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.

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.

scholarly journals Migration of Zeolite-Encapsulated Pt and Au Under Reducing Atmospheres

2021 ◽  
Author(s):  
Dianwei Hou ◽  
Christopher Heard
Keyword(s):  
Monte Carlo ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Noble Metals ◽  
Kinetic Monte Carlo ◽  
Pore System ◽  
Kinetic Monte Carlo Simulations ◽  
Zeolite Lta ◽  
Metal Migration ◽  
Energy Surfaces

Unbiased density functional global optimisation calculations, followed by kinetic Monte Carlo simulations are used to enumerate the potential energy surfaces for migration of noble metals Pt and Au inside the pore system of siliceous zeolite LTA. The effects of reducing adsorbates CO and H2 are determined. It is found that the two metals differ significantly in the strength and type of interaction with the framework, with strong, framework breaking interactions between Pt and and the zeolite, but only weak dispersive interactions between Au and the zeolite. Adsorbates are found to dramatically interfere with Pt-framework binding, leading to poorer atom-trapping, enhanced metal migration and faster equilibration.

Consensus formation in continuous opinion dynamics on quasiperiodic lattices

2019 ◽  
Vol 31 (01) ◽  
pp. 2050012
Author(s):  
T. F. A. Alves ◽  
F. W. S. Lima ◽  
A. Macedo-Filho ◽  
G. A. Alves
Keyword(s):  
Kinetic Monte Carlo ◽  
Finite Size ◽  
Opinion Dynamics ◽  
Universality Class ◽  
External Noise ◽  
Continuous Phase ◽  
Formation Model ◽  
Consensus Formation ◽  
Kinetic Monte Carlo Simulations ◽  
Binder Cumulant

We studied the Biswas–Chatterjee–Sen (BCS) consensus formation model, also known as the Kinetic Continuous Opinion Dynamics (KCOD) model on quasiperiodic lattices by using Kinetic Monte Carlo simulations and Finite Size Scaling technique. Our results are consistent with a continuous phase transition, controlled by an external noise. We obtained the order parameter [Formula: see text], defined as the averaged opinion, the fourth-order Binder cumulant [Formula: see text] and susceptibility [Formula: see text] as functions of the noise parameter. We estimated the critical noises for Penrose and Ammann–Beenker lattices. We also considered seven-fold and nine-fold quasiperiodic lattices and estimated the respective critical noises as well. Irrespective of rotational and translational long-range order of the lattice, the system falls in the same universality class of the two-dimensional Ising model. Quasiperiodic order is irrelevant and it does not change any critical exponents for BCS model.

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.

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.

Atomistic modeling of Ru nanocluster formation on graphene/Ru(0001): Thermodynamically versus kinetically directed-assembly

2013 ◽  
Vol 1498 ◽  
pp. 249-254 ◽  
Author(s):  
Y. Han ◽  
A. K. Engstfeld ◽  
C.-Z. Wang ◽  
L. D. Roelofs ◽  
R. J. Behm ◽  
...  
Keyword(s):  
Density Functional ◽  
Lattice Gas ◽  
Kinetic Monte Carlo ◽  
Directed Assembly ◽  
Height Distribution ◽  
Functional Theory ◽  
Atomistic Lattice ◽  
Lattice Gas Models ◽  
Mean Size ◽  
Kinetic Monte Carlo Simulations

ABSTRACTAtomistic lattice-gas models for thermodynamically and kinetically directed assembly are applied to Ru nanocluster formation on a monolayer of graphene supported on Ru(0001) at 309 K. Nanocluster density, mean size, height distribution, and spatial ordering are analyzed by kinetic Monte Carlo simulations. Both models can reproduce the experimental data, but additional density functional theory analysis favors the former.

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