Local crystal lattice curvature measurements for bent‐crystal spectrometers

1990 ◽  
Vol 61 (1) ◽  
pp. 121-123 ◽  
Author(s):  
U. Schumacher ◽  
R. Nolte
1982 ◽  
Vol 26 ◽  
pp. 259-267
Author(s):  
Charles Goldsmith ◽  
George A. Walker

AbstractThe powder diffraction x-ray technique commonly used to measure strain in polycrystalline materials requires a knowledge of the elastic constants in order to convert the strain into a stress value. For many materials, these constants are not always known. Another technique to measure strain is the x-ray lattice curvature (substrate bending) method which requires no knowledge of the film elastic constants. The strain is measured in the substrate and requires only the elastic constants of the substrate to convert the measured strain into stress. Using a combination of the powder diffraction technique and a double crystal lattice curvature technique, the elastic constants of TaSi2 and WSi2 have been determined for various crystallographic directions.


2017 ◽  
Vol 743 ◽  
pp. 13-18
Author(s):  
Anna Drozdova ◽  
Alexander Nyavro ◽  
Lyudmila Kveglis

The article deals with the investigation of structure and magnetic properties of plastically deformed Ni51Ti49 alloy. The magnetic hysteresis loops confirm the presence of ferromagnetic properties in the alloy. The transmission electron microscopy (TEM) detects the appearance of lenticular crystals with bending contours which indicate the large distortion of the crystal lattice. The crystal lattice curvature occurs due to the large atom displacement. As a result, icosahedral clusters with the Frank-Kasper (FK) structure can be formed. The spin-polarized density of electron states and the magnetic moments for both non-deformed (near-spherical structure) and deformed (elongated by 5% along the Z-axis) Ni7Ti5 (FK-12), Ni8Ti5 (FK-13), and Ni10Ti6 (FK-16) clusters are calculated for the explanation of possibility of magnetization appearance in Ni51Ti49 alloy. The calculations show the increase in the magnetic moments for the deformed clusters. The calculated spectra demonstrate the high density of electron states near the Fermi level which is a characteristic feature of ferromagnetic alloys.


2009 ◽  
Vol 17 (13) ◽  
pp. 11172 ◽  
Author(s):  
Giovanni Mana ◽  
Enrico Massa ◽  
Luca Ferroglio
Keyword(s):  
X Ray ◽  

Author(s):  
W. Z. Chang ◽  
D. B. Wittry

Since Du Mond and Kirkpatrick first discussed the principle of a bent crystal spectrograph in 1930, curved single crystals have been widely utilized as spectrometric monochromators as well as diffractors for focusing x rays diverging from a point. Curved crystal diffraction theory predicts that the diffraction parameters - the rocking curve width w, and the peak reflection coefficient r of curved crystals will certainly deviate from those of their flat form. Due to a lack of curved crystal parameter data in current literature and the need for optimizing the choice of diffraction geometry and crystal materials for various applications, we have continued the investigation of our technique presented at the last conference. In the present abstract, we describe a more rigorous and quantitative procedure for measuring the parameters of curved crystals.The diffraction image of a singly bent crystal under study can be obtained by using the Johann geometry with an x-ray point source.


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