Comment on “Monte Carlo simulations for a Lotka-type model with reactant diffusion and interactions”

2002 ◽  
Vol 65 (3) ◽  
Author(s):  
Vladimir P. Zhdanov
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Type Model

Triple-Defect B2 Binary Intermetallics: Bragg-Williams Solution and Monte Carlo Simulations

2009 ◽  
Vol 289-292 ◽  
pp. 361-368 ◽  
Author(s):  
Andrzej Biborski ◽  
L. Zosiak ◽  
Rafal Abdank-Kozubski
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Vacancy Concentration ◽  
A Priori ◽  
Equilibrium Concentration ◽  
Pair Interaction ◽  
Type Model ◽  
Interaction Energies ◽  
Atomic Pair ◽  
Antisite Defects

Surprisingly low rate of “order-order” kinetics in stoichiometric NiAl intermetallic known of very high vacancy concentration suggested a specific triple-defect mechanism of ordering/disordering in this system [1]. This mechanism implies a correlation between the concentrations of antisite defects and vacancies; the latters being trapped in triple defects and thus, inactive as atomic migration agents. The process was modelled by means of Monte Carlo (MC) simulations recognised as a powerful tool for such tasks [2], but requiring now the implementation of thermal vacancy thermodynamics. Temperature dependence of vacancy concentration in an AB B2 binary system was determined within an Ising-type model solved first in Bragg-Williams approximation [3] and then by means of MC simulation of a Grandcanonical Ensemble. Without any a priori assumptions concerning the formation of particular types of point defects the model yielded temperature domains where the concentrations of antisite defects and vacancies were proportional. The effect associated with the formation of triple defects appeared for specific values of atomic pair-interaction energies. Moreover, non-stoichiometric A-B systems with the same atomic pair-interaction energies showed the existence of constitutional vacancies at low temperatures. Monte Carlo simulations of “order-order” (disordering) kinetics in B2 AB systems modelled with triple-defect-promoting atomic pair-interaction energies were run with temperature-dependent concentra-tion (i.e. number) of vacancies given by the above model. The simulated relaxations showed two stages: (i) rapid formation of triple defects engaging almost all vacancies present in the system, (ii) very slow process of further generation of antisite defects until the equilibrium concentration was reached. The result reproduced very well the experimental observations [1].

Size-Induced Freezing Effect in Monte-Carlo Simulations of Phase Separation Kinetics in Nanoparticles

2008 ◽  
Vol 277 ◽  
pp. 167-175 ◽  
Author(s):  
A.S. Shirinyan ◽  
D.V. Lubyanskyy
Keyword(s):  
Monte Carlo ◽  
Phase Separation ◽  
Monte Carlo Simulations ◽  
Monte Carlo Sampling ◽  
Type Model ◽  
Two Dimensional ◽  
Vacancy Mechanism ◽  
Phase Separation Kinetics ◽  
Kinetics Of ◽  
Separation Kinetics

The separation kinetics in a binary nanoparticle is studied by means of two-dimensional Monte-Carlo sampling and Ising-type model, where the species exchange positions due to vacancy mechanism. The model is developed in case of a free nanoparticle with a coating shell. The kinetics is shown to depend on the size of a nanosystem. We demonstrate a distinct size-induced freezing effect on kinetics of separation.

Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

1996 ◽  
Vol 54 ◽  
pp. 478-479
Author(s):  
Matthew T. Johnson ◽  
Ian M. Anderson ◽  
Jim Bentley ◽  
C. Barry Carter
Keyword(s):  
Monte Carlo ◽  
Quantitative Analysis ◽  
Monte Carlo Simulations ◽  
Cross Section ◽  
Spatial Resolution ◽  
Low Voltage ◽  
Magnesium Ferrite ◽  
X Ray ◽  
Interaction Volume ◽  
Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

MONTE CARLO SIMULATIONS OF ELECTRON DRIFT VELOCITIES IN THE NOBLE GASES AND THEIR MIXTURES

1979 ◽  
Vol 40 (C7) ◽  
pp. C7-63-C7-64
Author(s):  
A. J. Davies ◽  
J. Dutton ◽  
C. J. Evans ◽  
A. Goodings ◽  
P.K. Stewart
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Noble Gases ◽  
Electron Drift
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