Materials Literature
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Anomalous scattering factors Δf′ and Δf″ have been calculated relativistically for Cr, Fe, Cu, Mo, and Ag Kα radiations for the atoms Li through Cf. An interpolation scheme for other wavelengths is included in a separate report. Relativistic calculations of the photoelectric cross section have been made and the integr…
Reflection measurements have been made for the first time on single-domain cholesteric liquid-crystal films. We observed spectral structure and polarization character with obliquely incident light never seen with the previously studied disordered films. We also obtained numerical solutions to Maxwell's equations for o…
Diamond powder is rapidly sintered into molded shapes at a pressure of about 65 kilobars and a temperature of 2500 degrees Kelvin. Other conditions of pressure and temperature are also suitable. The product compares favorably with natural carbonado in its properties.
A method has been developed for the preparation of uniform palladium particles of diameter from 55 to 450 angstroms. Uniform particles of gold layered on palladium were also synthesized. Hydrothermal treatment of aluminum hydroxide sol was used to prepare rods of alumina with uniform cross section from 100 to 500 angs…
The existence of antiferromagnetic order in the monoclinic phase of ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ has been confirmed by a neutron polarization analysis experiment. Conventional neutron-diffraction experiments on powders and single crystals have been performed to determine the magnetic structure. The observation…
The molecular-field description of the isotropic-nematic phase transition in liquid crystals is investigated. It is found that the effects of fluctuations may be observable, and the first corrections due to fluctuations to the light scattering and magnetic birefringence in the isotropic phase are determined. The effec…
We have observed a divergence of the magnetic birefringence, and a critical increase and slowing of the fluctuations in order in the isotropic phase of a nematic liquid crystal. Our results are quantitatively described by a mean-field model except for a critical region close to the ordering temperature where the fluct…
Compounds containing a first-row atom are shown to have an important additional contribution to the nonlinear optical susceptibility ${d}_{\mathrm{ijk}}$. Inclusion of this effect explains the anomalous sign of ${d}_{33}$ for ZnO and leads to excellent agreement with experiment.
The tensile properties of Mo single crystals in six different orientations were investigated over the range from 20 to 550 °K. The plastic behavior shows asymmetry in the critical resolved shear stress for slip on both {110} and {112} planes. At low temperatures, within the thermally activated region, slip takes place…
Reduction of rare-earth (RE) ions to lower valence states in ionic crystals is described in terms of the equilibrium distribution theory for the (alkali halide):RE2+ and (alkaline-earth halide):RE3+ systems. Thermoluminescence glow curves of radiation-reduced CaF2:RE3+ systems reveal that the reoxidation of the divale…
The optical absorption spectrum (4000–17 000 Å) of crystals of Cs2(Mg0.996Ni0.004Cl4)Cl was measured at approximately 5 and 80°K. The host material was found by x-ray diffraction to have the Cs3(CoCl4)Cl structure (I4 / mcm) at temperatures down to at least 10°K. In the solid solution the spectra showed that nickel(II…
The mixing action of two crossed ultrasonic beams has been studied. The theoretical treatment of Taylor and Rollins is extended to include the all-pure-mode cases for the prosess $L ({\ensuremath{\omega}}_{1})\ensuremath{-}T\left\{{{\ensuremath{\omega}}_{2}}{{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}…
Finite ultrasonic velocity changes at the structural phase transition in SrTi${0}_{3}$ are observed for different modes. They are interrelated and correlated by theory. No critical effects are observed.
Heterojunctions of nZnSe–pGe switched from a high impedance to low in 100 nsec when a threshold voltage is exceeded. Resetting occurs in the opposite bias direction in 10 nsec after sufficient current is applied. Either state is maintained with all bias removed for a minimum of two weeks.
A sum rule is constructed which relates the third moment of the imaginary part of the dielectric function at zero wave vector to an integral of the product of the Laplacian of the crystal potential and the fluctuation of the electron density. This sum rule, though rigorous, will be of real use only when the real solid…
All the one-loop graphs of the dual-resonance model are explicity calculated. These graphs fall into three categories:planar, nonorientable, and orientable nonplanar. Using the properties of various elliptic functions, we are able to generalize the renormalization procedure, obtained previously for the planar diagrams…
The preparation and measurement of magnetic properties of cobalt-samarium permanent magnets prepared by liquid-phase sintering are discussed. Energy products in excess of 15×106 G Oe were observed. Long time exposure to air at 150°C did not degrade the samples.
The optical-phonon spectrum of ZnSi${\mathrm{P}}_{2}$ has been investigated by polarized Raman scattering at 6328 \AA{}. The results are compared with phonon modes in related tetrahedrally coordinated compounds and with a set of symmetry coordinates. The low-frequency dielectric constants are estimated from the Lyddan…
It has been suggested that two types of second sound, "drifting" and "driftless," are possible in dielectric crystals. The conditions for the existence of these two types of second sound are obtained, both from a heuristic analysis of the problem and from an exact solution of the complete linearized Boltzmann equation…
High-temperature powder x-ray diffraction photography and differential thermal analysis give 1643 K for the rhombohedral-to-cubic transition temperature of PrAl${\mathrm{O}}_{3}$; for NdAl${\mathrm{O}}_{3}$, this transition temperature is estimated to be 2020 K. The 800 K transition temperature of LaAl${\mathrm{O}}_{3…