The structure of dicalcium potassium heptahydrogen tetrakis(phosphate) dihydrate, Ca2KH7(PO4)4.2H2O, by X-ray and neutron diffraction

1984 ◽  
Vol 40 (9) ◽  
pp. 1499-1502
Author(s):  
E. Prince ◽  
S. Takagi ◽  
M. Mathew ◽  
W. E. Brown
Author(s):  
M. D. Vaudin ◽  
J. P. Cline

The study of preferred crystallographic orientation (texture) in ceramics is assuming greater importance as their anisotropic crystal properties are being used to advantage in an increasing number of applications. The quantification of texture by a reliable and rapid method is required. Analysis of backscattered electron Kikuchi patterns (BEKPs) can be used to provide the crystallographic orientation of as many grains as time and resources allow. The technique is relatively slow, particularly for noncubic materials, but the data are more accurate than any comparable technique when a sufficient number of grains are analyzed. Thus, BEKP is well-suited as a verification method for data obtained in faster ways, such as x-ray or neutron diffraction. We have compared texture data obtained using BEKP, x-ray diffraction and neutron diffraction. Alumina specimens displaying differing levels of axisymmetric (0001) texture normal to the specimen surface were investigated.BEKP patterns were obtained from about a hundred grains selected at random in each specimen.


2021 ◽  
Vol 60 (8) ◽  
pp. 6016-6026
Author(s):  
Aydar Rakhmatullin ◽  
Maxim S. Molokeev ◽  
Graham King ◽  
Ilya B. Polovov ◽  
Konstantin V. Maksimtsev ◽  
...  

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mily Kundu ◽  
Santanu Pakhira ◽  
Renu Choudhary ◽  
Durga Paudyal ◽  
N. Lakshminarasimhan ◽  
...  

AbstractTernary intermetallic compound $${\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}$$ Pr 2 Co 0.86 Si 2.88 has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ($$\mu$$ μ SR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below $$\sim$$ ∼ 4 K. Neutron diffraction measurement further reveals that the magnetic ordering is antiferromagnetic in nature with an weak ordered moment. The high temperature magnetic phase has been attributed to glassy in nature consisting of ferromagnetic clusters of itinerant (3d) Co moments as evident by the development of internal field in zero-field $$\mu$$ μ SR below 50 K. The density-functional theory (DFT) calculations suggest that the low temperature magnetic transition is associated with antiferromagnetic coupling between Pr 4f and Co 3d spins. Pr moments show spin fluctuation along with unconventional orbital moment quenching due to crystal field. The evolution of the symmetry and the crystalline electric field environment of Pr-ions are also studied and compared theoretically between the elemental Pr and when it is coupled with other elements such as Co. The localized moment of Pr 4f and itinerant moment of Co 3d compete with each other below $$\sim$$ ∼ 20 K resulting in an unusual temperature dependence of magnetic coercivity in the system.


2010 ◽  
Vol 43 (5) ◽  
pp. 1113-1120 ◽  
Author(s):  
Esko Oksanen ◽  
François Dauvergne ◽  
Adrian Goldman ◽  
Monika Budayova-Spano

H atoms play a central role in enzymatic mechanisms, but H-atom positions cannot generally be determined by X-ray crystallography. Neutron crystallography, on the other hand, can be used to determine H-atom positions but it is experimentally very challenging. Yeast inorganic pyrophosphatase (PPase) is an essential enzyme that has been studied extensively by X-ray crystallography, yet the details of the catalytic mechanism remain incompletely understood. The temperature instability of PPase crystals has in the past prevented the collection of a neutron diffraction data set. This paper reports how the crystal growth has been optimized in temperature-controlled conditions. To stabilize the crystals during neutron data collection a Peltier cooling device that minimizes the temperature gradient along the capillary has been developed. This device allowed the collection of a full neutron diffraction data set.


2001 ◽  
Vol 56 (6-7) ◽  
pp. 478-488
Author(s):  
Uwe Hoppe ◽  
Rainer Kranold ◽  
Emil Gattef ◽  
Jörg Neuefeind ◽  
David A. Keen

Abstract The short-range order of vitreous V20 5 and of three (Zn0)Jt(V20 5)1_x glasses with x = 0.2, 0.4, and 0.5 is studied by X-ray and neutron diffraction experiments where the change of the contrast allows to resolve the V -0 and Z n -0 correlations. The V -0 and the Z n -0 first-neighbor peaks are approximat­ ed by several Gaussian functions. In case of vitreous V20 5 two obvious V -0 distances exist which are related with V 0 4 and V 0 5 units. With ZnO additions the V -O coordination number decreases from 4.4 in vitreous V20 5 to 4.0 in the metavanadate glass where the strongest decrease of the fraction of V 0 5 units is found for glasses of * < 0.2. Dominantly, the V 0 5 groups are linked with the neighboring units by comers. The Z n-0 coordination numbers of the modified glasses are about five with closest dis­ tances of = 0.200 nm.


2013 ◽  
Vol 58 (4) ◽  
pp. 575-585 ◽  
Author(s):  
N. B. Bolotina ◽  
A. I. Kalyukanov ◽  
T. S. Chernaya ◽  
I. A. Verin ◽  
I. I. Buchinskaya ◽  
...  

1994 ◽  
Vol 376 ◽  
Author(s):  
M. Vrána ◽  
P. Klimanek ◽  
T. Kschidock ◽  
P. Lukáš ◽  
P. Mikula

ABSTRACTInvestigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.


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