scholarly journals Kinetic Monte Carlo (KMC) Algorithm for Nanocrystals

2021 ◽  
Author(s):  
◽  
Sione Paea
Keyword(s):  
Monte Carlo ◽  
Crystal Growth ◽  
Gas Phase ◽  
Surface Diffusion ◽  
Ostwald Ripening ◽  
Kinetic Monte Carlo ◽  
Undercooled Melt ◽  
Diffusion Rates ◽  
Macroscopic Continuum ◽  
Surrounding Liquid

<p>This thesis uses the kinetic Monte Carlo (KMC) algorithm to examine the growth morphology and structure of nanocrystals. Crystal growth in a supersaturated gas of atoms and in an undercooled binary melt is investigated. First, in the gas phase, the interplay of the deposition and surface diffusion rates is studied. Then, the KMC algorithm is refined by including solidification events and finally, by adding diffusion in the surrounding liquid. A new algorithm is developed for modelling solidification from an undercooled melt. This algorithm combines the KMC method, which models the change in shape of the crystal during growth, with a macroscopic continuum method that tracks the diffusion of material through solution towards the crystal. For small length and time scales, this approach provides simple, effective front tracking with fully resolved atomistic detail of the crystal-melt interface. Anisotropy is included in the model as a surface diffusion process and the growth rate of the crystal is found to increase monotonically with increase in the surface anisotropy value. The method allows for the study of multiple crystal nuclei and Ostwald ripening. This method will aid researchers to explain why certain crystal shapes form under particular conditions during growth, and may enable nanotechnologists to design techniques for growing nanocrystals with specific shapes for a variety of applications, from catalysis to the medicine field and electronics industry. This will lead to a better understanding of the atomistic process of crystal growth at the nanoscale.</p>

scholarly journals Kinetic Monte Carlo (KMC) Algorithm for Nanocrystals

2021 ◽  
Author(s):  
◽  
Sione Paea
Keyword(s):  
Monte Carlo ◽  
Crystal Growth ◽  
Gas Phase ◽  
Surface Diffusion ◽  
Ostwald Ripening ◽  
Kinetic Monte Carlo ◽  
Undercooled Melt ◽  
Diffusion Rates ◽  
Macroscopic Continuum ◽  
Surrounding Liquid

<p>This thesis uses the kinetic Monte Carlo (KMC) algorithm to examine the growth morphology and structure of nanocrystals. Crystal growth in a supersaturated gas of atoms and in an undercooled binary melt is investigated. First, in the gas phase, the interplay of the deposition and surface diffusion rates is studied. Then, the KMC algorithm is refined by including solidification events and finally, by adding diffusion in the surrounding liquid. A new algorithm is developed for modelling solidification from an undercooled melt. This algorithm combines the KMC method, which models the change in shape of the crystal during growth, with a macroscopic continuum method that tracks the diffusion of material through solution towards the crystal. For small length and time scales, this approach provides simple, effective front tracking with fully resolved atomistic detail of the crystal-melt interface. Anisotropy is included in the model as a surface diffusion process and the growth rate of the crystal is found to increase monotonically with increase in the surface anisotropy value. The method allows for the study of multiple crystal nuclei and Ostwald ripening. This method will aid researchers to explain why certain crystal shapes form under particular conditions during growth, and may enable nanotechnologists to design techniques for growing nanocrystals with specific shapes for a variety of applications, from catalysis to the medicine field and electronics industry. This will lead to a better understanding of the atomistic process of crystal growth at the nanoscale.</p>

Kinetic Monte Carlo study of crystal growth from solution

2001 ◽  
Vol 138 (3) ◽  
pp. 250-263 ◽  
Author(s):  
Mirosława Rak ◽  
Marek Izdebski ◽  
Andrzej Brozi
Keyword(s):  
Monte Carlo ◽  
Crystal Growth ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Study ◽  
Growth From Solution

A hybrid continuum/kinetic Monte Carlo model for surface diffusion

2004 ◽  
Vol 365 (1-2) ◽  
pp. 66-72 ◽  
Author(s):  
S.P.A. Gill ◽  
P.E. Spencer ◽  
A.C.F. Cocks
Keyword(s):  
Monte Carlo ◽  
Surface Diffusion ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Model

Computational Investigation of Selective MOVPE of AlxGa1-xAs in Presence of Hcl

2001 ◽  
Vol 701 ◽  
Author(s):  
Maria Nemirovskaya ◽  
Carlo Cavallotti ◽  
Klavs Jensen
Keyword(s):  
Fluid Dynamics ◽  
Monte Carlo ◽  
Transition State ◽  
Gas Phase ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Model ◽  
Operating Conditions ◽  
Morphology Evolution ◽  
Computational Investigation ◽  
Dynamics Simulations

ABSTRACTThe deposition of AlGaAs in the presence of HCl was investigated at the macroscopic and mesoscopic scales. Fluid dynamics simulations were first performed in order to study the dependence of the deposition rate on the operating conditions. Unknown gas phase and surface kinetic parameters were estimated by quantum chemistry and transition state computations. The fluxes of all species to the surface were thus computed and provided the input to a kinetic Monte Carlo model used to investigate the morphology evolution of the film.

scholarly journals Monte Carlo Simulation of Adsorption Processes on Heterogeneous Crystal Surfaces

2021 ◽  
Author(s):  
◽  
Leila Rajabibonab
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Crystal Growth ◽  
Block Copolymer ◽  
Crystal Surface ◽  
Kinetic Monte Carlo ◽  
Effective Rate ◽  
The Other ◽  
Surface Energies ◽  
Adsorption Processes

<p>The simulation of adsorption processes on a heterogeneous crystal surface is the main interest of this thesis. Two applications of this event have been developed with Kinetic Monte Carlo simulation. One is how to control the crystal growth by macromolecules and the other is how to measure the effective rate of interactions near a crystal surface. The first part of this thesis, considers the effective rate of catalytic conversion on a heterogeneous catalytic surface. We assume the crystal surface has two types of active site, one is neutral and the other one is highly active. We compared our result from simulation with the analytical method that is given by the homogenization theory. Our result revealed the importance of patterns of surface energies and the size of them on reaction rate.  In the second project we consider the adsorption of a homopolymer chain on a crystal surface with two types of surface energies in order to limit the growth of one site and let the other sites grow more. We developed a new Kinetic Monte Carlo simulation method in this part, which was also applied to block copolymer chains that are more complex than a homo-polymer chain. Using this method four important phases of the polymer chains at high temperatures and also the free energies of the system across different patterns of active sites have been found. We tested different types of co-polymers to find the most differentiative block copolymer for controlling the crystal growth.</p>

Kinetic Monte Carlo Simulations of Ge Segregation During Epitaxial Growth of Si-SixGel-x Heterostructures

1994 ◽  
Vol 340 ◽  
Author(s):  
J. Deppe ◽  
J. V. Lill ◽  
D. J. Godbey ◽  
K. D. Hobart
Keyword(s):  
Monte Carlo ◽  
Surface Diffusion ◽  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
Film Growth ◽  
Kinetic Monte Carlo ◽  
Growth Surface ◽  
Germanium Surface ◽  
Specific Step ◽  
Kinetic Monte Carlo Simulations

ABSTRACTThe temperature dependence of germanium surface segregation during growth by solid source SiGe molecular beam epitaxy was studied by x-ray photoelectron spectroscopy and kinetic Monte Carlo (KMC) modeling. Germanium segregation persisted at temperatures 60ºC below that predicted by a two-state exchange model. KMC simulations, where film growth, surface diffusion, and surface segregation are modeled consistently, successfully describe the low temperature segregation of germanium. Realistic descriptions of MBE must follow the physical rates of the growth, surface diffusion, and surface segregation processes. A specific, step mediated exchange mechanism is also considered and shown to lead to surface segregation. While this model of Ge segregation seems possible, more work is necessary to obtain a consistent set of energy barriers.

scholarly journals Microscopic Rate Constants of Crystal Growth from Molecular Dynamic Simulations Combined with Metadynamics

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Dániel Kozma ◽  
Gergely Tóth
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Free Energy ◽  
Crystal Growth ◽  
Rate Constants ◽  
Kinetic Monte Carlo ◽  
State Theory ◽  
Free Energy Surface ◽  
Kinetic Monte Carlo Simulation

Atomistic simulation of crystal growth can be decomposed into two steps: the determination of the microscopic rate constants and a mesoscopic kinetic Monte Carlo simulation. We proposed a method to determine kinetic rate constants of crystal growth. We performed classical molecular dynamics on the equilibrium liquid/crystal interface of argon. Metadynamics was used to explore the free energy surface of crystal growth. A crystalline atom was selected at the interface, and it was displaced to the liquid phase by adding repulsive Gaussian potentials. The activation free energy of this process was calculated as the maximal potential energy density of the Gaussian potentials. We calculated the rate constants at different interfacial structures using the transition state theory. In order to mimic real crystallization, we applied a temperature difference in the calculations of the two opposite rate constants, and they were applied in kinetic Monte Carlo simulation. The novelty of our technique is that it can be used for slow crystallization processes, while the simple following of trajectories can be applied only for fast reactions. Our method is a possibility for determination of elementary rate constants of crystal growth that seems to be necessary for the long-time goal of computer-aided crystal design.

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