scholarly journals Size-dependent phase diagrams of metallic alloys: A Monte Carlo simulation study on order–disorder transitions in Pt–Rh nanoparticles

2012 ◽  
Vol 3 ◽  
pp. 1-11 ◽  
Author(s):  
Johan Pohl ◽  
Christian Stahl ◽  
Karsten Albe
Keyword(s):  
Monte Carlo ◽  
Phase Diagrams ◽  
Short Range ◽  
Short Range Order ◽  
Surface Segregation ◽  
Order Parameters ◽  
Range Order ◽  
Platinum Concentration ◽  
Monte Carlo Simulation Study ◽  
Size Dependent

Nanoparticles of Pt–Rh were studied by means of lattice-based Monte Carlo simulations with respect to the stability of ordered D022- and 40-phases as a function of particle size and composition. By thermodynamic integration in the semi-grand canonical ensemble, phase diagrams for particles with a diameter of 7.8 nm, 4.3 nm and 3.1 nm were obtained. Size-dependent trends such as the lowering of the critical ordering temperature, the broadening of the compositional stability range of the ordered phases, and the narrowing of the two-phase regions were observed and discussed in the context of complete size-dependent nanoparticle phase diagrams. In addition, an ordered surface phase emerges at low temperatures and low platinum concentration. A decrease of platinum surface segregation with increasing global platinum concentration was observed, when a second, ordered phase is formed inside the core of the particle. The order–disorder transitions were analyzed in terms of the Warren–Cowley short-range order parameters. Concentration-averaged short-range order parameters were used to remove the surface segregation bias of the conventional short-range order parameters. Using this procedure, it was shown that the short-range order in the particles at high temperatures is bulk-like.

Calculation of Pairwise Effective Potentials in the Disordered Ni-22.5at.%Fe Alloy Using Model Potential Method with Account of Size Effect

2021 ◽  
Vol 323 ◽  
pp. 125-129
Author(s):  
Valentin Silonov ◽  
Lkhamsuren Enkhtor
Keyword(s):  
Size Effect ◽  
Short Range ◽  
Short Range Order ◽  
Potential Method ◽  
Model Potential ◽  
Order Parameters ◽  
Range Order ◽  
Disorder Phase Transition ◽  
Effective Potentials ◽  
Atomic Displacements

Pairwise effective potentials in first seventeen shells of the Ni-22.5at.%Fe alloy are calculated using model potential method with account of the linear size effect. Using obtained values of pairwise effective potentials, the short range order parameters on the first seventeen shells of alloy are calculated by Krivoglaz-Clapp-Moss method. The calculated values ​​of the short-range order parameters were fitted to the experimental values ​​by varying the parameters of static atomic displacements. Reliable value of critical temperature of order-disorder phase transition in Ni-22.5at.%Fe alloy was calculated using obtained meanings of pairwise effective potentials.

Temperature dependence of short-range-order parameters

1978 ◽  
Vol 21 (4) ◽  
pp. 454-458
Author(s):  
G. P. Revkevich ◽  
E. I. Bodneva
Keyword(s):  
Temperature Dependence ◽  
Short Range ◽  
Short Range Order ◽  
Order Parameters ◽  
Range Order

THE APPROACH TO PARAMAGNETIC SATURATION

1962 ◽  
Vol 40 (12) ◽  
pp. 1693-1702 ◽  
Author(s):  
Richard Stevenson
Keyword(s):  
External Field ◽  
Magnetic Moment ◽  
Short Range ◽  
Short Range Order ◽  
Field Method ◽  
Order Parameters ◽  
Range Order ◽  
Molecular Field ◽  
Paramagnetic Materials ◽  
High Fields

The process of paramagnetic saturation in real substances is considered by means of the molecular field method and by Smart's elaboration of the Oguchi method. The magnetic moment and short-range order parameters are calculated as a function of the external field. Some qualitative rules are obtained which describe general tendencies toward saturation. The possibility arises that paramagnetic materials in high fields may change into a state of greater stability by altering their exchange couplings.

Interdiffusion in Short-Wavelength Modulated Materials Studied by Monte-Carlo Simulations

1987 ◽  
Vol 103 ◽  
Author(s):  
M. Atzmon
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Interdiffusion Coefficient ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
One Dimensional ◽  
Interdiffusion Process ◽  
Limiting Value ◽  
Modulation Wavelength

ABSTRACTInterdiffusion in a two-dimensional compositionally modulated lattice has been studied by Monte-Carlo simulations. In the initial stages, the interdiffusion coefficient has been observed to change with time due to the development of short-range order simultaneously with the interdiffusion process. When the short-range order parameter approached its limiting value, the diffusion coefficient approached a constant value. The dependence of the interdiffusion coefficient on the modulation wavelength does not agree with the prediction of one-dimensional theories. For ordering alloy systems, the effective interdiffusion coefficient is positive, i.e., an initially present modulation decays in time, for all wavelengths.

Short-range Order Parameters in fcc Binary Alloys

2007 ◽  
pp. 145-158 ◽  
Author(s):  
J. S. Faulkner ◽  
Silvia Pella ◽  
Aurelian Rusanu ◽  
Yevgeniy Puzyrev
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Binary Alloys ◽  
Order Parameters ◽  
Range Order ◽  
Fcc Binary Alloys
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