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Full-Text Articles in Physics

Discontinuous Non-Equilibrium Phase Transition In A Threshold Schloegl Model For Autocatalysis: Generic Two-Phase Coexistence And Metastability, Chi-Jen Wang, Da-Jiang Liu, James W. Evans Apr 2015

Discontinuous Non-Equilibrium Phase Transition In A Threshold Schloegl Model For Autocatalysis: Generic Two-Phase Coexistence And Metastability, Chi-Jen Wang, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

Threshold versions of Schloegl's model on a lattice, which involve autocatalytic creation and spontaneous annihilation of particles, can provide a simple prototype for discontinuous non-equilibrium phase transitions. These models are equivalent to so-called threshold contact processes. A discontinuous transition between populated and vacuum states can occur selecting a threshold of N ≥ 2 for the minimum number, N, of neighboring particles enabling autocatalytic creation at an empty site. Fundamental open questions remain given the lack of a thermodynamic framework for analysis. For a square lattice with N = 2, we show that phase coexistence occurs not at a unique value but ...


Importance And Reliability Of Small Basis Set Ccsd(T) Corrections To Mp2 Binding And Relative Energies Of Water Clusters, Berhane Temelso, Carla Renner, George Shields Mar 2015

Importance And Reliability Of Small Basis Set Ccsd(T) Corrections To Mp2 Binding And Relative Energies Of Water Clusters, Berhane Temelso, Carla Renner, George Shields

Berhane Temelso

MP2 describes hydrogen-bonded systems well, yet a higher-order electron correlation correction in the form of a CCSD(T) calculation is usually necessary to achieve benchmark quality energies. We evaluated the importance and reliability of small basis set CCSD(T) corrections to MP2(δCCSD(T)) both on the binding (ΔE) and relative (ΔΔE) MP2 energies for a large number of systems including four water dimer stationary points and 57 other clusters up to undecamers, (H2O)11. By comparing the MP2 energies with CCSD(T) and the explicitly correlated MP2-F12 energies with variants of CCSD(T)-F12 using different basis sets, we ...


Theoretical Studies Of The Nucleation And Growth Of Thin Metal Films: A Focus On Ag Deposited On Ag(100) , Kyle John Caspersen Jan 2001

Theoretical Studies Of The Nucleation And Growth Of Thin Metal Films: A Focus On Ag Deposited On Ag(100) , Kyle John Caspersen

Retrospective Theses and Dissertations

Theoretical studies of the nucleation and growth of metal films are performed, where the focus is the Molecular Beam Epitaxial (MBE) growth of Ag on the Ag(100) surface. Ag films grown under MBE, for the temperatures and atomic fluxes considered here (0→300K), are very far from equilibrium structures, due to the breaking of detailed balance during deposition. Included are studies of: metal film growth at very low temperatures; the temperature dependence of "mound" formation; the temperature dependence of kinetic roughening; the effect of the step-edge barrier on very thin films, and the post-deposition time dependence of nucleation. For ...


Scanning Tunneling Microscopy Studies Of Submonolayer And Multilayer Ag Films Deposited On Ag(100) , Conrad Robert Stoldt Jan 1999

Scanning Tunneling Microscopy Studies Of Submonolayer And Multilayer Ag Films Deposited On Ag(100) , Conrad Robert Stoldt

Retrospective Theses and Dissertations

A comprehensive analysis of submonolayer and multilayer Ag films deposited on Ag(100) is performed. Extensive ultra-high vacuum Scanning Tunneling Microscopy (STM) experiments are presented revealing exotic equilibration pathways in the Ag adlayer, as well as novel growth modes in multilayer Ag films;Real-time STM imaging of adlayer dynamics at 295 K allows for the elucidation and quantification of various kinetic processes controlling the coarsening of two-dimensional (2D) submonolayer island distributions. Coarsening kinetics are analyzed using a mean-field Smoluchowski rate equation, which gives both a strongly size dependent island diffusion coefficient and an estimate of the size scaling exponent. Details ...


Temperature Dependent Linear And Non-Linear Optical Spectroscopy For Condensed Phase Systems , Mohamad Toutounji Jan 1998

Temperature Dependent Linear And Non-Linear Optical Spectroscopy For Condensed Phase Systems , Mohamad Toutounji

Retrospective Theses and Dissertations

An approximate excited state vibrational Hamiltonian, He, which accounts for both linear and diagonal quadratic electron-phonon coupling is derived and shown to be adequate for mode frequency changes up to ~30%. The associated linear response function which is valid for finite temperature in the absence of damping is obtained. 2-point correlation function or, equivalently, the line broadening function, g(t;T), that provides a good physical description of pure electronic dephasing and vibrational damping for linearly coupled modes is postulated. A linear response function that accounts for pure electronic dephasing and damping for systems with either linearly or quadratically coupled ...


Molecular Dynamics Simulations Of Multiple-Layer Thin Film Growth On Fcc(001) Metal Surfaces , Cynthia Lynne Kelchner Jan 1996

Molecular Dynamics Simulations Of Multiple-Layer Thin Film Growth On Fcc(001) Metal Surfaces , Cynthia Lynne Kelchner

Retrospective Theses and Dissertations

Molecular dynamics simulations are a valuable tool for understanding thin film growth since individual deposition events and atomic growth mechanisms cannot be studied with current experimental techniques. In this dissertation, multiple-layer homoepitaxial thin film growth is studied in detail using reliable interatomic potentials for fcc metals from corrected effective medium theory. The development of these potentials from experimental data on the bulk and on the diatomic molecule is described;Two features are observed to be important during the growth of 50-layer thin films by deposition of single atoms of Pd on Pd(001) and Cu on Cu(001) at 80 ...


Density Functional Studies: First Principles And Semi-Empirical Calculations Of Clusters And Surfaces , Susan Buthaina Sinnott Jan 1993

Density Functional Studies: First Principles And Semi-Empirical Calculations Of Clusters And Surfaces , Susan Buthaina Sinnott

Retrospective Theses and Dissertations

In the research presented here, various theoretical electronic structure techniques are utilized to analyze widely different systems from silicon clusters to transition metal solids and surfaces. For the silicon clusters, first principles density functional methods are used to investigate Si[subscript] N for N = 2-8. The goal is to understand the different types of bonding that can occur in such small clusters where the coordination of the atoms differs substantially from that of the stable bulk tetrahedral bonding. Such uncoordinated structures can provide a good test of more approximate theories that can be used eventually to model silicon surfaces, of ...


The Global Potential Energy Surfaces Of The Lowest Two 1a' States Of The Ozone Molecule: Theoretical Determination And Analysis , Gregory John Atchity Jan 1992

The Global Potential Energy Surfaces Of The Lowest Two 1a' States Of The Ozone Molecule: Theoretical Determination And Analysis , Gregory John Atchity

Retrospective Theses and Dissertations

The two lowest 1A[superscript]' potential energy surfaces (PES) of the ozone molecule are determined and analyzed using accurate ab-initio MCSCF calculations;As appropriate internal coordinates, the shape-scale perimetric coordinates for triatomic molecules are discussed and further developed;Because the previously determined intersection between these two surfaces of like symmetry is unusual, much of the present work involves this intersection. The relevant theory of intersections is reviewed, and a method for characterizing intersections according to the topology of the surfaces in their vicinity is developed;Furthermore, the reasons for this particular crossing in ozone are investigated. The analysis is based ...


Epitaxy Of Metal Atoms On Metal Surfaces: Deposition And Diffusion , David Edward Sanders Jan 1991

Epitaxy Of Metal Atoms On Metal Surfaces: Deposition And Diffusion , David Edward Sanders

Retrospective Theses and Dissertations

The dynamics of epitaxial growth of metal films on FCC(001) metal substrates are investigated in this dissertation. This work focuses on understanding the details of two elementary steps of film growth. First, single metal atom deposition on FCC(001) metal substrates of the same atom type are investigated. The molecular dynamics (MD) method is used to determine the extent of ballistic or transient mobility of the adsorbing atom in the Ni, Cu, Rh, Pd, Ag, Pt, and Au systems. The general lack of ballistic adatom motion in these systems is explained in terms of an efficient transfer of energy ...


Topics In Theoretical Surface Science: I Structures Of Clean And Adsorbate Covered Surfaces Ii Epitaxy Of Metals On Metal Surfaces , Todd Joseph Raeker Jan 1990

Topics In Theoretical Surface Science: I Structures Of Clean And Adsorbate Covered Surfaces Ii Epitaxy Of Metals On Metal Surfaces , Todd Joseph Raeker

Retrospective Theses and Dissertations

The energetics and structures of clean and adsorbate covered surfaces are investigated in this dissertation. First, the formalism, within the Corrected Effective Medium (CEM) method, for calculating the surface energy of a clean surface is derived. The surface energies for many different metals and their low index surfaces are presented. The minimization of the surface energy is then used to predict the multilayer relaxation of the Al(111), (100), (110), Ni(100), (110) and Fe(100) surfaces. The driving forces behind surface relaxation is then examined within the CEM method;Extensions of the surface CEM formalism to calculate the binding ...


Thermal Diffusion In Polyatomic Gases , Maurice Keith Matzen Jan 1974

Thermal Diffusion In Polyatomic Gases , Maurice Keith Matzen

Retrospective Theses and Dissertations

No abstract provided.