Materials Literature
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A new class of crystalline structures for group-IV materials is proposed. The basic building block for all the new structures is a two-dimensionally ordered slab of atoms which can be stacked together in several distinct ways. The most stable structure obtained in this way has a 20-atom orthorhombic unit cell. For Si,…
A digitonin-solubilized cellulose synthase was prepared from Acetobacter xylinum. When this enzyme was incubated under conditions known to lead to active synthesis of 1,4-beta-D-glucan polymer (cellulose), electron microscopy revealed that clusters of fibrils were assembled within minutes. Individual fibrils are 17 +/…
We consider the propagation of bulk and surface plasmons in a finite superlattice structure composed of alternating layers of materials A and B, with the whole structure resting on a substrate. An implicit dispersion relation is derived allowing the dielectric constant of each material to be a function of frequency. W…
Perturbation calculations are performed for 〈R2〉, 〈S2〉, 〈RH〉, A2, and A3 for polymers near the theta point using a continuous curve representation of the three-parameter theory of Yamakawa. Both dimensional regularization and cut-off schemes are employed, but only the latter method is shown to be in accord with observ…
The band gap and quasiparticle energies in LiCl are calculated by evaluation of the electron self-energy operator including the effects of local fields and dynamic screening from first principles. Good agreement with available experimental data is obtained. In particular, the calculated band gap for bulk transitions (…
The 0.875-eV (Ga1) photoluminescence defect spectrum in gallium-doped irradiated silicon is studied in high resolution and in uniaxial stress and homogeneous magnetic fields. The spectrum exhibits one- and two-phonon Stokes satellites of the no-phonon Ga1 line due to the coupling of quasilocalized vibrational modes of…
Magnesium self-diffusion in MgO crystals has been studied over the temperature range 1100--1250 K with the use of the nuclear reaction $^{18}(\mathit{p}$,\ensuremath{\alpha})${}^{15}$N. Magnesium drift due to an electric field was determined, and from the buildup of Mg $^{18}$O at the cathode, diffusion coefficients a…
fl l-V2H: M r = 102.89, tetragonal, I4~/amd, a = 6.0349 (4), c = 6.8716 (3)/k, V = 250.3 A 3, D x = 5 . 4 6 M g m -3, Z = 8 , 2 (MoKa)=0 .7107 /k , /~= 13.65 mm -1, F(000)= 376.0, room temperature, final R-0 .031 for 154 independent reflections; fl-V2D: M r = 103.9, monoclinic, Cm, a = 4 . 4 5 5 4 ( 7 ) , b = 3.0090 (…
Decay curves and spectral shapes of the singlet-exciton luminescence in anthracene crystals have been studied at room temperature and found to depend on the experimental geometry and on the penetration depth of the exciting light. The well-known wavelength-dependent decay time and time-dependent spectrum occur only wh…
We have developed a theory of low-temperature thermal expansion of glasses explaining a number of existing experimental data. We assume that thermal expansion, like many other low-temperature properties of glasses, is determined by associated two-level systems (TLS's); this concept has been introduced to explain these…
Full-potential self-consistent linearized augmented-plane-wave calculations for hexagonal boron nitride show the existence of unoccupied interlayer states similar to those found in pure and intercalated graphite. Furthermore, in contradiction to the currently accepted picture, the resulting energy-band structure indic…
We investigated experimentally the coupled modes of surface plasmons in periodically corrugated thin silver films in a thickness range from 26 to 121 nm. The films studied were self-supporting and corrugated with a period of 1888 nm and amplitudes varying from 6 to 12 nm, depending on the film thickness. Propagation a…
The local magnetic moment M loc , the hyperfine field H hf and the nuclear spin-lattice relaxation time T 1 of 3 d and 4 d transition metal impurities in Fe are calculated in the framework of the Green function method and in the local spin density approximation (LSD). The calculation reproduces the observed major tren…
The structure transition Ir(100) 1\ifmmode\times\else\texttimes\fi{}1\ensuremath{\rightarrow}1\ifmmode\times\else\texttimes\fi{}5 is observed by means of low-energy electron diffraction. After the preparation of the metastable and bulklike 1\ifmmode\times\else\texttimes\fi{}1 surface structure the transition is starte…
The reflectivity spectra of the ${\mathrm{BaPb}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Bi}}_{\mathrm{x}}$${\mathrm{O}}_{3}$ alloy series are investigated over a wide energy range, 20--30 000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, and over the whole compositional range. As the Bi composition x is increase…
The thermal conductivity between 12 and 300 K is reported for graphite fibers carbonized from a variety of precursors, including spun polyacrylonitrile, petroleum pitch, or grown by chemical vapor deposition of methane. The fibers were studied as grown as well as heat treated to temperatures up to 3000 \ifmmode^\circ\…
The electronic structure of surface defects on NiO(100) and their interaction with ${\mathrm{O}}_{2}$ and ${\mathrm{H}}_{2}$O have been studied on single crystals cleaved in ultrahigh vacuum by using ultraviolet and x-ray photoemission and Auger spectroscopies, as well as low-energy-electron diffraction. Defects creat…
The idea that the ratio E/D ≡ λ can be confined by a proper choice of the axis system to the range (0,±1/3) serves as a basis for the standardization of the spin Hamiltonian and the ligand field Hamiltonian for orthorhombic symmetry. Due to recent results on the transformation of the Stevens operators Oqk, relations a…
Beer foam is reviewed in terms of the physical principles which underly it, its measurement and the components of beer which affects its formation and stability. The influence of processing conditions on foam production, retention and cling are detailed.)
The importance of three-dimensional effects in the electronic structure of the quasi two-dimensional layered crystal $1T$-Ti${\mathrm{Se}}_{2}$ is demonstrated by means of high-resolution angle-resolved photoemission excited by synchrotron radiation. By resolving the spin-orbit splitting of the upper Se-$4p$ valence b…