scholarly journals Kinetic Monte Carlo Investigation of the Effects of Vacancy Pairing on Oxygen Diffusivity in Yttria-Stabilized Zirconia

2011 ◽  
Vol 1331 ◽  
Author(s):  
Brian S. Good
Keyword(s):  
Monte Carlo ◽  
Solid Electrolytes ◽  
Oxygen Vacancies ◽  
Nearest Neighbor ◽  
Kinetic Monte Carlo ◽  
High Energy ◽  
Oxygen Diffusivity ◽  
Low Concentrations ◽  
Migration Barriers ◽  
Monte Carlo Investigation

ABSTRACTYttria-stabilized zirconia’s high oxygen diffusivity and corresponding high ionic conductivity, and its structural stability over a broad range of temperatures, have made the material of interest for use in a number of applications, for example, as solid electrolytes in fuel cells. At low concentrations, the stabilizing yttria also serves to increase the oxygen diffusivity through the presence of corresponding oxygen vacancies, needed to maintain charge neutrality. At higher yttria concentration, however, diffusivity is impeded by the larger number of relatively high energy migration barriers associated with yttrium cations. In addition, there is evidence that oxygen vacancies preferentially occupy nearest-neighbor sites around either dopant or Zr cations, further affecting vacancy diffusion. We present the results of ab initio calculations that indicate that it is energetically favorable for oxygen vacancies to occupy nearest-neighbor sites adjacent to Y ions, and that the presence of vacancies near either species of cation lowers the migration barriers. Kinetic Monte Carlo results from simulations incorporating this effect are presented and compared with results from simulations in which the effect is not present.

Kinetic Monte Carlo Simulations of Strain-Induced Nanopatterning on Hexagonal Surfaces

2002 ◽  
Vol 731 ◽  
Author(s):  
M.I. Larsson ◽  
B. Lee ◽  
R. Sabiryanov ◽  
K. Cho ◽  
W. Nix ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Saddle Point ◽  
Self Assembly ◽  
Nearest Neighbor ◽  
Kinetic Monte Carlo ◽  
Research Field ◽  
Surface Strain ◽  
Manufacturing Cost ◽  
Component Size ◽  
Quantum Mechanical Effects

AbstractGuided self assembly of periodic arrays of quantum dots has recently emerged as an important research field not only to reduce component size and manufacturing cost but also to explore and apply quantum mechanical effects in novel nanodevices. The intention of this kinetic Monte Carlo (KMC) simulation study is to investigate self-organized nanopatterning on hexagonal surfaces for relaxed periodic surface strain fields applied to Pt(111) epitaxy. The KMC model is a full diffusion bond-counting model including nearest neighbor as well as second-nearest neighbor interactions with an event catalogue consisting of 8989 events modeling the effect of the biaxial surface strain field. The strain dependence of the fcc site and the saddle point for a Pt adatom migrating on top of the Pt(111) surface is calculated using the embedded atom method. Both the valley and the saddle point energies show an excellent linear dependence on the strain. These results are applied in the KMC model. The surface strain in this study is caused by a hexagonal network of dislocations at the interface between the substrate and a mismatched epitaxial layer. How the selforganization of deposited atoms is influenced by the surface strain will be addressed.

Monte Carlo simulations of long-range order kinetics in B2 phases

1995 ◽  
Vol 10 (3) ◽  
pp. 591-595 ◽  
Author(s):  
K. Yaldram ◽  
V. Pierron-Bohnes ◽  
M.C. Cadeville ◽  
M.A. Khan
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Nearest Neighbor ◽  
Vacancy Concentration ◽  
Relaxation Times ◽  
Nearest Neighbors ◽  
Migration Energy ◽  
Ordering Kinetics ◽  
Migration Barriers ◽  
Temperature Dependences

The thermodynamic parameters that drive the atomic migration in B2 alloys are studied using Monte-Carlo simulations. The model is based on a vacancy jump mechanism between nearest neighbor sites, with a constant vacancy concentration. The ordering energy is described through an Ising Hamiltonian with interaction potentials between first and second nearest neighbors. Different migration barriers are introduced fur A and B atoms. The results of the simulations compare very well with those of experiments. The ordering kinetics are well described by exponential-like behaviors with two relaxation times whose temperature dependences are Arrhenius laws yielding effective migration energies. The ordering energy contributes significantly to the total migration energy.

A combined fluid dynamic and 3D kinetic Monte Carlo investigation of the selective deposition of GaAs and InP

2004 ◽  
Vol 272 (1-4) ◽  
pp. 52-58 ◽  
Author(s):  
Maurizio Rondanini ◽  
Carlo Cavallotti ◽  
Davide Moscatelli ◽  
Maurizio Masi ◽  
Sergio Carrà
Keyword(s):  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Fluid Dynamic ◽  
Selective Deposition ◽  
Monte Carlo Investigation

scholarly journals Kinetic Monte Carlo Simulations of Oxygen Diffusion in Environmental Barrier Coating Materials

MRS Advances ◽  
2018 ◽  
Vol 3 (10) ◽  
pp. 511-518 ◽  
Author(s):  
Brian S. Good
Keyword(s):  
Monte Carlo ◽  
Water Vapor ◽  
Bond Coat ◽  
Oxygen Diffusion ◽  
Kinetic Monte Carlo ◽  
Ceramic Matrix Composite ◽  
Low Oxygen ◽  
Coating Materials ◽  
Environmental Barrier ◽  
Oxygen Diffusivity

ABSTRACTCeramic Matrix Composite (CMC) materials are of interest for use in next-generation turbine engine components, offering a number of significant advantages, including reduced weight and high operating temperatures. However, in the hot environment in which such components operate, the presence of water vapor can lead to corrosion and recession, limiting the useful life of the components. Such degradation can be reduced through the use of Environmental Barrier Coatings (EBCs) that limit the amount of oxygen and water vapor reaching the component. Candidate EBC materials include Yttrium and Ytterbium silicates. In this work we present results of kinetic Monte Carlo (kMC) simulations of oxygen diffusion, via the vacancy mechanism, in Yttrium and Ytterbium disilicates, along with a brief discussion of interstitial diffusion.An EBC system typically includes a bond coat located between the EBC and the component surface. Bond coat materials are generally chosen for properties other than low oxygen diffusivity, but low oxygen diffusivity is nevertheless a desirable characteristic, as the bond coat could provide some additional component protection, particularly in the case where cracks in the coating system provide a direct path from the environment to the bond coat interface. We have therefore performed similar kMC simulations of oxygen diffusion in this material.

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