Transitions in Critical Island Size in Metal (100) and (111) Homoepitaxy: A Self-Consistent Rate Equation Approach

1998 ◽  
Vol 528 ◽  
Author(s):  
Mihail N. Popescu ◽  
Jacques G. Amar ◽  
Fereydoon Family
Keyword(s):  
Rate Equation ◽  
Kinetic Monte Carlo ◽  
Island Size ◽  
Bond Model ◽  
Self Consistent ◽  
Standard Rate ◽  
Simulation Results ◽  
Small Clusters ◽  
Short Range Correlations ◽  
Good Agreement

AbstractA self-consistent rate equation (RE) approach to submonolayer growth for a restricted pair-bond model that is relevant to low and intermediate temperature metal (100) and (111) homoepitaxy is introduced. In contrast to previous standard rate equation results, the transition temperature from i = 1 to a higher critical island size is well predicted along with the average island and monomer densities. It is shown that the method's implicit introduction of short-range correlations between attachment/detachment rates, together with a careful estimate of the escape rates for small clusters, are important factors for a good agreement with the kinetic Monte Carlo simulation results.

scholarly journals Kinetic Monte Carlo Simulation of Clustering in an Al-Mg-Si-Cu Alloy

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4523
Author(s):  
Qilu Ye ◽  
Jianxin Wu ◽  
Jiqing Zhao ◽  
Gang Yang ◽  
Bin Yang
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Complex Interaction ◽  
Cu Alloy ◽  
Cu Alloys ◽  
Simulation Results ◽  
Small Clusters ◽  
First Time

The mechanism of the clustering in Al-Mg-Si-Cu alloys has been a long-standing controversial issue. Here, for the first time, the mechanism of the clustering in the alloy was investigated by a Kinetic Monte Carlo (KMC) approach. In addition, reversion aging (RA) was carried out to evaluate the simulation results. The results showed that many small-size clusters formed rapidly in the early stages of aging. With the prolongation of aging time, the clusters merged and grew. The small clusters formed at the beginning of aging in Al-Mg-Si-Cu alloy were caused by initial vacancies (quenching vacancies). The merging and decomposition of the clusters were mainly caused by the capturing of vacancies, and the clusters had a probability to decompose before reaching a stable size. After repeated merging and decomposition, the clusters reach stability. During RA, the complex interaction between the cluster merging and decomposition leaded to the partial irregular change of the hardness reduction and activation energy.

Irreversible Island Formation During Deposition: Island Size and Separation Distributions

1992 ◽  
Vol 280 ◽  
Author(s):  
M. C. Bartelt ◽  
M. C. Tringides ◽  
J. W. Evans
Keyword(s):  
Size Distribution ◽  
Rate Equation ◽  
Nucleation And Growth ◽  
Simplified Model ◽  
Island Size ◽  
Deposition Rates ◽  
Island Formation ◽  
Simulation Results ◽  
Precise Simulation

ABSTRACTWe present precise simulation results for a simplified model of irreversible nucleation and growth of islands during deposition. We characterize the scaling of the island and adatom densities, the complete island size distribution, and the adatom-island and island-island separation distributions, with the ratio of diffusion to deposition rates (for fixed coverages,θ<1). We also make some comparisons with rate equation predictions.

Self-Consistent Rate-Equation Approach to Nucleation and Growth in Point/Extended Island Models of 1-D Homoepitaxy

1999 ◽  
Vol 570 ◽  
Author(s):  
Jacques G. Amar ◽  
Mihail N. Popescu ◽  
Fereydoon Family
Keyword(s):  
Rate Equation ◽  
Kinetic Monte Carlo ◽  
Mean Field ◽  
Field Equations ◽  
Size Dependent ◽  
Coverage Dependence ◽  
Capture Zones ◽  
Mean Field Equations ◽  
Self Consistent ◽  
Monomer Density

ABSTRACTA self-consistent rate equation (RE) approach to submonolayer growth on a one-dimensional surface is presented. This approach explicitly takes into account the existence of gaps between clusters and can successfully predict the coverage dependence of the average densities of monomers N1, and clusters, N. It also implies an unusual dependence for the monomer-monomer capture number σ1 as a function of monomer density. To obtain the island size-distribution, a second set of mean-field equations is used describing the evolution of the size-dependent capture zones and leading to explicit size- and coverage-dependent capture numbers. The solution of this fully self-consistent RE approach is then compared with kinetic Monte Carlo results

scholarly journals Crossover from Dimer Nucleation to Adatom Exchange During Submonolayer Epitaxy

1995 ◽  
Vol 399 ◽  
Author(s):  
G.S. Bales
Keyword(s):  
Kinetic Monte Carlo ◽  
Mean Field ◽  
Nucleation And Growth ◽  
Rate Equations ◽  
Number Density ◽  
Dimer Formation ◽  
Island Size ◽  
Self Consistent ◽  
Kinetic Monte Carlo Simulations ◽  
Increasing Temperature

ABSTRACTThe nucleation and growth of islands in the early stages of epitaxial growth is studied with kinetic Monte Carlo Simulations and self-consistent mean field rate equations. Specifically, adatom exchange and irreversible dimer formation are allowed to compete equally as the origin of two-dimensional islands. The island size distribution and number density are found to satisfy a dynamic crossover scaling form. The critical island size evolves from one to zero with increasing temperature, decreasing flux, and increasing coverage.

Effects of Crystalline Microstructure on Epitaxial Morphology

1995 ◽  
Vol 399 ◽  
Author(s):  
Fereydoon Family ◽  
Jacques G. Amar
Keyword(s):  
Crystal Structure ◽  
Epitaxial Growth ◽  
Large Scale ◽  
Kinetic Monte Carlo ◽  
Island Size ◽  
The Past ◽  
Stages Of Growth ◽  
Kinetic Monte Carlo Simulations ◽  
Crystalline Microstructure ◽  
Good Agreement

ABSTRACTIn the past simulations of epitaxial growth have used solid-on-solid (SOS) models to simulate the crystalline structure of both the substrate and the growing crystal. These models have produced results in the early stages of growth in good agreement with experiments for a number of different quantities, including the island density and the island size distribution. For multilayer growth, however, there exists a competition between microscopic effects such as the Ehrlich-Schwoebel step barrier and the crystalline microstructure. Therefore, the crystal structure and geometry are important in determining the dynamics and evolution of epitaxial structure and morphology. We present the results of large-scale realistic kinetic Monte-Carlo simulations of multilayer epitaxial growth on fcc(100) and bcc(100) surfaces. The influence of crystal structure on the formation and coarsening of mounds and facets is discussed. We also discuss and compare our results with recent experiments.

scholarly journals Measuring Hydrometeors Using a Precipitation Microphysical Characteristics Sensor: Sampling Effect of Different Bin Sizes on Drop Size Distribution Parameters

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xichuan Liu ◽  
Taichang Gao ◽  
Yuntao Hu ◽  
Xiaojian Shu
Keyword(s):  
Drop Size ◽  
Rain Rate ◽  
Monte Carlo Model ◽  
Rain Gauge ◽  
Sampling Schemes ◽  
Distribution Parameters ◽  
Optimum Sampling ◽  
Simulation Results ◽  
The Impact ◽  
Good Agreement

In order to improve the measurement of precipitation microphysical characteristics sensor (PMCS), the sampling process of raindrops by PMCS based on a particle-by-particle Monte-Carlo model was simulated to discuss the effect of different bin sizes on DSD measurement, and the optimum sampling bin sizes for PMCS were proposed based on the simulation results. The simulation results of five sampling schemes of bin sizes in four rain-rate categories show that the raw capture DSD has a significant fluctuation variation influenced by the capture probability, whereas the appropriate sampling bin size and width can reduce the impact of variation of raindrop number on DSD shape. A field measurement of a PMCS, an OTT PARSIVEL disdrometer, and a tipping bucket rain Gauge shows that the rain-rate and rainfall accumulations have good consistencies between PMCS, OTT, and Gauge; the DSD obtained by PMCS and OTT has a good agreement; the probability of N0, μ, and Λ shows that there is a good agreement between the Gamma parameters of PMCS and OTT; the fitted μ-Λ and Z-R relationship measured by PMCS is close to that measured by OTT, which validates the performance of PMCS on rain-rate, rainfall accumulation, and DSD related parameters.

scholarly journals The influence of exocyclic lone pairs on the bonding and geometry of type A mesoionic rings

2021 ◽  
Author(s):  
Christopher Antony Ramsden ◽  
Wojciech Piotr Oziminski
Keyword(s):  
Ab Initio ◽  
Type A ◽  
Nbo Analysis ◽  
Ring Systems ◽  
X Ray ◽  
X Ray Crystallography ◽  
Bond Model ◽  
Lone Pairs ◽  
Mp2 Calculations ◽  
Good Agreement

AbstractBased on structures determined by X-ray crystallography, ab initio MP2 calculations on type A mesoionic rings give geometries in good agreement with observed values. A study of four mesoionic ring systems, each with exocyclic oxygen, nitrogen or carbon groups, shows that the presence and configuration of exocyclic lone pairs significantly influences the geometry and configurational preference. Using a localised bond model and NBO analysis, these effects are rationalised in terms of an anomeric interaction of lone pairs with the antibonding orbitals of adjacent σ bonds. In agreement with experiment, similar effects are calculated for pyran-2-imines.

scholarly journals Simulation and Experimental Study on Wear of U-Shaped Rings of Power Connection Fittings under Strong Wind Environment

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 735
Author(s):  
Songchen Wang ◽  
Xianchen Yang ◽  
Xinmei Li ◽  
Cheng Chai ◽  
Gen Wang ◽  
...  
Keyword(s):  
Abrasive Wear ◽  
Adhesive Wear ◽  
Surface Hardness ◽  
Wear Depth ◽  
Strong Wind ◽  
Wear Model ◽  
Wind Environment ◽  
Simulation Results ◽  
Oxidation Wear ◽  
Good Agreement

The objective of this study was to investigate the wear characteristics of the U-shaped rings of power connection fittings, and to construct a wear failure prediction model of U-shaped rings in strong wind environments. First, the wear evolution and failure mechanism of U-shaped rings with different wear loads were studied by using a swinging wear tester. Then, based on the Archard wear model, the U-shaped ring wear was dynamically simulated in ABAQUS, via the Umeshmotion subroutine. The results indicated that the wear load has an important effect on the wear of the U-shaped ring. As the wear load increases, the surface hardness decreases, while plastic deformation layers increase. Furthermore, the wear mechanism transforms from adhesive wear, slight abrasive wear, and slight oxidation wear, to serious adhesive wear, abrasive wear, and oxidation wear with the increase of wear load. As plastic flow progresses, the dislocation density in ferrite increases, leading to dislocation plugs and cementite fractures. The simulation results of wear depth were in good agreement with the test value of, with an error of 1.56%.

Isotope shift and hyperfine structure in the atomic spectrum of tin

1973 ◽  
Vol 332 (1588) ◽  
pp. 129-138 ◽  
Keyword(s):  
Stable Isotopes ◽  
Hyperfine Structure ◽  
Nuclear Charge ◽  
Light Sources ◽  
Atomic Spectrum ◽  
Nuclear Charge Distribution ◽  
Fabry Perot ◽  
Self Consistent ◽  
Structure Constants ◽  
Good Agreement

Three lines in the atomic spectrum of tin, λ 3262 Å, λ 3283 Å and λ 6454Å have been studied in emission under high resolution with the use of light sources containing enriched isotopic samples. Results are reported for isotope shifts in these lines for the abundant stable isotopes ( A ≽ 116). Pressure-scanned Fabry–Perot etalons provided the necessary resolution; the spectrograms for λ 6454 Å were recorded and analysed by digital techniques, and for this line hyperfine structure constants required in the interpretation of the data were also evaluated. The results for the three lines are not in good agreement with earlier work, but are shown to be self-consistent by means of a King plot. Their interpretation in terms of the nuclear charge distribution is considered in the following paper.

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