Model for the catalytic reduction of no on a surface with species desorption and impurities that cannot desorb

2021 ◽  
Author(s):  
E. J. Hernández ◽  
G. M. Buendía
Keyword(s):  
Catalytic Reduction ◽  
Kinetic Monte Carlo ◽  
Dynamical Behavior ◽  
Square Lattice ◽  
Modified Model ◽  
Reduction Of No ◽  
Large Fluctuations ◽  
Long Time ◽  
Kinetic Monte Carlo Simulations ◽  
The Stability

The dynamical behavior of a modified Yaldram–Khan model for the catalytic reduction of NO on a surface is studied by Kinetic Monte Carlo simulations. In this modified model, temperature effects are incorporated as desorption rates of the N and CO species. How the presence of contaminants in the gas phase affects the catalytic process is also analyzed by including impurities that can be adsorbed on the lattice and once there remain inert. When N desorption is included, a reactive window appears that is not present in the original YK model on a square lattice. When CO desorption is added large fluctuations appear in the coverages, the system can take a long time to stabilize, during this period, a long lasting reactive state exists that disappears when the stability is reached. When nondesorbing impurities are added, the discontinuous transition to a CO poisoned phase that presents the original YK model disappears, the coverages become continuous, and a nonreactive steady-state is rapidly reached.

Step-Edge Barriers on GaAs(001)

1995 ◽  
Vol 399 ◽  
Author(s):  
P. Šmilauer ◽  
D.D. Vvedensky
Keyword(s):  
Kinetic Monte Carlo ◽  
Step Edge ◽  
Layer By Layer ◽  
Vicinal Surfaces ◽  
Activation Barriers ◽  
Long Time ◽  
Kinetic Monte Carlo Simulations ◽  
Simulated Surface ◽  
Constant Slope ◽  
Surface Morphologies

ABSTRACTWe investigate growth of GaAs(001) using kinetic Monte Carlo simulations of a very simple atomistic solid-on-solid model. The key features of this model are a short-range incorporation process of freshly deposited atoms and additional activation barriers to interlayer transport. Both are required to obtain close agreement between measured electron-diffraction intensities and simulated surface step densities during growth and post-growth equilibration on vicinal surfaces. This model is used to study long-time evolution of the surface morphology. Large pyramid-like features develop during growth on a singular surface which coarsen in time while maintaining an approximately constant slope. Growth on a vicinal surface is also found to be unstable. Simulated surface morphologies are compared with recent work using atomic-force microscopy. Finally, we show how a suitably modified version of this model helps to explain the recently observed phenomenon of re-entrant layer-by-layer chemical-beam etching of a singular GaAs(001) surface. The central features responsible for this behavior are the site selectivity of the etching process combined with step-edge barriers to interlayer adatom migration.

Examination of the Effect of Vacancy Detachment Rates on Kinetic Monte Carlo Simulations of bcc Metals

MRS Advances ◽  
2016 ◽  
Vol 1 (35) ◽  
pp. 2489-2494 ◽  
Author(s):  
Richard T Hoffman ◽  
Alexander P Moore ◽  
Chaitanya S Deo
Keyword(s):  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Void Formation ◽  
Binding Energies ◽  
Size Dependent ◽  
Bcc Metals ◽  
Bcc Lattice ◽  
Long Time ◽  
Kinetic Monte Carlo Simulations ◽  
Dynamics Simulations

ABSTRACTA Kinetic Monte Carlo simulation, using a modified version of the SPPARKS code, of simple defects and complex vacancy clusters was run on a bcc lattice. In this simulation the complexity of void formation was varied by introducing a detachment rate for individual vacancies leaving the void and either treating this value as constant for all size voids or having this value be dependent on the size of the void. Molecular Dynamics simulations were used to determine the binding energies of vacancies for voids of varying size. The simulation was then run over long time periods to determine the number of defects in the simulation under irradiation conditions. It was found that the additional complexity of size dependent void detachment rates had little effect on the defect concentrations and thus a constant barrier should be sufficient for simulations of voids in bcc metals.

scholarly journals Kinetic Monte Carlo Simulations of Electrochemical Oxidation and Reduction of Pt(111)

2019 ◽  
Vol 166 (16) ◽  
pp. H888-H896
Author(s):  
J. Erlebacher ◽  
J. Kubal ◽  
Z. Zeng ◽  
J. Greeley ◽  
K. Struk ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Electrochemical Oxidation ◽  
Kinetic Monte Carlo ◽  
Complex Surface ◽  
Surface Roughening ◽  
Morphological Response ◽  
Kinetic Monte Carlo Simulations ◽  
Place Exchange ◽  
The Stability

Kinetic Monte Carlo simulations of electrochemical oxidation and reduction are presented that match many features of the experimentally observed electrochemical and morphological response of Pt(111). Included in the simulation are all relevant microscopic transitions, including the formation of Pt-OH and Pt-O from Pt, surface diffusion of all three species, as well as an effective place exchange diffusion at high potential. A detailed description of this approach to modeling such a complex surface is also presented. Overall, it is found that many features of the Pt(111) CV, including hydroxylation, hysteresis, and surface roughening, can be correlated to events associated with n-coordinated surface species, such as the hydroxylation wave corresponding to a one-electron oxidation of 9-coordinated terrace sites. Oxidation to Pt-O species at potentials above 1.0 V are shown to correlate to the presence of growing surface roughness, and the simulations suggest the onset of Pt-O formation in steady-state cyclic voltammetry is dominated by the oxidation of 8-coordinated step edges rather than terrace sites. Implications for the stability of Pt(111) catalysts after thousands of voltammetric cycles are discussed.

scholarly journals COMPLEX BEHAVIOR IN SIMPLE MODELS OF BIOLOGICAL COEVOLUTION

2009 ◽  
Vol 20 (09) ◽  
pp. 1387-1397 ◽  
Author(s):  
PER ARNE RIKVOLD
Keyword(s):  
Kinetic Monte Carlo ◽  
Dynamical Behavior ◽  
Individual Species ◽  
Predator Prey ◽  
Population Sizes ◽  
Kinetic Monte Carlo Simulations ◽  
Predator Prey Models ◽  
Power Law Distributions ◽  
Adaptive Foraging ◽  
Type Ii Functional Response

We explore the complex dynamical behavior of simple predator-prey models of biological coevolution that account for interspecific and intraspecific competition for resources, as well as adaptive foraging behavior. In long kinetic Monte Carlo simulations of these models we find quite robust 1/f-like noise in species diversity and population sizes, as well as power-law distributions for the lifetimes of individual species and the durations of quiet periods of relative evolutionary stasis. In one model, based on the Holling Type II functional response, adaptive foraging produces a metastable low-diversity phase and a stable high-diversity phase.

Atomistic Modeling of III-V Semiconductors: Thermodynamic Equilibrium and Growth Kinetics

2001 ◽  
Vol 701 ◽  
Author(s):  
Frank Grosse ◽  
William Barvosa-Carter ◽  
Jennifer J. Zinck ◽  
Mark F. Gyure
Keyword(s):  
Thermodynamic Equilibrium ◽  
Growth Kinetics ◽  
Density Functional ◽  
Kinetic Monte Carlo ◽  
Continuous Phase ◽  
Determining Factors ◽  
Equilibrium And Kinetics ◽  
Kinetic Monte Carlo Simulations ◽  
The Stability ◽  
Stable Reconstruction

ABSTRACTGrowth kinetics and thermodynamic equilibrium can both be determining factors at different stages of III-V semiconductor heteroepitaxy. We study their interplay, employing kinetic Monte Carlo simulations for the InAs(001) surface. The simulation contains atomistic details of both species, including the stability of different reconstructions and their kinetics. The behavior of the surface in thermodynamic equilibrium, including different reconstructions, is determined exclusively by extensive total energy calculations employing ab initio density functional theory. The continuous phase transition between the α2(2x4) and β2(2x4), predicted by theory, is confirmed by experiment. At full layer coverage, a recovery of the stable reconstruction is observed. The different time scales associated with As2 and In are discussed with respect to equilibrium and kinetics.

Atomistic Modeling of III-V Semiconductors: Thermodynamic Equilibrium and Growth Kinetics

2001 ◽  
Vol 692 ◽  
Author(s):  
Frank Grosse ◽  
William Carter-Barvosa ◽  
Jennifer J. Zinck ◽  
Mark F. Gyure
Keyword(s):  
Thermodynamic Equilibrium ◽  
Growth Kinetics ◽  
Density Functional ◽  
Kinetic Monte Carlo ◽  
Continuous Phase ◽  
Determining Factors ◽  
Equilibrium And Kinetics ◽  
Kinetic Monte Carlo Simulations ◽  
The Stability ◽  
Stable Reconstruction

AbstractGrowth kinetics and thermodynamic equilibrium can both be determining factors at different stages of III-V semiconductor heteroepitaxy. We study their interplay, employing kinetic Monte Carlo simulations for the InAs(001) surface. The simulation contains atomistic details of both species, including the stability of different reconstructions and their kinetics. The behavior of the surface in thermodynamic equilibrium, including different reconstructions, is determined exclusively by extensive total energy calculations employing ab initio density functional theory. The continuous phase transition between the α?(2×4) and β?(2×4), predicted by theory, is confirmed by experiment. At full layer coverage, a recovery of the stable reconstruction is observed. The different time scales associated with As2 and In are discussed with respect to equilibrium and kinetics.

Computer Simulation of Microstructure Evolution of Fe-Cu Alloy during Thermal Ageing

2006 ◽  
Vol 306-308 ◽  
pp. 917-922
Author(s):  
Akiyuki Takahashi ◽  
Naoki Soneda ◽  
Masanori Kikuchi
Keyword(s):  
Computer Simulation ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Numerical Models ◽  
Kinetic Monte Carlo ◽  
Thermal Ageing ◽  
Vacancy Clusters ◽  
Cu Alloy ◽  
Long Time ◽  
Kinetic Monte Carlo Simulations

This paper describes a computer simulation of thermal ageing process in Fe-Cu alloy. In order to perform accurate numerical simulation, firstly, we make numerical models of the diffusion and dissociation of Cu and Cu-vacancy clusters. This modeling was performed with kinetic lattice Monte Carlo method, which allows us to perform long-time simulation of vacancy diffusion in Fe-Cu dilute alloy. The model is input to the kinetic Monte Carlo method, and then, we performed the kinetic Monte Carlo simulation of the thermal ageing in the Fe-Cu alloy. The results of the KMC simulations tell us that the our new models describes well the rate and kinetics of the diffusion and dissociation of Cu and Cu-vacancy clusters, and works well in the kinetic Monte Carlo simulations. Finally, we discussed the further application of these numerical models.

Dynamics of Atomic Ordering in Bulk and Thin Film Intermetallic Alloys: A Complementary Approach to Atomic Migration

2008 ◽  
Vol 1128 ◽  
Author(s):  
Wolfgang Pfeiler ◽  
Wolfgang Püschl ◽  
Chaisak Issro ◽  
Rafal Kozubski ◽  
Veronique Pierron-Bohnes
Keyword(s):  
Structural Changes ◽  
Materials Science ◽  
Kinetic Monte Carlo ◽  
Atomic Order ◽  
Intermetallic Alloys ◽  
Technical Application ◽  
Complementary Approach ◽  
Kinetic Monte Carlo Simulations ◽  
The Stability ◽  
Degree Of Order

AbstractOne of the foremost challenges in today's materials science is the design and development of materials with physical properties customized for technical application. Due to their excellent corrosion resistance and their advantageous mechanical and in many cases also magnetic properties, intermetallic alloys are among the most important materials of the 21st century. Most of their outstanding qualities are linked to long-range order, the fact that unlike atoms are preferred as neighbours, which then segregate to different sublattices. In most intermetallics atomic order persists up to rather high temperatures, if not up to melting. However, connected with the entropy gain, the degree of order depends on temperature and thereby the stability of the designed beneficial materials properties is affected. By monitoring changes in the degree of atomic order an access to atom migration is gained, which is complementary to the usual diffusion experiments, where the degree of order is not changed on average. It is shown in this review on some selected examples how an adequate thermal treatment of the samples in combination with the experimental approach gives detailed information on atom jump mechanisms and structural changes, especially if experiment is combined with up-to-date kinetic Monte Carlo simulations.

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