Materials Literature
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Mr=393.26, monoclinic, P2 1/ c, a=13.8937 (14), b=9.6258 (7), c=10.9127 (7) Aring, beta=95.66 (1)deg, V=1452.3 (2) Aring 3, T=295K [the cell parameters were determined from the refinement of 39 theta values from a Guinier-Hagg X-ray powder film (Cr Kalpha radiation, lambda=2.28975 Aring, using a CoP 3 standard: a=7.70…
Using the synchrotron-radiation facility at Brookhaven National Laboratory, we have studied the electronic structure of thin hydrogenated amorphous carbon films produced by dc glow discharges of hydrocarbons. Valence-band photoemission measurements on these films yielded information on the occupied valence-band densit…
This paper describes how the Hubbard model in the atomic limit implemented by taking into account molecular vibrations can give a description of mixed valence binuclear systems with both metallic ions simultaneously magnetic. A FeIII (high spin) FeII (high spin) binuclear complex would constitute an example. In such s…
High-resolution time-of-flight measurements of 17-meV He atoms scattered from an Ag(111) surface along the $〈112〉$ and $〈110〉$ azimuths are reported. Most of the spectra reveal two sharp peaks and from their locations dispersion curves have been determined out to the zone boundary. The agreement of the lower-frequency…
A model for the temperature variations of the thermoelectric power (TEP) of acceptor graphite intercalation compounds (GIC's) is presented. At low temperatures, the TEP in GIC's increases monotonically with $T$, then levels off above \ensuremath{\sim}200 K in striking contrast to that of pristine graphite. The diffusi…
ESR measurements have been performed on samples of neutral polypyrrole, polypyrrole-perchlorate, oxygen-doped polypyrrole, and poly($\ensuremath{\beta}$,${\ensuremath{\beta}}^{\ensuremath{'}}$-dimethylpyrrole perchlorate). A narrow Lorentzian line is observed in oxidized, highly conducting films, but no correlation be…
Angle-resolved core-level and valence-band x-ray photoelectron spectroscopy (XPS) data for GaAs(110), Ge(110), and Ge(111) surfaces are analyzed to determine core-level to valence-band maximum binding-energy differences to a precision of the order of the room-temperature thermal energy. A method for markedly improving…
The microscopic mechanisms responsible for both the formation and coupling of magnetic moments in Heusler alloys (${X}_{2}\mathrm{Mn}Y$) are identified. We find that the $X$ atoms (e.g., Cu, Pd) serve primarily to determine the lattice constant, while the $Y$ atoms (e.g., Al, In, Sb) mediate the interaction between th…
Inelastic electron scattering is calculated by means of a simplified model of the generalised oscillator strength density distribution of an atomic or solid target. The parameters of the model are a limited set of resonance energies (partial mean ionisation potentials) and oscillator strengths. Methods to estimate the…
The authors review the use of the ideas of 'ionicity' and 'covalency' in quantitative studies of the solid state. Such ideas have taken several distinct forms: a description of charge distributions of bonding, a spectroscopic classification of perfect solids, and a framework for quantitative modelling of defects in po…
The problem of minimizing the full cholesteric free energy in flat space is difficult since the bending and bulk energies favor different forms of the order parameter. It is shown, however, that the problem can be solved exactly on the surface of a sphere in four-space, where the curvature relieves the strains induced…
Abstract The chain-of-bundles model for the strength of unidirectional fibrous materials is extended to cover 3D situations wherein the parallel filaments are arranged laterally in a hexagonal array. Within each bundle, the strengths of the fibres vary statistically and share load according to a local load-sharing rul…
Two new effects specific to ferroelectric liquid crystals are described: (a) ferroelectric polar surface interactions and (2) spontaneous splay of the polarization. It is shown that a consequence of these effects is the possibility of first-order reorientation transitions induced by applied electric fields.
Sillimanite in six granulite-facies, kornerupine-bearing rocks contains 0.035 to 0.43 percent B(2)O(3) and 0.02 to 0.23 percent MgO (by weight). Substitution of boron for silicon and magnesium for aluminum is coupled such that the ratio of magnesium to boron is about 0.5. Sillimanite incorporates more than 0.1 percent…
Abstract Cyclotetraphosphate K 2 Pb[P 4 O 12 ] transforms into the lead diphosphate Pb 2 P 2 O 7 crystallographically oriented by heating up to its transformation point at 537°C in a moist atmosphere. The oriented formation of diphosphate takes place by means of epitaxy.
60 Hz and dc corona inception voltage is measured in solid-air composite insulation systems under electrical fields of varying degree of non-uniformity. Residual field due to charges deposited on the insulator surface, using dc voltages, is also measured and its influence on corona inception phenomena is discussed. Th…
Monoclinic AsSbO 3 was prepared by heating an equimolar mixture of AS 2 O 3 and Sb 2 O 3 to 670 K in an evacuated quartz tube. The crystal structure was determined [P2 1 /n, a = 458(1), b = 1316(2), c = 544(1) pm, β = 95.0(1)°, Z = 4, R = 0.055 for 745 reflections] and found to be isostructural with the As 2 O 3 modif…
Abstract Im System GeO 2 /WO 2 wird mit Hilfe eines verbesserten thermodynamischen Rechenprogramms die Gleichgewichtszusammensetzung der Gasphase und des Bodenkörpers bei Temperaturen 1100 < T < 1400 K für konstantes Volumen berechnet. Auf Grund der Ergebnisse kann die bei Experimenten in evakuierten, zugeschmol…
The effects of hydrostatic pressure on a ferroelectric compound of NH 4 HSO 4 have been investigated with the static, dynamic dielectric and pyroelectric measurements. It has been found that the tricritical point of NH 4 HSO 4 exists at the temperature of 6.5°C and the pressure of 750 bar. The dielectric critical slow…
Abstract The refractive index dispersion of different arsenic chalcogenide glasses is analyzed by the use of a two‐term Sellmeier dispersion formula. In a region from 3 μm up to the beginning of the absorption edge the wavelength dependence of the refractive index can be described by a single oscillator model. At wave…