Materials Literature
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This paper concentrates on a comparison of Al 3p occupied densities of states in crystalline and quasicrystalline Al-Cu-Fe intermetallics. This comparison is made quantitative by computing the two first moments of this partial distribution, which correspond to the partial contribution of Al atoms to the cohesive energ…
We present the results of a computational study of the low-energy dynamics of silica glass. Molecular dynamics simulation results show that parts of the glass structure can undergo large cooperative reorientations of SiO 4 tetrahedra. These motions involve reorientations of about 30 tetrahedra with an energy barrier o…
The structure of liquid sulphur at 400 K, below the polymerization temperature T p = 432 K, is investigated by first-principles molecular-dynamics simulations. The calculated structure factor is in excellent agreement with the experimental data. To investigate the microscopic mechanism of the photo-induced structural…
A transition as a function of increasing temperature from harmonic to anharmonic dynamics has been observed in globular proteins by using spectroscopic, scattering, and computer simulation techniques. We present here results of a dynamic neutron scattering analysis of the solvent dependence of the picosecond-time scal…
A correlation between precise x-ray powder diffraction patterns and atomic size mismatch in disordered mixed crystals (alloys and ionic crystals) is observed. The anisotropy of the elastic moduli has been taken into account for evaluation of the strain energy density of the mixed crystals revealed in x-ray powder diff…
The linear electro-optic (EO) coefficients of Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystals over a broad composition range were investigated at temperatures from −20 to 80 °C. The orientation effect on the EO coefficients was also examined. For crystals poled in the 〈001〉 direction, a large r33 was observed near the morphot…
We have studied structural and luminescence properties of nanostructured (NS-) ZnS:Mn which has potential applications in thin-film electroluminescence (TFEL) devices. As a NS-ZnS:Mn system, a ZnS:Mn/Si3N4 multilayer having thicknesses of 2.5 nm for ZnS and 0.6 nm for Si3N4 was prepared by a conventional rf-magnetron…
C 60 molecules were chemically coupled in the pores of porous Si through a coupling agent and then coated with a layer of Si, and followed by N2 annealing. X-ray diffraction results indicate that the fabricated samples contain β-SiC particles which may exist in the pores, in addition to Si, SiO2, and graphite. The pho…
Neodymium-doped polyimide waveguides were studied for optical amplifier applications. Photoluminescence at 890 nm, 1.06 μm, and 1.33 μm from neodymium ions in the polymer matrix was observed. Optical gain of about 8 dB was measured at 1.06 μm in a 5-cm-long multimode channel waveguide. Phase separation was observed in…
Theoretical investigations (density-functional tight binding) about the changes of the properties of single-wall carbon nanotubes (SWNTs) by fluorination are reported. It is shown that a sidewall functionalization of SWNTs may lead to tubes with a wide variety of electronic properties, ranging from insulating over sem…
The local atomic order of semiconducting liquid GeTe is studied using first-principles molecular-dynamics simulations. Our work points out a high degree of alternating chemical order in the liquid and demonstrates the presence of a Peierls distortion close above the melting temperature. This distortion, absent in the…
Rare-earth intermetallic compounds (Tb1−xGdx)Al2, have been successfully fabricated and characterized. Large magnetic entropy change, ΔSM, was observed in these alloys. The maximum −ΔSM(=14.3 J/kg K) is achieved in the TbAl2 alloy at its Curie temperature, TC=105 K, with a 5 T magnetic field change. It is shown that t…
Ultrafast spin dynamics in ferromagnetic half-metallic compound Sr2FeMoO6 is investigated by pump-probe measurements of the magneto-optical Kerr effect. The half-metallic nature of this material gives rise to anomalous thermal insulation between spins and electrons and allows us to pursue the spin dynamics from a few…
The dynamic susceptibility study of photoinduced magnetism in a molecule-based magnet, ${\mathrm{K}}_{1\ensuremath{-}2x}{\mathrm{Co}}_{1+x}[\mathrm{Fe}(\mathrm{CN}{)}_{6}]\ifmmode \dot{}\else \.{}\fi{}y{\mathrm{H}}_{2}\mathrm{O}$ $(0.2\ensuremath{\le}x\ensuremath{\le}0.4,y\ensuremath{\sim}5)$, is reported. Upon excita…
In weakest link models the failure of a single microscopic element of a brittle material causes the failure of an entire macroscopic specimen, just as a chain fails if one link fails. Pristine samples of glass, such as optical communications fiber, approach their ideal strength, and their brittle tensile failure has b…
We study by numerical simulations the scattering of $s$-polarized light from a rough dielectric film deposited on the planar surface of a semi-infinite perfect conductor. The dielectric film is allowed to be either active or passive, situations that we model by assigning negative and positive values, respectively, to…
An eight-potential-well order-disorder ferroelectric model was presented and the phase transition was studied under the mean-field approximation. It was shown that the two-body interactions are able to account for the first-order and the second order phase transitions. With increasing the random fields in the system,…
We present a model to find analytically the electronic states in self-assembled quantum dots with a truncated spherical cap (`lens') geometry. A conformal analytical image is designed to map the quantum dot boundary into a dot with semi-spherical shape. The Hamiltonian for a carrier confined in the quantum lens is cor…
Holographic techniques significantly extend the capabilities of laser tweezing, making possible extended trapping patterns for manipulating large numbers of particles and volumes of soft matter. We describe practical methods for creating arbitrary configurations of optical tweezers using computer-generated diffractive…
We study a recently proposed nonlinear evolution equation describing the collective step meander on a vicinal surface subject to the Bales-Zangwill growth instability [O. Pierre-Louis et al., Phys. Rev. Lett. (80), 4221 (1998)]. A careful numerical analysis shows that the dynamically selected step profile consists of…