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 Physics Faculty Publications and Presentations (7)
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Articles 1  30 of 30
FullText Articles in Physics
Computational Studies Of Thermal Properties And Desalination Performance Of LowDimensional Materials, Yang Hong
Student Research Projects, Dissertations, and Theses  Chemistry Department
During the last 30 years, microelectronic devices have been continuously designed and developed with smaller size and yet more functionalities. Today, hundreds of millions of transistors and complementary metaloxidesemiconductor cells can be designed and integrated on a single microchip through 3D packaging and chip stacking technology. A large amount of heat will be generated in a limited space during the operation of microchips. Moreover, there is a high possibility of hot spots due to nonuniform integrated circuit design patterns as some core parts of a microchip work harder than other memory parts. This issue becomes acute as stacked microchips get ...
RealTime Observation Of Molecular Spinning With Angular HighHarmonic Spectroscopy, Lixin He, Pengfei Lan, AnhThu Le, Baoning Wang, Bincheng Wang, Xiaosong Zhu, Peixiang Lu, C. D. Lin
RealTime Observation Of Molecular Spinning With Angular HighHarmonic Spectroscopy, Lixin He, Pengfei Lan, AnhThu Le, Baoning Wang, Bincheng Wang, Xiaosong Zhu, Peixiang Lu, C. D. Lin
Physics Faculty Research & Creative Works
We demonstrate an angular highharmonic spectroscopy method to probe the spinning dynamics of a molecular rotation wave packet in real time. With the excitation of two timedelayed, polarizationskewed pump pulses, the molecular ensemble is impulsively kicked to rotate unidirectionally, which is subsequently irradiated by another delayed probe pulse for highorder harmonic generation (HHG). The spatiotemporal evolution of the molecular rotation wave packet is visualized from the timedependent angular distributions of the HHG yields and frequency shift measured at various polarization directions and time delays of the probe pulse. The observed frequency shift in HHG is demonstrated to arise from the ...
Computational Analysis Of Poliovirus Structural Dynamics Using A CoarseGrained Model, Maneesh Koneru
Computational Analysis Of Poliovirus Structural Dynamics Using A CoarseGrained Model, Maneesh Koneru
University Scholar Projects
Though eradicated in most of the world, poliovirus remains a common model virus for a family of mammalian viruses known as Picornaviruses. Despite the development of a vaccination, little is understood about the infection process, particularly the mechanism of cell entry. Experimental studies have attempted to elucidate the dynamics of this process and have proposed pathways focused on VP4, the smallest of the four peptides which makes up the viral capsid, and its interaction with the pentameric interfaces of the five fold axes. This study utilizes coarsegrained molecular dynamics to supplement these proposed mechanisms with simplified simulations which reduce the ...
Implementation Of MetalFriendly Eam/FsType SemiEmpirical Potentials In HoomdBlue: A GpuAccelerated Molecular Dynamics Software, Lin Yang, Feng Zhang, CaiZhuang Wang, KaiMing Ho, Alex Travesset
Implementation Of MetalFriendly Eam/FsType SemiEmpirical Potentials In HoomdBlue: A GpuAccelerated Molecular Dynamics Software, Lin Yang, Feng Zhang, CaiZhuang Wang, KaiMing Ho, Alex Travesset
Ames Laboratory Accepted Manuscripts
We present an implementation of EAM and FS interatomic potentials, which are widely used in simulating metallic systems, in HOOMDblue, a software designed to perform classical molecular dynamics simulations using GPU accelerations. We first discuss the details of our implementation and then report extensive benchmark tests. We demonstrate that singleprecision floating point operations efficiently implemented on GPUs can produce sufficient accuracy when compared against doubleprecision codes, as demonstrated in test simulations of calculations of the glasstransition temperature of Cu64.5Zr35.5, and pair correlation function of liquid Ni3Al. Our code scales well with the size of the simulating system on ...
Phase Transitions And Their Interaction With Dislocations In Silicon, Valery I. Levitas, Hao Chen, Liming Xiong
Phase Transitions And Their Interaction With Dislocations In Silicon, Valery I. Levitas, Hao Chen, Liming Xiong
Aerospace Engineering Publications
In this paper, phase transformations (PTs) in silicon were investigated through molecular dynamics (MD) using Tersoff potential. In the first step, simulations of PTs in single crystal silicon under various stresscontrolled loading were carried out. Results shows that all instability points under various stress states are described by criteria, which are linear in the space of normal stresses. There is a region in the stress space in which conditions for direct and reverse PTs coincide and a unique homogeneous phase transition (without nucleation) can be realized. Finally, phase transition in bicrystalline silicon with a dislocation pileup along the grain boundary ...
Cooling Rate Dependence Of Structural Order In Ni62nb38 Metallic Glass, Tongqi Wen, Yang Sun, Beilin Ye, Ling Tang, Zejin Yang, KaiMing Ho, CaiZhuang Wang, Nan Wang
Cooling Rate Dependence Of Structural Order In Ni62nb38 Metallic Glass, Tongqi Wen, Yang Sun, Beilin Ye, Ling Tang, Zejin Yang, KaiMing Ho, CaiZhuang Wang, Nan Wang
Ames Laboratory Accepted Manuscripts
Molecular dynamics (MD) simulations are performed to study the structure of Ni62Nb38 bulk metallic glass at the atomistic level. Structural analysis based on the cluster alignment method is carried out and a new Nicentered distortedicosahedra (DISICO) motif is excavated. We show that the shortrange order and mediumrange order in the glass are enhanced with lower cooling rate. Almost 50% of the clusters around the Ni atoms in the wellannealed Ni62Nb38 glass sample from our MD simulations can be classified as DISICO. It is revealed that the structural distortion with respect to the perfect icosahedra is driven by chemical ordering in ...
Entropy Production And Volume Contraction In Thermostated Hamiltonian Dynamics, John D. Ramshaw
Entropy Production And Volume Contraction In Thermostated Hamiltonian Dynamics, John D. Ramshaw
Physics Faculty Publications and Presentations
Patra et al. [Int. J. Bifurcat. Chaos 26, 1650089 (2016)] recently showed that the timeaveraged rates of entropy production and phasespace volume contraction are equal for several different molecular dynamics methods used to simulate nonequilibrium steady states in Hamiltonian systems with thermostated temperature gradients. This equality is a plausible statistical analog of the second law of thermodynamics. Here we show that those two rates are identically equal in a wide class of methods in which the thermostat variables z are determined by ordinary differential equations of motion (i.e., methods of the NoséHoover or integral feedback control type). This class ...
Effects Of Schmid Factor And Slip Nucleation On Deformation Mechanism In ColumnarGrained Nanotwinned Ag And Cu, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard Lesar
Effects Of Schmid Factor And Slip Nucleation On Deformation Mechanism In ColumnarGrained Nanotwinned Ag And Cu, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard Lesar
Ames Laboratory Publications
We report the results of a molecular dynamics study of the effect of texture on the yield and peak stresses in columnargrained nanotwinned Ag and Cu. The simulations suggest that in pure nanotwinned facecentered cubic metals, the strength is determined primarily by the cooperation or competition between two major factors: the magnitude of the Schmid factors for the available slip systems and the effectiveness of grain boundaries (and their triplejunctions) in generating dislocations. These factors and their relative impact depend on the geometry of the specimen relative to the applied stress, which is typically reflected in the texture of the ...
Scaling And AlphaHelix Regulation Of Protein Relaxation In A Lipid Bilayer, Liming Qiu, Creighton Buie, Kwan H. Cheng, Mark W. Vaughn
Scaling And AlphaHelix Regulation Of Protein Relaxation In A Lipid Bilayer, Liming Qiu, Creighton Buie, Kwan H. Cheng, Mark W. Vaughn
Physics and Astronomy Faculty Research
Protein conformation and orientation in the lipid membrane plays a key role in many cellular processes. Here we use molecular dynamics simulation to investigate the relaxation and Cterminus diffusion of a model helical peptide: betaamyloid (Aβ) in a lipid membrane.We observed that after the helical peptide was initially halfembedded in the extracelluar leaflet of phosphatidylcholine (PC) or PC/cholesterol (PC/CHOL) membrane, the Cterminus diffused across the membrane and anchored to PC headgroups of the cytofacial lipid leaflet. In some cases, the membrane insertion domain of the Aβ was observed to partially unfold. Applying a sigmoidal fit to the ...
Statistical Mechanical Models For Dissociative Adsorption Of O2 On Metal(100) Surfaces With Blocking, Steering, And Funneling, DaJiang Liu, James W. Evans
Statistical Mechanical Models For Dissociative Adsorption Of O2 On Metal(100) Surfaces With Blocking, Steering, And Funneling, DaJiang Liu, James W. Evans
Physics and Astronomy Publications
We develop statistical mechanical models amenable to analytic treatment for the dissociative adsorption of O2 at hollow sites on fcc(100) metal surfaces. The models incorporate exclusion of nearestneighbor pairs of adsorbed O. However, corresponding simple siteblocking models, where adsorption requires a large ensemble of available sites, exhibit an anomalously fast initial decrease in sticking. Thus, in addition to blocking, our models also incorporate more facile adsorption via orientational steering and funneling dynamics (features supported by ab initio Molecular Dynamics studies). Behavior for equilibrated adlayers is distinct from those with finite adspecies mobility. We focus on the lowtemperature limitedmobility regime ...
Structural Flexibility And Oxygen Diffusion Pathways In Monomeric Fluorescent Proteins, Chola K. Regmi
Structural Flexibility And Oxygen Diffusion Pathways In Monomeric Fluorescent Proteins, Chola K. Regmi
FIU Electronic Theses and Dissertations
Fluorescent proteins are valuable tools as biochemical markers for studying cellular processes. Red fluorescent proteins (RFPs) are highly desirable for in vivo applications because they absorb and emit light in the red region of the spectrum where cellular autofluorescence is low. The naturally occurring fluorescent proteins with emission peaks in this region of the spectrum occur in dimeric or tetrameric forms. The development of mutant monomeric variants of RFPs has resulted in several novel FPs known as mFruits. Though oxygen is required for maturation of the chromophore, it is known that photobleaching of FPs is oxygen sensitive, and oxygenfree conditions ...
Lattice Thermal Conductivity In Bulk And Nanosheet Naxcoo2, Denis Demchenko, David B. Ameen
Lattice Thermal Conductivity In Bulk And Nanosheet Naxcoo2, Denis Demchenko, David B. Ameen
Physics Publications
In this paper we present the results of calculations of the lattice thermal conductivity of layered complex metal oxide Na_{x}CoO_{2} within the Green–Kubo theory. Using Na_{x}CoO_{2} we identify the two competing mechanisms responsible for the favorable scaling properties of the Green–Kubo method for calculating the lattice thermal conductivity. The artificial correlations of the heat flux fluctuations due to the finite size of the supercells are partially cancelled by the missing long wavelength acoustic phonon modes. We compute the lattice thermoelectric properties of bulk Na_{x}CoO_{2} with varying stoichiometry, structural defects ...
Low Mach Number Fluctuating Hydrodynamics Of Diffusively Mixing Fluids, Aleksandar Donev, Andy J. Nonaka, Yifei Sun, Thomas Fai, Alejandro Garcia, John B. Bell
Low Mach Number Fluctuating Hydrodynamics Of Diffusively Mixing Fluids, Aleksandar Donev, Andy J. Nonaka, Yifei Sun, Thomas Fai, Alejandro Garcia, John B. Bell
Faculty Publications
We formulate low Mach number fluctuating hydrodynamic equations appropriate for modeling diffusive mixing in isothermal mixtures of fluids with different density and transport coefficients. These equations eliminate the fast isentropic fluctuations in pressure associated with the propagation of sound waves by replacing the equation of state with a local thermodynamic constraint. We demonstrate that the low Mach number model preserves the spatiotemporal spectrum of the slower diffusive fluctuations. We develop a strictly conservative finitevolume spatial discretization of the low Mach number fluctuating equations in both two and three dimensions. We construct several explicit RungeKutta temporal integrators that strictly maintain the ...
Electric FieldDriven Water Dipoles: Nanoscale Architecture Of Electroporation, Mayya Tokman, Jane Hyojin Lee, Zachary A. Levine, MingChak Ho, Michael E. Colvin, P. Thomas Vernier
Electric FieldDriven Water Dipoles: Nanoscale Architecture Of Electroporation, Mayya Tokman, Jane Hyojin Lee, Zachary A. Levine, MingChak Ho, Michael E. Colvin, P. Thomas Vernier
Bioelectrics Publications
Electroporation is the formation of permeabilizing structures in the cell membrane under the influence of an externally imposed electric field. The resulting increased permeability of the membrane enables a wide range of biological applications, including the delivery of normally excluded substances into cells. While electroporation is used extensively in biology, biotechnology, and medicine, its molecular mechanism is not well understood. This lack of knowledge limits the ability to control and finetune the process. In this article we propose a novel molecular mechanism for the electroporation of a lipid bilayer based on energetics analysis. Using molecular dynamics simulations we demonstrate that ...
Molecular Dynamics Simulations Reveal The Protective Role Of Cholesterol In ΒAmyloid ProteinInduced Membrane Disruptions In Neuronal Membrane Mimics, Liming Qiu, Creighton Buie, Andrew Reay, Mark W. Vaughn, Kwan H. Cheng
Molecular Dynamics Simulations Reveal The Protective Role Of Cholesterol In ΒAmyloid ProteinInduced Membrane Disruptions In Neuronal Membrane Mimics, Liming Qiu, Creighton Buie, Andrew Reay, Mark W. Vaughn, Kwan H. Cheng
Physics and Astronomy Faculty Research
Interactions of βamyloid (Aβ) peptides with neuronal membranes have been associated with the pathogenesis of Alzheimer's disease (AD); however, the molecular details remain unclear. We used atomistic molecular dynamics (MD) simulations to study the interactions of Aβ_{40} and Aβ_{42} with model neuronal membranes. The differences between cholesterolenriched and depleted lipid domains were investigated by the use of model phosphatidylcholine (PC) lipid bilayers with and without 40 mol % cholesterol. A total of 16 independent 200 ns simulation replicates were investigated. The surface area per lipid, bilayer thickness, water permeability barrier, and lipid order parameter, which are sensitive indicators ...
Experimental And Theoretical Investigation Of Molecular Field Effects By PolarizationResolved Resonant Inelastic XRay Scattering, Stephane Carniato, Renaud Guillemin, Wayne C. Stolte, Loic Journel, Richard Taieb, Dennis W. Lindle, Marc Simon
Experimental And Theoretical Investigation Of Molecular Field Effects By PolarizationResolved Resonant Inelastic XRay Scattering, Stephane Carniato, Renaud Guillemin, Wayne C. Stolte, Loic Journel, Richard Taieb, Dennis W. Lindle, Marc Simon
Chemistry and Biochemistry Faculty Publications
We present a combined theoretical and experimental study of molecular field effects on molecular core levels. Polarizationdependent resonant inelastic xray scattering is observed experimentally after resonant Kshell excitation of CF_{3}Cl and HCl. We explain the linear dichroism observed in spinorbit level intensities as due to molecular field effects, including singlettriplet exchange, and interpret this behavior in terms of population differences in the 2p_{x,y,z }innershell orbitals. We investigate theoretically the different factors that can affect the electronic populations and the dynamical R dependence of the spinorbit ratio. Finally, the results obtained are used to interpret the ...
YoungType Interference In (E, 2e) Ionization Of H₂, D. S. MilneBrownlie, Matthew S. Foster, Junfang Gao, B. Lohmann, Don H. Madison
YoungType Interference In (E, 2e) Ionization Of H₂, D. S. MilneBrownlie, Matthew S. Foster, Junfang Gao, B. Lohmann, Don H. Madison
Physics Faculty Research & Creative Works
We have investigated the electron impact single ionization of the hydrogen molecule, with fully determined kinematics. The experimental and theoretical results are compared with He ionization under the same conditions. The results indicate that the ejected electron angular distribution for H_{2} is modified due to Youngtype interference between ionization amplitudes for scattering from the two centers in the hydrogen molecule. The observable result is a suppression of the backward scattering (recoil) peak compared with the binary peak.
Erratum: "Environmental Swap Energy And Role Of Configurational Entropy In Transfer Of Small Molecules From Water Into Alkanes", Pavel Smejtek, Robert Campbell Word
Erratum: "Environmental Swap Energy And Role Of Configurational Entropy In Transfer Of Small Molecules From Water Into Alkanes", Pavel Smejtek, Robert Campbell Word
Physics Faculty Publications and Presentations
Presents correction to an article related to configurational entropy in transfer of small molecules from water into alkanes, published in the 2005 issue of "The Journal Chemical Physics" and is available online at: http://archives.pdx.edu/ds/psu/8364
Growth Coalescence Shapes For Islands During Metal (100) Homoepitaxy, Maozhi Li, James W. Evans
Growth Coalescence Shapes For Islands During Metal (100) Homoepitaxy, Maozhi Li, James W. Evans
Mathematics Publications
During submonolayer homoepitaxy, instability in the shapes of growing twodimensional islands can develop due to the diffusionlimited aggregation of deposited adatoms at their edges. However, in metal (100) systems, periphery diffusion is typically efficient, quenching this shape instability, and resulting in simple nearsquare or nearrectangular shapes of isolated islands. Despite this feature, growth coalescence shapes resulting from collision of two or more growing islands are nontrivial. These coalescence shapes are elucidated here by developing three complementary formulations: (i) suitable atomistic latticegas models analyzed by kinetic Monte Carlo simulation; (ii) deterministic rate equations for the dynamics of kinks along island step ...
Environmental Swap Energy And Role Of Configurational Entropy In Transfer Of Small Molecules From Water Into Alkanes, Pavel Smejtek, Robert Campbell Word
Environmental Swap Energy And Role Of Configurational Entropy In Transfer Of Small Molecules From Water Into Alkanes, Pavel Smejtek, Robert Campbell Word
Physics Faculty Publications and Presentations
We studied the effect of segmented solvent molecules on the free energy of transfer of small molecules from water into alkanes (hexane, heptane, octane, decane, dodecane, tetradecane, and hexadecane). For these alkanes we measured partition coefficients of benzene, 3methylindole (3MI), 2,3,4,6tetrachlorophenol (TeCP), and 2,4,6tribromophenol (TriBP) at 3, 11, 20, 3, and 47 °C. For 3MI, TeCP, and TriBP the dependence of free energy of transfer on length of alkane chains was found to be very different from that for benzene. In contrast to benzene, the energy of transfer for 3MI, TeCP, and TriBP was independent ...
Temperature Dependence Of Droplet Nucleation In A Yukawa Fluid, Jinsong Li, Gerald Wilemski
Temperature Dependence Of Droplet Nucleation In A Yukawa Fluid, Jinsong Li, Gerald Wilemski
Physics Faculty Research & Creative Works
We have studied the temperature dependence of gastoliquid nucleation in Yukawa fluids with gradient theory and density functional theory. Each of these nonclassical theories exhibits a weaker (i.e., better) temperature dependence than classical nucleation theory. At fixed temperature, the reversible work to form a critical nucleus found from gradient theory approaches the value given by density functional theory as the supersaturation increases. At high temperatures, the two theories remain quite close over a wide range of vapor densities. As the temperature is reduced, the difference between the two theories increases with decreasing vapor density. Compared to the classical theory ...
Influence Of Sample Shape On The Production Of Intrinsic Localized Modes In An Antiferromagnetic Lattice, M. Sato, Lars Q. English, B. E. Hubbard, A. J. Sievers
Influence Of Sample Shape On The Production Of Intrinsic Localized Modes In An Antiferromagnetic Lattice, M. Sato, Lars Q. English, B. E. Hubbard, A. J. Sievers
Faculty and Staff Publications By Year
The formation of intrinsic localized modes (ILMs) via the uniform mode instability is considered for different crystal geometries for a layered quasi1D antiferromagnet (C_{2} H_{5} NH_{3 })_{2} CuCl_{4}. By varying the sample shape and hence the demagnetization factor, it is possible to tune the frequency of the uniform mode with respect to the longwavelength spin wave frequencies. Molecular dynamics simulations predict that the smaller the difference between the two frequencies, the easier to create ILMs from the large amplitude uniform mode. High power nonlinear experiments on samples of different shapes confirm this prediction.
Local Versus Nonlocal OrderParameter Field Theories For Quantum Phase Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta
Local Versus Nonlocal OrderParameter Field Theories For Quantum Phase Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta
Physics Faculty Research & Creative Works
General conditions are formulated that allow us to determine which quantum phase transitions in itinerant electron systems can be described by a local LandauGinzburgWilson (LGW) theory solely in terms of the order parameter. A crucial question is the degree to which the order parameter fluctuations couple to other soft modes. Three general classes of zerowavenumber order parameters, in the particlehole spinsinglet and spintriplet channels and in the particleparticle channel, respectively, are considered. It is shown that the particlehole spinsinglet class does allow for a local LGW theory, while the other two classes do not. The implications of this result for ...
ShortPulse LaserInduced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story
ShortPulse LaserInduced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story
Physics Faculty Research & Creative Works
Atoms in doubly excited states above the first ionization limit can decay via autoionization in which an electron is emitted leaving an ion, or by photoemission which leaves the atom in a singly excited state. In this paper, it is demonstrated that interaction between the atoms and a laser pulse that is short compared to the autoionization lifetime can lead to large enhancement of the photoemission process by stimulating the atoms to emit a photon. Since the resultant singly excited atoms do not autoionize, this process can be viewed as an enhancement of the stabilization of the doubly excited atoms ...
Decay Of Molecules At Spherical Surfaces: Nonlocal Effects, P.T. Leung
Decay Of Molecules At Spherical Surfaces: Nonlocal Effects, P.T. Leung
Physics Faculty Publications and Presentations
The decay rates for molecules in the vicinity of a metallic sphere are investigated in a phenomenological approach for very close moleculesurface distances d. The FuchsClaro model [Phys. Rev. B 35, 3722 (1987)] is adopted to describe the polarizability of the sphere with the nonlocal dielectric response being accounted for within the hydrodynamic description. The results show significant differences when compared with those obtained previously within a local description for dlsim50 Aring, with extra resonances observed in the highfrequency regime, a phenomenon similar to that noted previously by Ruppin (1982), in his calculation of the extinction cross section for such ...
The Spectroscopy And Molecular Dynamics Of The High Frequency Ν1 6 Intermolecular Vibrations In Hcn‐‐‐Hf And Dcn‐‐‐Df, B. A. Wofford, M. W. Jackson, Shannon Lieb, J. W. Bevan
The Spectroscopy And Molecular Dynamics Of The High Frequency Ν1 6 Intermolecular Vibrations In Hcn‐‐‐Hf And Dcn‐‐‐Df, B. A. Wofford, M. W. Jackson, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work  LAS
Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν^{0} _{6} [ν_{0}=1132.4783(2) cm^{−} ^{1}] in HCN‐‐‐HF and its corresponding perdeuterated fundamental ν^{1} _{6} [ν_{0}=409.1660(2) cm^{−} ^{1}] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K _{6} _{6}=537(17) and K _{6} _{6} _{6} _{6}=4.98(12) cm^{−} ^{1} which in turn are used to estimate the pertinent cubic band ...
EnergyTransfer Theory For The Classical Decay Rates Of Molecules At Rough Metallic Surfaces, P.T. Leung, Thomas F. George
EnergyTransfer Theory For The Classical Decay Rates Of Molecules At Rough Metallic Surfaces, P.T. Leung, Thomas F. George
Physics Faculty Publications and Presentations
The problem of the decay rates for molecules at rough metallic surfaces is considered, where the classical electromagnetic energytransfer theory of Chance, Prock, and Silbey for a flat surface is generalized to the case of a rough boundary. A dynamical theory is constructed through the combination of the Sommerfeld antenna theory and the integral equation formalism of Maxwell's equations at rough boundaries established mainly by Maradudin, Mills, and Agarwal. Perturbative solutions are obtained and numerical results are given with reference to a shallow sinusoidal grating surface. The results, when compared with those obtained previously from the application of the ...
Molecular Dynamics In Hydrogen‐Bonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field For Hcn‐‐‐Hf, B. A. Wofford, Shannon Lieb, J. W. Bevan
Molecular Dynamics In Hydrogen‐Bonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field For Hcn‐‐‐Hf, B. A. Wofford, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work  LAS
Observation of the 2ν_{1} overtone band in the hydrogen‐bonded complex HCN‐‐‐HF permits evaluation of the anharmonicity constant X _{1} _{1}=−116.9(1) cm^{−} ^{1} and determination of the anharmonicity corrected fundamental frequency ω_{1}. This information, and available data from previous rovibrational analyses in the common and perdeuterated isotopic species of HCN‐‐‐HF, offer an opportunity for calculation of an approximate stretching harmonic force field. With the assumptions f _{1} _{2}=f _{2} _{4}=0.0, the remaining force constants (in mdyn/Å) are evaluated as: f _{1} _{1}=8.600(20), f _{2} _{2}=6 ...
An Approximate Variational Method For Improved Thermodynamics Of Molecular Fluids, M. S. Shaw, J. D. Johnson, John D. Ramshaw
An Approximate Variational Method For Improved Thermodynamics Of Molecular Fluids, M. S. Shaw, J. D. Johnson, John D. Ramshaw
Physics Faculty Publications and Presentations
For a certain class of thermodynamic perturbation theories, a generalization of the GibbsBogoliubov inequality holds through second order of perturbation theory and for a subset of terms the inequality is true to infinite order. Using this approximate variational principle, a perturbation theory is chosen for which the Helmholtz free energy of the reference system is minimized under the constraint that the first order term is identically zero. We apply these ideas to the determination of effective spherical potentials that accurately reproduce the thermodynamics of nonspherical molecular potentials. For a diatomicLennardJones (DLJ) potential with l ∕σ = 0.793, the resulting spherical ...
Brownian Motion In A Flowing Fluid, John D. Ramshaw
Brownian Motion In A Flowing Fluid, John D. Ramshaw
Physics Faculty Publications and Presentations
A phenomenological theory is developed for Brownian motion in a flowing incompressible fluid. The Brownian particles are regarded as an ideal gas subject to a position and timedependent force field that represents interactions with the host fluid. This approach immediately leads to deterministic partial differential equations of motion for the Brownian particles. These equations are then examined in the limit of large friction, in which they imply an expression for the diffusional mass flux of Brownian particles. This expression is a sum of terms representing concentration, forced, thermal, and pressure diffusion. Comparisons are made with earlier work, and with the ...