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Articles 1 - 17 of 17

Full-Text Articles in Physics

Quantum Monte Carlo Calculations Applied To Magnetic Molecules , Larry Paul Engelhardt Jan 2006

Quantum Monte Carlo Calculations Applied To Magnetic Molecules , Larry Paul Engelhardt

Retrospective Theses and Dissertations

In this dissertation, we have implemented a quantum Monte Carlo (QMC) algorithm, and have used it to perform calculations for a variety of finite Heisenberg spin systems. A detailed description of the QMC method has been provided, which is followed by applications of the method to various systems. These applications begin with a detailed analysis of the (calculated) equilibrium magnetization and magnetic susceptibility for a number of Heisenberg Hamiltonians. In particular, we have studied the dependence of these quantities on intrinsic spin s, and have quantified the approach to the classical (s → infinity) limit. These results are not specific to ...


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 ...


Physicochemical Properties Of The Anion-Modified Surfaces Of Silver Nanostructures , Morgan Scot Sibbald Jan 1997

Physicochemical Properties Of The Anion-Modified Surfaces Of Silver Nanostructures , Morgan Scot Sibbald

Retrospective Theses and Dissertations

Nano-sized structures of silver were prepared, characterized, and then chemically-modified with the adsorption of molecules and ions on the metal surface. Nanostructures prepared as aqueous colloids were found to have highly regular polyhedral shapes by transmission electron microscopy. Electron diffraction techniques indicated that isolated Ag structures were composed of a single crystalline phase or were multiply-twinned, both having a lattice constant of 4.05 A;Adsorption of iodide and bromide ions on the silver surface was monitored by surface-enhanced Raman spectroscopy. A characteristic halide-metal stretching vibration was observed at 112 cm-1 for I- and at 156 cm-1 for Br-. Extinction ...


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 ...


Nmr And Nqr Study Of The Thermodynamically Stable Quasicrystals , Ananda Shastri Jan 1994

Nmr And Nqr Study Of The Thermodynamically Stable Quasicrystals , Ananda Shastri

Retrospective Theses and Dissertations

[superscript]27Al and [superscript]63,65Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, [superscript]27Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was ...


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 ...


Characterization Of Self-Assembled Carboxylate Monolayers And Multilayers At Copper And Silver , Earl Laird Smith Jan 1992

Characterization Of Self-Assembled Carboxylate Monolayers And Multilayers At Copper And Silver , Earl Laird Smith

Retrospective Theses and Dissertations

A variety of chemically modified surfaces were constructed by the self-assembly method via chemisorption onto evaporated metal films. Monolayer films, self-assembled from solution, include n-alkanoic acids, CH[subscript]3(CH[subscript]2)[subscript] nCOOH, and n-perfluoroalkanoic acids, CF[subscript]3(CF[subscript]2)[subscript] nCOOH, on copper, and n-alkanethiolates, CH[subscript]3(CH[subscript]2)[subscript] nSH on copper. Monolayer films were obtained from the gas phase, a newly developed technique, for n-alkanoic acids on silver, and n-alkanethiolates on silver and gold. Multilayer films obtained by self-assembly from the gas phase include n-alkanoic acids at copper and silver and perfluoroacids ...


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 ...


Solid State Chemistry Of Some Polar Intermetallic Tetrelides Of The Rare-Earth And Alkaline-Earth Metals , Arnold Mejia Guloy Jan 1992

Solid State Chemistry Of Some Polar Intermetallic Tetrelides Of The Rare-Earth And Alkaline-Earth Metals , Arnold Mejia Guloy

Retrospective Theses and Dissertations

Syntheses of both binary M[subscript]5X[subscript]3 hosts and M[subscript]5X[subscript]3Z interstitial compounds with the same Mn[subscript]5Si[subscript]3 structure type was extended to rare-earth metal tetrelides. The variety of interstitials Z that were incorporated into these host binaries allowed the modulation of the bonding and properties of the host compound without greatly altering or breaking up the structure. Investigations on the binaries also revealed that both La[subscript]5Ge[subscript]3 and La[subscript]5Pb[subscript]3 exist in the Mn[subscript]5Si[subscript]3-type, and La[subscript]5Sn[subscript]3 exists ...


Hydrogen Diffusion And Microstructure In Undoped And Boron-Doped Hydrogenated Amorphous Silicon: An Ir And Sims Study , Saibal Mitra Jan 1991

Hydrogen Diffusion And Microstructure In Undoped And Boron-Doped Hydrogenated Amorphous Silicon: An Ir And Sims Study , Saibal Mitra

Retrospective Theses and Dissertations

Hydrogenated amorphous silicon (a-Si:H) prepared by rf sputtering of a polycrystalline Si target at various rf powers 50 ≤ P ≤ 550 W (0.27-2.97 W/cm[superscript]2), target to substrate distance 1 ≤ d ≤ 2[superscript]'', and varying hydrogen partial pressures. Doping was accomplished by introducing diborane (B[subscript]2H[subscript]6) in the plasma. Hydrogen diffusion was studied from the depth profiles obtained from the SIMS on multilayered a-Si:H/a-Si:(H,D)/a-Si:H samples;The properties of the samples were characterized by IR absorption, optical gap measurements and ESR. IR yielded quantitative and qualitative information total ...


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.


The Radioactive Decay Of 190re And Isomer Ratio Measurements In Photonuclear Reactions , Peter Eugene Haustein Jan 1970

The Radioactive Decay Of 190re And Isomer Ratio Measurements In Photonuclear Reactions , Peter Eugene Haustein

Retrospective Theses and Dissertations

No abstract provided.


The Ferromagnetic Properties Of The Rare Earth Metals , James F. Elliott Jan 1953

The Ferromagnetic Properties Of The Rare Earth Metals , James F. Elliott

Retrospective Theses and Dissertations

No abstract provided.