Materials Literature
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The theory of kinematic X-ray diffraction from dislocated crystals as developed in [1] is extended to crystals containing more than one set of straight parallel dislocations. The Bragg reflexion line broadening is expressed by two parameters of the dislocated crystal, the dislocation density, ϱ, and the effective oute…
Energy bands are calculated for hexagonal NiS using lattice constants and crystal potential appropriate to the metallic phase. Group theoretic results for $s$, $p$, and $d$ bands in the NiAs structure are obtained, and the calculation is performed using a first-principles tight-binding method. The energy band structur…
The infrared absorption in $n$-type InP was studied as a function of free-carrier concentration from 3.5\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to \ensuremath{\sim} ${10}^{19}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ in the spectral range of 10 \ensuremath{\mu} to the fundamental absorption edge. The Burstein shifted…
The optical absorption of vanadate glasses based on the system V2O5–P2O5 was measured in the range 20 cm−1 to 25 000 cm−1 at room and liquid-nitrogen temperatures. The samples were blown films of thickness about 1–2 μ and of composition 70.0, 80.0, and 87.5 mole % V2O5. Vibrational absorption peaks were observed at ab…
Amorphous alloys having the composition ${({\mathrm{Ni}}_{x}{\mathrm{Pt}}_{1\ensuremath{-}x})}_{0.75}{\mathrm{P}}_{0.25}$, where $0.20\ensuremath{\le}x\ensuremath{\le}0.60$, were obtained by rapid quenching from the liquid state. X-ray diffraction measurements indicate a high degree of structural disorder in these all…
A proton magnetic resonance spin–lattice relaxation and second moment study of the ferroelectric transitions in diglycine nitrate (DGN), trissarcosine calcium chloride (TSCC), and its deuterated analog has been performed. The results support the order–disorder model of the ferroelectric transition in these compounds a…
The crystal structure of [OCr3(CH3COO)6.3H20]+C1 -. 6H20 has been determined from three-dimensional diffractometer data using Cu Ke radiation. The configuration of the complex cation consists of three chromium atoms linked to a central oxygen atom in a planar configuration. Each chromium atom is coordinated octahedral…
A comparison between the ultraviolet-reflectivity spectrum and the characteristic energy-loss spectrum of ZnO has been carried out. Reflectivity measurements made over an energy range of band gap to 22 eV yielded a spectrum with structure at 3.34, 5.0, 7.3, and 8.4 eV, and in the region 11-15 eV. Energy-loss measureme…
The theory of dielectric relaxation in a model polar liquid is developed and applied to experimental data. The model is a spherical Onsager cavity, with a uniform dielectric background described by the high frequency limit ε∞ and containing a permanent point dipole. The dipole moment undergoes rotational Brownian moti…
The 5D emissions of Eu3+ in Y2O2S, La2O2S, and LaOCl quench sequentially with increasing temperature in the simple order 5D3, 5D2, 5D1, 5D0. These 5D quenchings are attributed to thermally activated resonance crossovers from the 5D states to the charge-transfer states (CTS). The activation energies for the 5D quenchin…
The electronic band structure of graphite has been calculated from an ab initio variational approach using a linear-combination of atomic-orbitals (LCAO) basis of Bloch states, including nonspherical terms in the one-electron crystal potential. Matrix elements of the Hamiltonian are evaluated directly without any tigh…
El presente trabajo comprende el estudio taxonómico de catorce especies de equinoides, de las que diez son regulares y cuatro son irregulares. Entre las irregulares, dos especies son nuevas: Heteraster aguilerai n. sp. y Heteraster alencasterae n. sp. La colección de equinoides estudiada proviene de las formaciones Za…
The far-infrared spectra of thin films of PH4Cl and PD3Cl have been recorded at −170°C. Raman spectra of polycrystalline samples of both compounds were also recorded at −170°C. One libration and three translations were observed as well as eight internal modes. Several combinations and overtones were assigned and the z…
Some relationships between crystal textures and their permanent magnet properties are reviewed on the basis of a homogeneous uniaxial anisotropic ferromagnet and a mosaic grain agglomerate in the commercial size of an Alnico 8 alloy. From the results obtained, it has been concluded that the highest energy might be obt…
Solutions of N 2 O in liquid formamide (dielectric constant 109) gave a yield of N 2 during γ-radiolysis of G(N 2 ) = 3.3 ± 0.3. Competition between N 2 O and other scavengers, including water, ethanol, acids, AgNO 3 , and CdI 2 strongly resembled the pattern of reactivity characteristic of solvated electrons found in…
The paper reviews the development and application of tungsten halogen lamps since their first introduction. The halogen cycle is described and the advantages of using bromine compounds in the fill gas of some halogen lamps are indicated. Many problems have arisen from the use of halogens; the ways in which these have…
The energy distribution of electrons in a part of the electron beam selected by two apertures situated on the axis was measured using a wienfilter-type energy analyser. These measurements gave brightness values for electrons in specific energy intervals of the distribution which fitted the theory extremely well. The i…
Single crystals of Al 2 O 3 (sapphire) were grown from PbO‐PbF 2 and MoO 3 ‐PbF 2 fluxes; they varied from flat plates (PbF 2 ‐rich melts) to equidimensional crystals (PbO‐ or MoO 3 ‐rich melts). The primary growth planes are basal {0001}, first‐order rhombohedral {1011}, and second‐order rhombohedral {0112}. The habi…
For Alnico alloys containing 32-42 percent Co, 0-9 percent Ti, 6-8 percent Al, 14 percent Ni, 3 percent Cu, 0-0.5 percent S, 0-2 percent Nb, remainder Fe, the liquidus and solidus temperatures and the upper limit of the (α + γ) phase field were determined. The greatest influence is exerted by titanium in that all temp…
Precipitation and dissolution potentials for KCl, NaCl, BaCl2, and NH4Cl have been measured with a Lindemann electrometer both in air as well as in nitrogen. The values in the latter case are lower. The electrode on which precipitation and dissolution takes place is found to be negative. The available evidence shows t…