Materials Literature
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Structural phase transitions are investigated in crystals of the isostructural compounds MRA2 (M alkali metal, R trivalent metal, A anion (MoO4)2- or (WO4)2-). A group-theoretical analysis of possible transitions is carried out. It is shown that the transitions are of pure ferroelastic nature, occur between centrosymm…
Optical and EPR studies of K(H1−xDx)2PO4 (0⩽x⩽1) single crystals irradiated at 77°K with 60Co gamma rays and observed in liquid nitrogen, argon, and oxygen, have permitted not only the identification of two radical species produced as HPȮ−4 and H2PȮ4, but also a description of the annealing processes and their correla…
Condensation potentials and corresponding electrical currents are observed during the isothermal growth of amorphous, cubic, and hexagonal ice from the vapor phase. Upon heating of the condensate a thermally stimulated current (TSC) spectrum is observed with the application of any external electric field. Current peak…
Metal complexes of water-soluble and other porphyrins have been prepared by a heterogeneous reaction with the metal reactant present in an insoluble form. The oxidation state of the metal is important in the reactions. Metal reactants in the lower oxidation states (0, I, II) react with porphyrins but those in the high…
The generation of periodic surface corrugations by ion-beam milling and chemical etching of grating relief patterns in photoresist is analyzed. A general treatment is developed for gratings of any desired period on substrates of arbitrary reflectivity, but particular emphasis is given to the generation of gratings wit…
Effects due to overlap between orbitals on neighboring atoms and to next-nearest-neighbor interactions, on the electronic structure, are investigated. As an illustration of their importance, analytic results are obtained for the density of states of a Bethe lattice and numerical calculations are carried out to obtain…
Molecular dynamics calculations have been carried out to establish quantitative properties of the Gaussian core model near its crystal–fluid transition. Two densities have been considered, for both of which the stable crystal structure at absolute zero is body-centered cubic. Spontaneous melting and freezing events we…
The Hall mobility has been measured for the first time in a layer compound both along and perpendicular to the layers. The measurements have been extended as a function of temperature and of electrical field by a pulse technique. The results indicate that both mobilities are limited by homopolar optical-phonon scatter…
Th e effect of TiN p articles ill low carbon low allo)' steels 011 the austellite graill size was studied in relation to tlte dissolutioll , coalescence and reprecipitation.Nlain results were as follows.(I) Ostwald ripening was observed in the process of coalescence of TiN jJarticles.( 2) Thg main factors COli trollin…
Single crystals of NiPcI(1.0) (Pc = phthalocyanine), which are composed of one-dimensional stacks of (NiPc)(+0.33) molecules and chains of I(3)(-) molecules, exhibit metallic electrical conductivity in the stacking direction. At room temperature the mean free path of the carrier is 3.3 to 8.2 angstroms.
Photoemission studies combined with measurements of the magnetic susceptibility show that La segregates to the surface of La${\mathrm{Ni}}_{5}$ in the presence of ${\mathrm{O}}_{2}$ or ${\mathrm{H}}_{2}$O, and the Ni precipitations are formed during hydrogenation. This represents a self-restoring mechanism of the acti…
We propose a practical scheme to calculate structural energies in crystalline semiconductors. The method is applied to Si to calculate changes in charge densities and harmonic energies for $\mathrm{TO}(\ensuremath{\Gamma})$, $\mathrm{TA}(X)$, and ${C}_{11}\ensuremath{-}{C}_{12}$ distortions. Cubic anharmonic terms are…
热膨胀系数是金属材料最重要的基本性质之一. 研究金属热膨胀系数的规律性对选择和使用合适的金属材料,在理论上和实践中都有很大的意义. 金属热膨胀系数的规律性,前人曾有不少研究<sup>[1-5]</sup>. 如Carnelley<sup>[1]</sup>早就指出熔点高的材料具有较小的热膨胀系数而熔点低的金属具有较大的热膨胀系数. 后来Hidnert和Sonder<sup>[2]</sup>把这个关系表达成下列经验公式:
The problem of diffusion controlled edge dislocation climb in a cylinder subjected to a biaxial stress state is solved using a finite element method of numerical analysis. The elastic interaction between the vacancy and the dislocation, which depends on both the r and θ coordinates about the dislocation, is included i…
The paper provides a qualitative review of the effects of fast neutron irradiation on the mechanical behavior of materials used in the construction of Fast Breeder Reactor Core Components. The paper is presented in three sections. First, effects of preirradiation on the strength, ductility, elastic moduli, thermal cre…
X-ray photoelectron spectra for the perovskite-type oxides SrCoO 3- x ( x =0.5, 0.25, 0.03) were measured to observe the electron shake-up satellites in Co2p levels. The satellites are considered to be caused by the charge transfer from O2p σ to Co3d e g . Based on the one-electron model, the energy difference between…
The diffraction of scalar waves by two parallel slits in a plane screen is examined by a method which uses orthogonal functions and Fourier transformations. A solution is obtained in the case of a perfectly soft screen. Numerical results of the plane wave transmission coefficients for normal incidence are given for k=…
Observations are reported of the run of TiO band strength (7120 A) with effective temperature for stars at the tip of the giant branch in globular clusters. At temperatures for which the band is strong in field giants, TiO is undetected in clusters of intermediate metallicity. For this result reddening corrections are…
Relative values of thermospheric photoelectron energy distributions between 2 and 100 eV were measured over the altitude range 100–220 km by using a 127° cylindrical electrostatic deflection analyzer flown on a rocket. The measured photoelectron spectra display distinct features that are theoretically predicted (Victo…
The spin configuration was studied by means of magnetic torque measurements on single crystals of manganese substituted orthoferrites, YFe 1- x Mn x O 3 where 0≤ x ≤0.55, at temperatures between 77 K and 450 K. Spin reorientations were observed in the samples containing more than x =0.1. It was concluded that the anti…