577 research outputs found
Multiple magneto-phonon resonances in graphene
Our low-temperature magneto-Raman scattering measurements performed on
graphene-like locations on the surface of bulk graphite reveal a new series of
magneto-phonon resonances involving both K-point and Gamma-point phonons. In
particular, we observe for the first time the resonant splitting of three
crossing excitation branches. We give a detailed theoretical analysis of these
new resonances. Our results highlight the role of combined excitations and the
importance of multi-phonon processes (from both K and Gamma points) for the
relaxation of hot carriers in graphene.Comment: 20 pages, 11 figure
Using the fractional interaction law to model the impact dynamics in arbitrary form of multiparticle collisions
Using the molecular dynamics method, we examine a discrete deterministic
model for the motion of spherical particles in three-dimensional space. The
model takes into account multiparticle collisions in arbitrary forms. Using
fractional calculus we proposed an expression for the repulsive force, which is
the so called fractional interaction law. We then illustrate and discuss how to
control (correlate) the energy dissipation and the collisional time for an
individual article within multiparticle collisions. In the multiparticle
collisions we included the friction mechanism needed for the transition from
coupled torsion-sliding friction through rolling friction to static friction.
Analysing simple simulations we found that in the strong repulsive state binary
collisions dominate. However, within multiparticle collisions weak repulsion is
observed to be much stronger. The presented numerical results can be used to
realistically model the impact dynamics of an individual particle in a group of
colliding particles.Comment: 17 pages, 8 figures, 1 table; In review process of Physical Review
An ab initio and matrix isolation infrared study of the 1:1 C<SUB>2</SUB>H<SUB>2</SUB>-CHCl<SUB>3</SUB> adduct
The details of weak C-H···π interactions that control several inter and intramolecular structures have been studied experimentally and theoretically for the 1:1 C2H2-CHCl3 adduct. The adduct was generated by depositing acetylene and chloroform in an argon matrix and a 1:1 complex of these species was identified using infrared spectroscopy. Formation of the adduct was evidenced by shifts in the vibrational frequencies compared to C2H2 and CHCl3 species. The molecular structure, vibrational frequencies and stabilization energies of the complex were predicted at the MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels. Both the computational and experimental data indicate that the C2H2-CHCl3 complex has a weak hydrogen bond involving a C-H···π interaction, where the C2H2 acts as a proton acceptor and the CHCl3 as the proton donor. In addition, there also appears to be a secondary interaction between one of the chlorine atoms of CHCl3 and a hydrogen in C2H2. The combination of the C-H···π interaction and the secondary Cl···H interaction determines the structure and the energetics of the C2H2-CHCl3 complex. In addition to the vibrational assignments for the C2H2-CHCl3 complex we have also observed and assigned features owing to the proton accepting C2H2 submolecule in the acetylene dimer
Project #82: HFWH Vertical Treatment Zone
Problem Statement: Limited Emergency Department bed capacity and increased acuity resulted in increased left without completing service (LWCS) resulting in increased patient safety risk.
Goal: Design a new patient throughput workflow to provide safe, timely and quality patient-centered care resulting in decreased LWSC, decreased arrival to provider times, decreased LOS of the discharged patient, and increased patient satisfaction.https://scholarlycommons.henryford.com/qualityexpo2023/1007/thumbnail.jp
Accurate calculation of polarization-related quantities in semiconductors
We demonstrate that polarization-related quantities in semiconductors can be
predicted accurately from first-principles calculations using the appropriate
approach to the problem, the Berry-phase polarization theory. For III-V
nitrides, our test case, we find polarizations, polarization differences
between nitride pairs, and piezoelectric constants quite close to their
previously established values. Refined data are nevertheless provided for all
the relevant quantities.Comment: RevTeX 4 pages, no figure
Electrical switch to the resonant magneto-phonon effect in graphene
We report a comprehensive study of the tuning with electric fields of the
resonant magneto-exciton optical phonon coupling in gated graphene. For
magnetic fields around T which correspond to the range of the
fundamental magneto-phonon resonance, the electron-phonon coupling can be
switched on and off by tuning the position of the Fermi level in order to Pauli
block the two fundamental inter Landau level excitations. The effects of such a
profound change in the electronic excitation spectrum are traced through
investigations of the optical phonon response in polarization resolved
magneto-Raman scattering experiments. We report on the observation of a
splitting of the phonon feature with satellite peaks developing, at particular
values of the Landau level filling factor, on the low or on the high energy
side of the phonon, depending on the relative energy of the discrete electronic
excitation and of the optical phonon. Shifts of the phonon energy as large as
cm are observed close to the resonance. The intraband electronic
excitation, the cyclotron resonance, is shown to play a relevant role in the
observed spectral evolution of the phonon response.Comment: 5 Figure
First-principles prediction of structure, energetics, formation enthalpy, elastic constants, polarization, and piezoelectric constants of AlN, GaN, and InN: comparison of local and gradient-corrected density-functional theory
A number of diverse bulk properties of the zincblende and wurtzite III-V
nitrides AlN, GaN, and InN, are predicted from first principles within density
functional theory using the plane-wave ultrasoft pseudopotential method, within
both the LDA (local density) and GGA (generalized gradient) approximations to
the exchange-correlation functional. Besides structure and cohesion, we study
formation enthalpies (a key ingredient in predicting defect solubilities and
surface stability), spontaneous polarizations and piezoelectric constants
(central parameters for nanostructure modeling), and elastic constants. Our
study bears out the relative merits of the two density functional approaches in
describing diverse properties of the III-V nitrides (and of the parent species
N, Al, Ga, and In), and leads us to conclude that the GGA approximation,
associated with high-accuracy techniques such as multiprojector ultrasoft
pseudopotentials or modern all-electron methods, is to be preferred in the
study of III-V nitrides.Comment: RevTeX 6 pages, 12 tables, 0 figure
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