Kinetic lattice gas models for adsorption, desorption and diffusion in adsorbates: An investigation using diagonalization methods, Monte Carlo simulations and density functional theory.
Date
2005
Authors
McEwen, Jean-Sabin.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
This thesis consists of several projects which investigate adsorbate systems in or away from equilibrium and the influence of lateral interactions on their measurable properties.
We use the kinetic lattice gas model to study adsorption and desorption processes as well as hopping for a finite, homogeneous one dimensional adsorbate with nearest neighbor interactions and periodic boundary conditions. We solve the complete set of linear ordinary differential equations of motion of all adsorbate correlation functions and obtain their eigenvalues and eigenvectors. We examine the effect of hopping and adsorption processes on the desorption kinetics by calculating the desorption rate, correlation functions and eigenvalues. We generalize the above problem to deal with the time evolution of N particles on Ns sites in a 1-d inhomogeneous adsorbate with hopping processes only. The eigenvalue spectrum is analysed in momentum space from which the diffusion coefficient for the adsorbate is obtained as well as its complete time evolution.
A comprehensive theory of the adsorption of CO on Ru(0001) is then developed to describe the equilibrium properties and the adsorption and desorption kinetics, using a generalization of the theory developed in one dimension to two. The basis is a multi-site kinetic lattice gas model with site exclusion and lateral interactions between CO molecules out to second neighbour unit cells. The theory is such that it reproduces all available experimental data in a consistent manner. Results are compared to an analysis where all relevant site-binding energies and interactions of CO molecules are calculated within density functional theory (DFT).
Equilibrium fluctuations of islands of adsorbed O atoms on Ru(0001) observed with scanning tunneling microscopy (STM) are then analysed. The observed ramified (2x2)-O islands point to complex interactions between the O atoms which are modeled with a lattice gas model and DFT. The DFT calculations show that, in addition to pair-wise attractive interactions between third nearest neighbors, a repulsive three-body interaction exists between these.
Thesis (Ph.D.)--Dalhousie University (Canada), 2005.
We use the kinetic lattice gas model to study adsorption and desorption processes as well as hopping for a finite, homogeneous one dimensional adsorbate with nearest neighbor interactions and periodic boundary conditions. We solve the complete set of linear ordinary differential equations of motion of all adsorbate correlation functions and obtain their eigenvalues and eigenvectors. We examine the effect of hopping and adsorption processes on the desorption kinetics by calculating the desorption rate, correlation functions and eigenvalues. We generalize the above problem to deal with the time evolution of N particles on Ns sites in a 1-d inhomogeneous adsorbate with hopping processes only. The eigenvalue spectrum is analysed in momentum space from which the diffusion coefficient for the adsorbate is obtained as well as its complete time evolution.
A comprehensive theory of the adsorption of CO on Ru(0001) is then developed to describe the equilibrium properties and the adsorption and desorption kinetics, using a generalization of the theory developed in one dimension to two. The basis is a multi-site kinetic lattice gas model with site exclusion and lateral interactions between CO molecules out to second neighbour unit cells. The theory is such that it reproduces all available experimental data in a consistent manner. Results are compared to an analysis where all relevant site-binding energies and interactions of CO molecules are calculated within density functional theory (DFT).
Equilibrium fluctuations of islands of adsorbed O atoms on Ru(0001) observed with scanning tunneling microscopy (STM) are then analysed. The observed ramified (2x2)-O islands point to complex interactions between the O atoms which are modeled with a lattice gas model and DFT. The DFT calculations show that, in addition to pair-wise attractive interactions between third nearest neighbors, a repulsive three-body interaction exists between these.
Thesis (Ph.D.)--Dalhousie University (Canada), 2005.
Keywords
Physics, Condensed Matter.