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 Intermolecular interactions (4)
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Articles 1  16 of 16
FullText Articles in Physics
Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough
Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough
Doctoral Dissertations
Diamond films are used at the Spallation Neutron Source (SNS) as the primary charge exchange foils (i.e., stripper foils) of the accelerated 1 GeV (Gigaelectron volts) hydride ions. The most common type of film used is a nanocrystalline diamond film, typically 17 mm x 45 mm (millimeter) with an aerial density of 350 μg/cm^{2} (microgram per square centimeter). The diamond film is deposited on a corrugated silicon substrate using plasmaassisted chemical vapor deposition. After the growth of the diamond film, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon ...
Electronic And Magnetic Materials Under External Stimuli, Kenneth Robert O'Neal
Electronic And Magnetic Materials Under External Stimuli, Kenneth Robert O'Neal
Doctoral Dissertations
The interaction between spin, charge, and lattice degrees of freedom leads to exotic and useful properties in multifunctional materials. This delicate balance of energy scales allows external stimuli such as temperature, magnetic field, or pressure to drive to novel phases. As a local probe technique, spectroscopy can provide insight into the microscopic mechanism of the phase transitions. In this dissertation I present spectroscopic studies of functional materials under extreme conditions.
Nanomaterials have attracted attention because nanoscale confinement affects various material properties and often reduces energy scales or suppress phase transitions. Combining Raman and infrared spectroscopies reveals that the breakdown mechanism ...
Understanding ThreeBody Interactions In Hexagonal Close Packed Solid He4, Ashleigh Locke Barnes
Understanding ThreeBody Interactions In Hexagonal Close Packed Solid He4, Ashleigh Locke Barnes
Doctoral Dissertations
The ground state properties of hexagonal close packed (hcp) solid ^{4}He [He4] are dominated by large atomic zero point motions which make the primary contribution to the solid’s lowtemperature DebyeWaller (DW) factors. Preliminary investigations have also suggested that threebody interactions can play an important role in this system, particularly at higher densities. However, due to their computational cost, these interactions are not generally incorporated into theoretical models of solid ^{4}He [He4]. In order to accurately treat both zero point motion and threebody interactions, we have developed a perturbative treatment in which the threebody energy is added as ...
Investigating The Properties Of Superfluid He4 Through Density Functional Calculations, Matthew Francis Dutra
Investigating The Properties Of Superfluid He4 Through Density Functional Calculations, Matthew Francis Dutra
Doctoral Dissertations
We present a study of isotopically pure He4 systems evaluated using helium density functional theory (HeDFT) with the intent of better understanding their ground state structural and energetic properties, particularly within the scope of singularlydoped helium droplets. We selfconsistently solve for the density profiles and chemical potentials for a wide range of pure helium droplet sizes (up to 9500 atoms) via an imaginary time propagation method, and fit the resultant energetic data to a power law formula to be able to extrapolate values for even larger droplets. Subsequent calculations on singularlydoped droplets within the same size range yield accurate binding ...
Understanding The Plasmonic Properties Of Metallic Nanostructures With Correlated Photon And ElectronDriven Excitations, Vighter Ozezinimize Iberi
Understanding The Plasmonic Properties Of Metallic Nanostructures With Correlated Photon And ElectronDriven Excitations, Vighter Ozezinimize Iberi
Doctoral Dissertations
The collective oscillation of the conduction band electrons in metal nanostructures, known as plasmons, can be used to manipulate light on length scales that are smaller than the diffraction limit of visible light. In this dissertation, a correlated approach is used to probe localized surface plasmon resonances (LSPRs) in metallic nanostructures, and their application to surfaceenhanced spectroscopy. This correlated approach involves the measurement of LSPRs with darkfield optical microscopy (resonanceRayleigh scattering), and electron energyloss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Structural parameters of the exact same nanostructures obtained from the STEM are subsequently used in performing fully ...
MagnetoOptical Properties Of Complex Oxides, Peng Chen
MagnetoOptical Properties Of Complex Oxides, Peng Chen
Doctoral Dissertations
Complex oxides give rise to rich physics and exotic crosscoupled electronic and magnetic properties. This is because of the competing interaction between charge, structure, and magnetism in the materials. In this dissertation I present a spectroscopic investigation of several model complex oxides under external stimuli of magnetic field and temperature. The compounds of interest include BiFeO_{3} [bismuth ferrite] nanoparticles and tetragonal film, Bi_{1x}Nd_{x}FeO_{3 }[neodymium doped bismuth ferrite], αFe_{2}O_{3} [hematite], Ni_{3}V_{2}O_{8 }[nickel vanadate], and RIn_{1x}Mn_{x}O_{3 }[manganese doped rare earth indium oxide ...
Alkane Adsorption On Mgo(100): Volumetric Isotherm, Inelastic Neutron Scattering, And Computational Studies, Andrew Spencer Hicks
Alkane Adsorption On Mgo(100): Volumetric Isotherm, Inelastic Neutron Scattering, And Computational Studies, Andrew Spencer Hicks
Doctoral Dissertations
Volumetric adsorption isotherms and computational molecular dynamics (MD) simulations were performed for nonane and decane adfilms on MgO(100) nanocubes. From the isotherms, variety of thermodynamic quantities are calculated. These values, along with visual inspection of the isotherms, indicate a layer by layer trend from 2D to 3D behavior. This is attributed to the increasing importance of vertical adsorbateadsorbate interactions as distance from the surface increases. Additionally, a 2D phase transition is observed for the first adsorbed layer as indicated by the evolution of the widths of the isotherm first derivative peaks. These experimental results are complemented by the MD ...
Confinement Effects Of Solvation On A Molecule Physisorbed On A Metal Particle, Jacob Fosso Tande
Confinement Effects Of Solvation On A Molecule Physisorbed On A Metal Particle, Jacob Fosso Tande
Doctoral Dissertations
We describe and present results of the implementation of the surface and volume polarization for electrostatics~(SVPE) and the isodensity surface solvation models. Unlike most other implementation of the solvation models where the solute and the solvent are described with multiple numerical representation, our implementation uses a multiresolution, adaptive multiwavelet basis to describe both solute and the solvent. This requires reformulation to use integral equations throughout as well as a conscious management of numerical properties of the basis.
Likewise, we investigate the effects of solvation on the static properties of a molecule physisorbed on a spherical particle, modeled as a ...
Charge, Bonding, And MagnetoElastic Coupling In Nanomaterials, Qi Sun
Charge, Bonding, And MagnetoElastic Coupling In Nanomaterials, Qi Sun
Doctoral Dissertations
Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials because they are intimately connected to charge, structure, and magnetism, and a quantitative analysis of their behavior can reveal microscopic aspects of chemical bonding and spinphonon coupling. To investigate these effects, we measured infrared vibrational properties of bulk and nanoscale MoS_{2} [molybdenum disulfide], MnO [manganese(II) oxide], and CoFe_{2}O_{4} [cobalt iron oxide]. From an analysis of frequencies, oscillator strengths, and highfrequency dielectric constants, we extracted Born and local effective charges, and polarizability for MoS_{2} and MnO. For MoS_{2} nanoparticles ...
Direct Observation Of H_{2} Binding To A Metal Oxide Surface, J. Z. Larese, T. Arnold, L. Frazier, R. J. Hinde, A. J. RamirezCuesta
Direct Observation Of H2 Binding To A Metal Oxide Surface, J. Z. Larese, T. Arnold, L. Frazier, R. J. Hinde, A. J. RamirezCuesta
Chemistry Publications and Other Works
Inelastic neutron scattering is used to probe the dynamical response of H_{2} films adsorbed on MgO(100) as a function of film thickness. Concomitant diffraction measurements and a reduceddimensionality quantum dynamical model provide insight into the moleculesurface interaction potential. At monolayer thickness, the rotational motion is strongly influenced by the surface, so that the molecules behave like quasiplanar rotors. These findings have a direct impact on understanding how molecular hydrogen binds to the surface of materials used in catalytic and storage applications.
A SixDimensional H_{2}–H_{2} Potential Energy Surface For Bound State Spectroscopy, Robert Hinde
A SixDimensional H2–H2 Potential Energy Surface For Bound State Spectroscopy, Robert Hinde
Chemistry Publications and Other Works
We present a sixdimensional potential energy surface for the (H_{2})_{2} dimer based on coupledcluster electronic structure calculations employing large atomcentered Gaussian basis sets and a small set of midbond functions at the dimer’s center of mass. The surface is intended to describe accurately the bound and quasibound states of the dimers (H_{2})_{2}, (D_{2})_{2}, and H_{2}–D_{2} that correlate with H_{2} or D_{2} monomers in the rovibrational levels (v, j) =(0,0), (0,2), (1,0), and (1,2). We employ a closecoupled approach to compute the energies of these ...
InteractionInduced Dipole Moment Of The Ar–H_{2} Dimer: Dependence On The H_{2} Bond Length, Robert J. Hinde
InteractionInduced Dipole Moment Of The Ar–H2 Dimer: Dependence On The H2 Bond Length, Robert J. Hinde
Chemistry Publications and Other Works
We present ab initio calculations of the interactioninduced dipole moment of the Ar–H_{2} van der Waals dimer. The primary focus of our calculations is on the H_{2} bond length dependence of the dipole moment, which determines the intensities of both the collisioninduced H_{2} = 1 ← 0 fundamental band in gaseous Ar–H_{2} mixtures and the dopantinduced H_{2} = 1 ← 0 absorption feature in Ardoped solid H_{2} matrices. Our calculations employ large atomcentered basis sets, diffuse bond functions positioned between the two monomers, and a coupled cluster treatment of valence electron correlation; corevalence correlation effects appear ...
Population Size Bias In DescendantWeighted Diffusion Quantum Monte Carlo Simulations, G. Lee Warren, Robert J. Hinde
Population Size Bias In DescendantWeighted Diffusion Quantum Monte Carlo Simulations, G. Lee Warren, Robert J. Hinde
Chemistry Publications and Other Works
We consider the influence of population size on the accuracy of diffusion quantum Monte Carlo simulations that employ descendant weighting or forward walking techniques to compute expectation values of observables that do not commute with the Hamiltonian. We show that for a simple model system, the ddimensional isotropic harmonic oscillator, the population size must increase rapidly with d in order to ensure that the simulations produce accurate results. When the population size is too small, expectation values computed using descendantweighted diffusion quantum Monte Carlo simulations exhibit significant systematic biases.
Vibrational Dependence Of The H_{2}–H_{2} C_{6} Coefficients, Robert Hinde
Vibrational Dependence Of The H2–H2 C6 Coefficients, Robert Hinde
Chemistry Publications and Other Works
We use the sumoverstates formalism to compute the imaginaryfrequency dipole polarizabilities for H_{2}, as a function of the H–H bond length, at the full configuration interaction level of theory using atomcentered daugccpVQZ basis sets. From these polarizabilities, we obtain isotropic and anisotropic C_{6} dispersion coefficients for a pair of H_{2} molecules as functions of the two molecules’ bond lengths.
InfraredActive Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde
InfraredActive Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde
Chemistry Publications and Other Works
We present a model for the line shapes of infraredactive Q_{1}(0) vibron bands observed in solid parahydrogen doped with low concentrations of spherical substitutional impurities. The line shapes are highly sensitive to the H_{2} vibrational dependence of the dopant–H_{2} interaction. When this vibrational dependence is strong, the dopant can trap the infraredactive vibron in its first solvation shell; in this case, the trapped vibron manifests itself in the absorption spectrum as a narrow feature to the red of the pure solid’s vibron band.
The HeLih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde
The HeLih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde
Chemistry Publications and Other Works
We reconsider the potential energy surface of the He–LiH system recently examined by Gianturco and coworkers [F. A. Gianturco et al., Chem. Phys. 215, 227 (1997)]. We compute the He–LiH interaction energy at the CCSD(T) level using large correlation consistent atomic basis sets supplemented with bond functions. To capture the severe anisotropy of the He–LiH potential, we interpolate our ab initio points in the angular direction with cubic splines, then expand the splines in terms of Legendre polynomials. The resulting smooth potential surface differs substantially from that of Gianturco et al.; in particular, our attractive He ...