94,594 research outputs found
First-principles calculations of a high-pressure synthesized compound PtC
First-principles density-functional method is used to study the recently
high-pressure synthesized compound PtC. It is confirmed by our calculations
that the platinum carbide has a zinc-blende ground-state phase at zero pressure
and the rock-salt structure is a high-pressure phase. The theoretical
transition pressure from zinc-blende to rock-salt is determined to be 52GPa.
Furthermore, our calculation shows the possibility that the experimentally
synthesized PtC by Ono et al. under high pressure condition might undergo a
transition from rock-salt structure to zinc-blende after the pressure quench to
ambient condition.Comment: A revised versio
Volumetric pattern analysis of airborne antennas
By blending together the roll and elevation plane high frequency solutions, a very efficient technique was developed for the volumetric pattern analysis of antennas mounted on the fuselage of a generalized aircraft. The fuselage is simulated by an infinitely long, perfectly conducting, elliptic cylinder in cross-section and a composite elliptic cylinder in profile. The wings, nose section, stabilizers, and landing gear doors may be modeled by finite flat or bent plates. Good agreement with accurate scale model measurements was obtained for a variety of airborne antenna problems
High-Pressure Induced Structural Phase Transition in CaCrO4: Evidence from Raman Scattering Studies
Raman spectroscopic studies have been carried out on CaCrO4 under pressure up
to 26GPa at ambient temperature. The Raman spectra showed CaCrO4 experienced a
continuous structural phase transition started at near 6GPa, and finished at
about 10GPa. It is found that the high-pressure phase could be quenched to
ambient conditions. Pressure dependence of the Raman peaks suggested there
existed four pressure regions related to different structural characters. We
discussed these characters and inferred that the nonreversible structural
transition in CaCrO4, most likely was from a zircon-type (I41/amd) ambient
phase to a scheelite-type high pressure structure (I41/a).Comment: submitte
Strategy for designing broadband epsilon-near-zero metamaterial with loss compensation by gain media
A strategy is proposed to design the broadband gain-doped epsilon-near-zero
(GENZ) metamaterial. Based on the Milton representation of effective
permittivity, the strategy starts in a dimensionless spectral space, where the
effective permittivity of GENZ metamaterial is simply determined by a pole-zero
structure corresponding to the operating frequency range. The physical
structure of GENZ metamaterial is retrieved from the pole-zero structure via a
tractable inverse problem. The strategy is of great advantage in practical
applications and also theoretically reveals the cancellation mechanism
dominating the broadband near-zero permittivity phenomenon in the spectral
space
Donor Electron Wave Functions for Phosphorus in Silicon: Beyond Effective Mass Theory
We calculate the electronic wave-function for a phosphorus donor in silicon
by numerical diagonalisation of the donor Hamiltonian in the basis of the pure
crystal Bloch functions. The Hamiltonian is calculated at discrete points
localised around the conduction band minima in the reciprocal lattice space.
Such a technique goes beyond the approximations inherent in the effective-mass
theory, and can be modified to include the effects of altered donor impurity
potentials, externally applied electro-static potentials, as well as the
effects of lattice strain. Modification of the donor impurity potential allows
the experimentally known low-lying energy spectrum to be reproduced with good
agreement, as well as the calculation of the donor wavefunction, which can then
be used to calculate parameters important to quantum computing applications.Comment: 10 pages, 5 figure
Observation of ferromagnetic resonance in strontium ruthenate (SrRuO3)
We report the observation of ferromagnetic resonance (FMR) in SrRuO3 using
the time-resolved magneto-optical Kerr effect. The FMR oscillations in the
time-domain appear in response to a sudden, optically induced change in the
direction of easy-axis anistropy. The high FMR frequency, 250 GHz, and large
Gilbert damping parameter, alpha ~ 1, are consistent with strong spin-orbit
coupling. We find that the parameters associated with the magnetization
dynamics, including alpha, have a non-monotonic temperature dependence,
suggestive of a link to the anomalous Hall effect.Comment: submitted to Phys. Rev. Let
Fluctuation-dissipation considerations and damping models for ferromagnetic materials
The role of fluctuation-dissipation relations (theorems) for the
magnetization dynamics with Landau-Lifshitz-Gilbert and Bloch-Bloembergen
damping terms are discussed. We demonstrate that the use of the Callen-Welton
fluctuation-dissipation theorem that was proven for Hamiltonian systems can
give an inconsistent result for magnetic systems with dissipation
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