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>

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>

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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