Short-Range Order and Static Displacements in Polycrystalline Ni-13.1at. %W Alloy

2018 ◽  
Vol 271 ◽  
pp. 98-105
Author(s):  
Lhkamsuren Enkhtor ◽  
Ragchaa Galbadrakh ◽  
Valentin Silonov

A methodology accounting for the contributions of static displacements of atoms to X-ray diffuse scattering by binary solid solutions with a face-centered cubic lattice was proposed. By microscopic accounting of static displacements of the atoms on the particular shell, we identified short- range order parameters on the first eight shells of Ni-13.1at. %W alloy from the intensity of X-ray diffuse scattering. The Fourier transform of static displacement of the atoms on every considered shell was calculated with the De Launay model using expressions of elements of dynamical matrix and Fourier transforms of quasi elastic forces, which are calculated by the pseudopotential method.

2021 ◽  
Vol 323 ◽  
pp. 159-165
Author(s):  
Lkhamsuren Enkhtur ◽  
Valentin Silonov ◽  
Tsedendorj Gantulga ◽  
Galbadrakh Ragchaa ◽  
Tsenddavaa Amartaivan ◽  
...  

In this paper, we are proposing a novel method to estimate static displacements of atoms caused by size effects in fcc substitutional binary polycrystalline solid solutions. Fourier transforms of static displacements of the atoms on every considered shell were calculated using the equations that include dynamical matrix and Fourier transform of interatomic forces. Short-range order parameters on the first seven shells of Ni-14 at. % Ir alloy have been identified from X-ray diffuse scattering intensity by accounting microscopic static displacements of atoms on a particular shell. Pairwise interatomic potentials on the considered shells and critical temperature of disorder-order phase transition were calculated using values of short-range order parameters.


2019 ◽  
Vol 288 ◽  
pp. 65-70 ◽  
Author(s):  
Lhkamsuren Enkhtor ◽  
Valentin Silonov

An expression for calculating the critical temperature of order-disorder transition in face-centered cubic alloys is developed with accounting of pairwise interatomic potential in the first eleven shells. Obtained expression was applied for the estimation of critical temperatures at Cu3Au, CuAu, and CuAu3alloys in comparison with experimental data from phase diagram of Cu-Au system. Magnitudes of the pairwise interatomic potential in considered alloys was computed using values of the short-range order parameters which were experimentally obtained from X-ray diffuse scattering intensity. In this computation, the Krivoglaz-Clapp-Moss approximation and Cowley equations were applied.


2003 ◽  
Vol 59 (3) ◽  
pp. 384-392 ◽  
Author(s):  
J. Krawczyk ◽  
A. Pietraszko ◽  
R. Kubiak ◽  
K. Łukaszewicz

Crystals of uranium iodine phthalocyanine present an example of a disordered commensurate modulated structure of the intergrowth type. The short-range order of both uranium ions and iodine chains [I_3^-] n has been analysed by Reverse Monte Carlo (RMC) simulation of X-ray diffuse scattering. The diffraction pattern of uranium iodine phthalocyanine contains diffuse superstructure reflections. In the routine crystal structure analysis diffuse superstructure reflections may be either omitted or measured and classified along with other Bragg reflections. The crystal structure of uranium iodine phthalocyanine is an example of such ambiguity. The crystal structures of two specimens of [U1−x Pc2]I2−y with slightly different composition have been published in the literature with different space groups and unit cells. We have shown that the structure of both specimens differs only in the degree of short-range order and is isostructural with [YbPc2]I2. We have also shown that while the omission of diffuse reflections results in the average crystal structure, the treatment of these reflections as normal Bragg reflections is incorrect and produces the structure averaged over a limited small range.


1995 ◽  
Vol 77 (1) ◽  
pp. 34-40 ◽  
Author(s):  
X. B. Kan ◽  
H. Renevier ◽  
J. Quintana ◽  
J. L. Peng ◽  
J. B. Cohen

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