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The optical absorption edge of undoped, lightly Al-doped, and heavily Al-doped Bi12SiO20 single crystals is found to be exponential and follows Urbach's rule with σ0=0.71 at room temperature. The band edge is at 3.25 eV and is broadened by excitons and perhaps by impurities or defects. At 80 °K, the band edge is found…
Abstract The possibility to calculate magnetic moments in elemental disordered systems (amorphous state, lattice distortions, surfaces) using the inhomogeneous electron‐gas model is considered. Therefore a partial summation of the gradient expansion of the kinetic energy density functional is performed, which allows t…
The purpose of this type of experiment is to elucidate structure of the different compounds gradually prepared starting from reaction mechanisms and chiefly from spectroscopic data given perviously to students.
Abstract Electron paramagnetic resonance has been studied for divalent titanium with 3d 2 configuration substituting for Cd in hexagonal single crystals of cadmium sulphide and cadmium selenide. The parameters of the spin‐Hamiltonian have been determined at T = 27 and 77 K. It is found that the symmetry of the centre…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic studies of permanganate oxidation reactions. IV. Reaction with bromide ionSamuel A. Lawani and John R. SutterCite this: J. Phys. Chem. 1973, 77, 12, 1547–1551Publication Date (Print):June 1, 1973Publication History Published online1 May 2002Published inissue 1 June 1…
A numerical model is presented which describes the strain level build-up in yarns due to multiple strain wave reflections from yarn crossover intersections in a woven fabric subject to ballistic impact. Crossing yarns present barriers from which strain waves are partially reflected. The maximum yarn strain occurs at t…
The effect of dielectric constant on surface discharge of polymer insulators (polyethylene, polycarbonate, polytetrafluoroethylene, and polyamide) with right cylindrical shape was investigated. The experimental results showed that dc flashover voltage was decreased with increase of dielectric constant in polymers.
Binary Sb 2 O 3 ‐GeO 2 glasses containing 45 mol% Sb 2 O 3 and ternary Sb 2 O 3 ‐B 2 O 3 ‐GeO 2 glasses containing 50 mol% GeO 2 were prepared. Their densities (volumes), refractive indices, and infrared spectra were determined, and their colors and high‐temperature viscosities were estimated visually. Small amounts o…
Abstract The optical properties of SiTe 2 have been studied in the region 2.5 to 0.5 μm and in the temperature range 300 to 100°K. In the absorption spectrum three distinct regions have been observed which have been attributed to Te vacancies, indirect, and direct transitions, respectively. The fine structure in the v…
The ionization energies of some iron-sulphur compounds are reported and discussed. The nature of the chemical bond between iron and sulphur varies between ionic and practically pure covalent. Multiplet-splittings in the Fe3s level are observed in the photoionization resulting from the spin orientation of the 3d electr…
Abstract [(CH 3 ) 2 AIOCH 3 ] 3 has been studied by gas phase electron diffraction. The mainmolecular parameters are R(A1C) = 1.957(3) Å, R(A10) = 1.861(3) 8, R(0C)= 1.436(3) Å, <CAIC = ll7.3(0.8)°, <0A10 = 103.2(1.1)° and (AIOAl = 125.8(0.4)°. The three valences of the 0 atoms appear to be lying in one…
X-ray and neutron-diffraction techniques have been used to ascertain the structures of vanadium deuterides with compositions between V2D and V4D3 over a temperature range 5–425 °K. The β phase, V2D, has a monoclinic crystal structure at room temperature with a≃c = 4.46; b = 3.00 Å, β = 95.5°. The deuterium atoms prefe…
A new scanning transmission electron microscope has been built which uses a lanthanum hexaboride thermal cathode electron gun. Initial results indicate a beam diameter of 5 Å and point-to-point resolution of 7 Å. The vacuum level in the instrument is similar to that of standard commercially available electron microsco…
Summary A new variety of heterogenite was found in samples from Mindigi, Shaba, Zaïre. Photometric reflectance varies from 0·235 to 0·165 at λ 5890 Å in air. The bireflectance is 0·070, the degree of anisotropy is 0·7 and the main index in air is 2·7. A thermal weight-loss curve and a microprobe analysis are given and…
Separate plus and minus cultures of Blakeslea trispora synthesize small amounts of trisporic acids under specific conditions. These amounts are expressed as a percentage of the trisporic acids (50 mg/liter of medium) synthesized by mixed plus-minus cultures in 5 days. Plus cultures, without additives from minus cultur…
The elastic properties of polycrystalline monoclinic Gd 2 O 3 were determined by the sonic‐resonance method. Volume‐fraction porosity varied from 0.025 to 0.367 and temperature from room temperature to 1400°C. The Young's and shear moduli are linear functions of volume‐fraction porosity, but the rate of their decrease…
Seven T1u infrared active modes account for the pyrochlore structure. Decreasing A3+ cation size in the rare-earth zirconates increases disorder among the cations and the tendency to form the fluorite structure. There is a general trend of increasing absorption frequencies with smaller cell sizes for the higher-wave-n…
LiSn crystallizes monoclinic: a = 5.17 ± 0.02 Å; b = 7.74 ± 0.02 Å; c = 3.18 ± 0.02 Å; γ = 104.5° ± 0.3°, space group: P 2/m - C 2h 1 . LiSn is not isotypic with LiGe and LiPb, but there are many structural relations to LiPb.
Abstract A simple electrostatic model has been used to demonstrate that the inner surface hydroxyls in kaolinite, dickite and nacrite are responsible for the interlayer bonding in these minerals. The contribution to the interlayer bonding of an individual hydroxyl hydrogen depends on the orientation of the hydroxyl gr…
Abstract This article emphasizes the influence of crystal-chemical composition on the ease of transformation of micas to vermiculite or more smectite-like minerals. The swelling test, with glycerol, of Mg-saturated mineral is used to characterize the degree of transformation. The main structural factors of this evolut…