Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
We propose a structure for the self-trapped exciton in \ensuremath{\alpha}-quartz on the basis of ab initio Hartree-Fock cluster calculations. It involves the displacement of a single oxygen atom in a direction nearly parallel to the hexagonal axis so that the shorter of its two silicon-oxygen bonds is lengthened. The…
Rapidly solidified Nd-Fe-B ribbons were crushed and mixed with a fine powder (10–100μm) of a pure element before hot working into fully dense anisotropic magnets. At the high temperatures and pressures required for densification some additives diffused throughout the ribbon matrix and presumably into the neodymium-ric…
An elementary introduction on direct and resonant low-energy (0-20 eV) electron scattering from molecules condensed on surfaces is given with reference to concepts developed from gas-phase investigations. It is shown that while elastic scattering can be described in terms of band-structure parameters, inelastic proces…
The random-loose-packing fraction of uniform spheres at the limit of zero gravitational force is determined to be 0.555\ifmmode\pm\else\textpm\fi{}0.005. This structure corresponds to a sphere packing at its rigidity-percolation threshold. The onset of dilatancy was also measured to be at approximately the same packin…
A large single crystal (18×40×15 mm3) of a new nonlinear optical material ‘‘chalcone derivative’’ has been grown by an evaporation method. This crystal was relatively easy to grow to a large size and was chemically stable. The cutoff wavelength was 430 nm. The calculated phase matching angles for the second-harmonic g…
Abstract The preparation process of amidoxime hollow fiber consists of three steps: (1) radiation‐induced graft polymerization of acrylonitrile (AN) onto porous hollow fiber (AN grafting), (2) chemical conversion of the cyano group into an amidoxime group (amidoximation), and (3) conditioning of the hollow fiber with…
Abstract The behavior of the secondary electron emission (SEE) from organic solids has been considered. It has been shown that the maximum SEE yields of many hydrocarbon compounds exponentially depend on the extinction coefficient of secondary electron defined by the π‐electron fraction in molecule, which is correlate…
EPR measurements of Cr-doped SnO2 crystals are made at room temperature using an X-band spectrometer. A new EPR spectrum is observed for as-grown crystals. The orientation of the paramagnetic principal axis deviates from the [110]-axis by angles of ±4.2° in the (001)-plane. The spin-Hamiltonian parameters are determin…
Experiences on crystal growth of calcite doped with Pb2+ using the method of travelling solvent zone melting (TSZM) are reported. Optical absorption, polarized luminescence, excitation spectra, decay times and relative quantum yields of the Pb2+ centres are studied in their temperature dependence. The properties found…
A new continuously tunable color filter, which uses smectic A(*) liquid-crystal half-wave plates, is described and experimentally demonstrated. Multiple-stage Lyot filters with broad tunability and high finesse can be constructed with this design. The transmission characteristics of a single-stage filter, which is con…
We have developed a site-selective laser method to study the aggregation kinetics of defect sites as a result of heat treatment in ${\mathrm{EuF}}_{3}$-doped ${\mathrm{CaF}}_{2}$ crystals. The crystals contain ${\mathrm{Eu}}^{3+}$ in four dominant defect sites and one minor site that differ in the number of nearby dop…
The temperature dependence of Raman spectra of lithium diborate (Li 2 B 4 O 7 ) was measured at temperature range from 300 K to 900 K. At room temperature, 12 A 1 , 12 B 1 , 15 B 2 and 22 E modes were observed by various scattering geometries. No soft mode was observed in the above temperature range, implying that no…
We report calculations of the electronic structure of a model of ${\mathrm{TiO}}_{2}$ which contains oxygen vacancies. The model uses the full tight-binding model of Vos. We use a screened Coulomb potential and a soft positive core to describe the oxygen vacancy. We study the electronic density of states as a function…
The linear muffin-tin orbitals (LMTO) method is used to calculate the self-consistent spin-polarized electronic structures of ${\mathit{R}}_{2}$${\mathrm{Fe}}_{14}$B (R=Y,Nd) compounds. The present results are compared with those of an earlier non-self-consistent calculation. The calculated results are in good agreeme…
The two tin oxides, SnO and ${\mathrm{SnO}}_{2}$, are not easily distinguished by their core x-ray photoelectron spectroscopic regions, but have significantly different valence-band regions. In addition, significant differences exist in the separations between the near-core region and the valence-band region. These di…
Low-temperature (10–300 K) dielectric and pyroelectric properties of morphotropic-phase-boundary lead-barium-niobate tungsten-bronze ferroelectric single crystals have been investigated. Strong ‘‘Debye-like’’ dielectric dispersion, along a nonpolar direction (perpendicular to the polarization direction), has been obse…
An analysis is presented of the growth of silver aggregates in the size range 10--200 \AA{} on an amorphous carbon substrate (a-C). It is found that growth at this submicroscopic scale exhibits the main statistical properties observed on a scale of ${10}^{\mathrm{\ensuremath{-}}3}$--1 mm in the patterns formed when a…
We present the results of spectroscopic studies of the electronic structure of the conjugated polymer poly(2,5-thienylene vinylene). Photoexcitation above the band gap at 1.8 eV gives rise to two transient absorption peaks at 0.44 and 1.0 eV that are associated with bipolarons that live for times of order a few millis…
In order to clarify the role of hydrogen in diamond synthesis using a microwave plasma in a CO/H2 system, carbon films were grown by varying hydrogen mole fractions in a CO/H2/He microwave plasma. The correlation between film properties and plasma species was investigated through film characterization and plasma emiss…
The dielectric relaxation function is defined as the transient current generated by the application of a unit voltage. In analogy with viscoelasticity, a second relaxation function can be defined as the transient voltage generated by the application of a unit current. Each of these functions generates its own distribu…