Materials Literature
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Lead monohydrogen phosphate (PbHPO 4 ) undergoes a ferroelectric phase transition at T c =310 K at atmospheric pressure. T c falls to room temperature at a pressure of about 0.125 GPa. The crystal structure of PbHPO 4 has been determined by X-ray diffraction at 2.0 and 2.3 GPa and the lattice parameters have been meas…
For the crystallization of proteins under microgravity conditions, a Chinese re‐entry system was used, in which 101 experiments of 25 different biological macromolecules were accommodated. From the results obtained we conclude that under microgravity conditions crystal growth can only be expected under those crystalli…
We present experimental evidence of the smectic-A (${S}_{A}$) phase in colloidal solutions of tobacco mosaic virus. The smectic-A phase is determined by the observation of a layered structure along the virus alignment direction and a liquidlike order within layers. In our samples, we also observed the characteristic $…
We have measured Raman spectra of diamond films prepared by a hot-filament method and found that diamond layers on Si substrates are under compressive strain. The degree of the strain is found to increase with increasing nondiamond component in the diamond films. It is shown that Raman spectroscopy is a powerful metho…
For pt.I see ibid., vol.21, p.1423 (1988). Several transition-metal compounds show a transition from the low-spin to the high-spin electronic state with increasing temperature. The cooperative nature of the transition in the solid state is attributed to the elastic interaction between the spin-changing ions as a resul…
The temperature dependence of x-ray peak intensities of icosahedral AlCuFe is studied in detail. Above 670 \ifmmode^\circ\else\textdegree\fi{}C, measurements of the Debye-Waller factor suggest the presence of dynamical phasons. Softening of the phason modes drives a structural transition at \ensuremath{\sim}670 \ifmmo…
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…