Materials Literature
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We report light-scattering measurements of powder diffraction patterns of crystals of essentially hard colloidal spheres. These are consistent with structures formed by stacking close-packed planes of particles in a sequence of permitted lateral positions, A,B,C, which shows a high degree of randomness. Crystals grown…
For single-phase polycrystalline materials the relation is discussed between the elastic strain ϵ(ψ, φ) obtained from X-ray diffraction experiments and the polynomial expansion of the stress components σφ(σ) and σφ+90(z) with respect to the distance z from the external surface of the specimen. A universal plot is prop…
The charge-transfer (CT) interactions in electroactive polymeric complexes formed by nonconjugated polymers: poly-2-vinylpyridine, poly-4-vinylpyridine, and various halobenzoquinone electron acceptors such as: o-chloranil, p-chloranil, o-bromanil, and p-fluoranil have been investigated by means of x-ray photoelectron…
The fully oxidized form of polyaniline, pernigraniline, is studied in the framework of a Su-Schrieffer-Heeger-like Hamiltonian. The protonation process of a long oligomer is investigated. Protonation is modeled by a change in site energies around the protonated site. The results of the calculataions indicate that a ph…
Recently M. Tokunaga has published two interesting papers (J. Phys. Soc. Jpn. 56 (1987) 1653; 57 (1988) 4275) that relate the fluctuating polarizations p c in the paraelectric phases of ferroelectrics (estimated from the Curie constants determining the dielectric susceptibilities) and the spontaneous polarizations P S…
The translational diffusion coefficient D of long enough polymer chains without excluded volume is studied on the basis of the discrete helical worm-like (HW) chain with partially fluctuating (orientation-dependent) hydrodynamic interaction (HI). In order to evaluate D(∞) in the long time limit, which corresponds to d…
We present band-structure calculations of ${\mathrm{SnTaS}}_{2}$, an intercalation compound in which the Sn atoms have a very uncommon linear coordination by two S atoms and an unusual formal valency ${\mathrm{Sn}}^{1+}$. The Sn 5${p}_{x}$ and 5${p}_{y}$ states show strong metal-metal bonding in the intercalant planes…
We report the observation of 1/frequency magnetization noise in toroidal strip-wound cores of amorphous ferromagnetic alloys at liquid-helium temperatures and in the frequency range 0.1 Hz–1 kHz. The materials tested are Co-based alloys, and exhibit very low magnetostriction and good soft magnetic properties. The expe…
Layer Korringa-Kohn-Rostoker (LKKR) approaches that calculate interlayer scattering using a plane-wave basis set cannot treat systems in which the interplanar spacing becomes small. This problem is most acute at band energies at which electronic lifetimes are long and the scattering strong. Taking a face-centered-cubi…
The important role atomic hydrogen plays in the low-temperature and pressure deposition of diamond has renewed interest in the dissociation processes of hydrogen. Following a method originally developed by Langmuir and co-workers, the voltage-current characteristics of refractory filaments in vacuum and reduced-pressu…
The charge-transfer mechanism in 1,4 cis-polyisoprene is studied using solid state 13C NMR spectroscopy as a function of doping level of iodine. The CP/MAS NMR data show that the concentration of double bonds decreases as a consequence of doping. The overall results are consistent with previous observations and indica…
A solgel process is described to produce Ta(2)O(5) films as short wavelength antireflective (AR) coatings for silicon. The AR coatings were optimized for 370 nm by controlling the acid catalyzed hydrolysis of Ta(OC(2)H(5))(5), the spin coating parameters, and the heat treatment process (rapid thermal processing (RTP)…
The application of the algorithm of Zeiger and McEwen to the analysis of noisy photon correlation data is investigated. For the particular case where the data are sampled at equidistant time intervals a complete solution is given allowing reliable reconstruction of the spectrum of exponential decay rates without any a…
Cristallisation dans Cc avec a=17,250, b=9,767 et c=17,106 A, β=110,9 o , Z=32; affinement jusqu'a R=0,0289. La structure consiste en tetraedres PO 4 discrets lies par des tetraedres ZnO 4 et LiO 4 deformes de sorte que trois tetraedres differents partagent un sommet. Bien que des couches de tetraedres paralleles a (0…
Cristallisation dans Cm avec a=8,129, b=16,051 et c=3,5390 A, β=100,94 o , Z=2; affinement jusqu'a R=0,038. La structure contient des ions Ca 2+ coordines octaedriquement par des atomes O et F et des anions (BO 3 ) 3− qui sont principalement responsables de l'effet de generation d'harmonique secondaire
From 15 K to room temperature, dielectric and pyroelectric properties have been measured in six ferroelectric niobate single crystals with tungsten-bronze (TB) structure. Dielectric and pyroelectric experiments show that in the three kinds of ferroelectric niobate single crystals ${\mathrm{Sr}}_{1\mathrm{\ensuremath{-…
ZnS thin films were deposited with and without ion assisted deposition onto substrates held at temperatures ranging from -120 to 50 degrees C. Effects on chemical and crystalline composition, film microstructure, refractive index, stress, and waveguide losses were investigated. We observed that minimum stress and mini…
With an ultralow load indenter the hardness H and the Young’s modulus E of amorphous hydrogenated carbon and silicon films, prepared under different conditions, were determined. The values of the hardness of a-C:H, corrected for the elastic recovery, are about 1/3 of the values measured by the Knoop method. The result…
We show by transport properties and electron-microscopy measurements that a polytype of ${\mathrm{NbS}}_{3}$ undergoes a Peierls transition at 340 K. Similarly to other transition-metal trichalcogenides and tetrachalcogenides, ${\mathrm{NbS}}_{3}$ exhibits charge-density-wave transport for temperatures below the phase…
Nematic LC material in the aligned state scatters light strongly, but in low loss LC cored fiber waveguides it scatters less and has enhanced recovery time.