Monte Carlo Simulations of Temperature-programmed and Isothermal Desorption from Single-crystal Surfaces
Author: Stephen John Lombardo
Publisher:
Published: 1990
Total Pages: 642
ISBN-13:
DOWNLOAD EBOOKRead and Download eBook Full
Author: Stephen John Lombardo
Publisher:
Published: 1990
Total Pages: 642
ISBN-13:
DOWNLOAD EBOOKAuthor:
Publisher:
Published: 1990
Total Pages: 316
ISBN-13:
DOWNLOAD EBOOKThe kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H2 on Mo(100); and H2 on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H2 coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H2 coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.
Author: Patricia Jean Rivera
Publisher:
Published: 1991
Total Pages: 176
ISBN-13:
DOWNLOAD EBOOKAuthor:
Publisher:
Published: 1990
Total Pages: 498
ISBN-13:
DOWNLOAD EBOOKAuthor:
Publisher:
Published: 1995
Total Pages: 800
ISBN-13:
DOWNLOAD EBOOKAuthor: Leila Rajabibonab
Publisher:
Published: 2017
Total Pages: 150
ISBN-13:
DOWNLOAD EBOOKThe 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.
Author:
Publisher:
Published: 1994-06
Total Pages: 1370
ISBN-13:
DOWNLOAD EBOOKAuthor: Stefan Schinzer
Publisher:
Published: 2000
Total Pages: 132
ISBN-13: 9783826572388
DOWNLOAD EBOOKAuthor: Ralf Vanselow
Publisher:
Published: 1977
Total Pages: 554
ISBN-13:
DOWNLOAD EBOOK