous dispersion, while the (222) three-beam diffraction depends on the aspherical covalent electron distribution and anomalous dispersion. However, the electron–phonon interaction usually affects the forbidden reflections with increasing temperatures and seems to have less effect on the resonance triplet phase shifts measured from the (002) four-beam diffraction. The resonance triplet phase shifts of the (222) three-beam diffractionversustemperature are also small.

2007 ◽  
Vol 22 (8) ◽  
pp. 2185-2188 ◽  
Author(s):  
B. Xu ◽  
W.F. Zhang ◽  
X.Y. Liu ◽  
J. Yin ◽  
Z.G. Liu

The photocatalyst BaZn1/3Nb2/3O3 with ABO3 perovskite structure has been synthesized by using a solid-state reaction process. It was characterized by x-ray diffraction and photoluminescence spectroscopy. The luminescence band centers around 285 nm and shows a large Stokes shift compared with the excitation spectrum, indicating a strong electron–phonon interaction in the photocatalyst BaZn1/3Nb2/3O3. The electronic structure of BaZn1/3Nb2/3O3 was calculated by using the pseudopotential method of the density function theory. It shows that the conduction band should be mainly composed of the Nb 4d states, and the valence band should be mainly composed of the O 2p state. The densities of the O 2p states and the Zn 4s states at the bottom of the conduction band are very low. The Zn 4s states show an expanded structure, which was proposed to be helpful for the migration of the photoexcited carriers, thus favoring the photocatalytic activity of BaZn1/3Nb2/3O3.


2008 ◽  
Vol 22 (32) ◽  
pp. 3195-3205 ◽  
Author(s):  
M. LI ◽  
S. L. HUANG ◽  
Z. M. LV ◽  
J. L. ZHANG ◽  
H. Y. WU ◽  
...  

Powder X-ray diffraction, Raman scattering and infrared spectra at different doping (x = 0 ~ 0.5) on polycrystalline Pr 1-x Sr 1+x CoO 4 were performed. With increasing x, the shift of Raman scattering spectra is due to the enhancement of electron–phonon interaction along the c-axis. The contrary variation of infrared in wavenumber comes from the weakening electron–phonon interactions in the ab plane. There is a dramatic variation in resistivity as x increases, which is also caused by increasing carrier concentration and is related to the band shift. For Pr 1-x Sr 1+x CoO 4, both A1g bands shift to low frequency and reach a minimum when x = 0.3 and the resistivity of Pr 0.7 Sr 1.3 CoO 4 is the smallest at room temperature.


2001 ◽  
Vol 63 (9) ◽  
Author(s):  
John P. Sutter ◽  
E. Ercan Alp ◽  
Michael Y. Hu ◽  
Peter L. Lee ◽  
Harald Sinn ◽  
...  

2020 ◽  
Vol 117 (9) ◽  
pp. 092102 ◽  
Author(s):  
Yongzhao Yao ◽  
Yoshiyuki Tsusaka ◽  
Yukari Ishikawa ◽  
Yoshihiro Sugawara ◽  
Yu Fujita ◽  
...  

2017 ◽  
Vol 46 (3) ◽  
pp. 733-738
Author(s):  
Kun Lin ◽  
Na Wang ◽  
Li You ◽  
Qiang Li ◽  
Kenichi Kato ◽  
...  

We give strong evidence that Pb2+/Bi3+ tend to be disordered in perovskite structures, which is attributed to similar electron configurations and comparable coordinate environments.


2010 ◽  
Vol 43 (4) ◽  
pp. 926-928 ◽  
Author(s):  
X. R. Huang

LauePtis a robust and extremely easy-to-use Windows application for accurately simulating, indexing and analyzing white-beam X-ray diffraction Laue patterns of any crystals under arbitrary diffraction geometry. This program has a user-friendly graphic interface and can be conveniently used by nonspecialists with little X-ray diffraction or crystallography knowledge. Its wide range of applications include (1) determination of single-crystal orientation with the Laue method, (2) white-beam topography, (3) white-beam microdiffraction, (4) X-ray studies of twinning, domains and heterostructures, (5) verification or determination of crystal structures from white-beam diffraction, and (6) teaching of X-ray crystallography.


2021 ◽  
Vol 54 (3) ◽  
Author(s):  
Zheng Tang ◽  
Lirong Zheng ◽  
Shengqi Chu ◽  
Pengfei An ◽  
Xianrong Huang ◽  
...  

On the basis of rigorous dynamical-theory calculations, a complete X-ray polarization-switch effect of silicon crystals at the exact multiple-beam diffraction condition is demonstrated. The underlying physical mechanism of this unique phenomenon can be revealed using a simple multiple-wave propagation and interference model. The constructive and destructive interference of the multiple detoured-diffraction beams along the direction of the primary diffracted beam directly leads to the complete polarization switch. This phenomenon can be realized using both synchrotron and laboratory X-ray sources at many discrete wavelengths, and used to design a novel crystal-based polarizer to achieve a 90° polarization rotation.


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