Materials Literature
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A deep-defect level in a semiconductor is simulated by a cluster of host atoms surrounding the defect. The system is then treated as a "large molecule," the energy levels and wave functions for the entire cluster being obtained using molecular-orbital techniques. As examples, the substitutional nitrogen-atom impurity…
The amino acid L-tyrosine (C9H11NO3) and its salt L-tyrosine hydrochloride (C9H11NO3·HCl) crystallize respectively in the space groups P212121, a=6.913(3) Å, b=21.118(10) Å, c=5.832(3) Å, and P21, a=11.083(5) Å, b=9.041(4) Å, c=5.099(3) Å, β=91.82(3) Å. Both structures have been refined by neutron diffraction techniqu…
Dispersion curves for lattice vibrations propagating along the five major symmetry directions in a single crystal of rubidium have been measured using inelastic neutron scattering. Care has been taken to identify spurious peaks in the neutron groups and to correct for effects of instrumental resolution. The results, a…
We have been able to extend the dielectric theory of ionicity to include such $d$-electron systems as the noble-metal halides (e.g., CuCl, AgBr, etc.), $AB$ transition-metal compounds (e.g., ScN, MnS, FeO, NiO, etc.), ${A}_{m}{B}_{n}$ crystals (e.g., Zr${\mathrm{F}}_{4}$, Ti${\mathrm{O}}_{2}$, ${\mathrm{Cr}}_{2}$${\ma…
A simple localized-bond-charge model for the calculation of nonlinear optical susceptibilities is presented. We find that there are three important contributions to the nonlinearity, namely, the bond ionicity, the difference in atomic radii of the bonded atoms, and $d$-electron contributions. By including these effect…
The small signal Raman gain in a single-mode glass waveguide amplifier has been measured directly. The measured gain is in good agreement with that calculated from the Raman cross section. The cross section was determined by a comparison of the spontaneous Raman scattering of fused quartz and benzene.
The isobaric temperature dependence of the low frequency dielectric response of KTaO 3 and SrTiO 3 is reported for the range 2-300 K together with its isothermal pressure dependence for hydrostatic pressures up to 12 kbar in the range 77-300 K. The results are used to show that the paraelectric phase of these material…
The electro-optic properties of a new room-temperature positive-dielectric-anisotropy nematic liquid crystal are described. Devices based on the twisted nematic and phase-change effects are shown to operate at very low voltages.
Abstract A direct electron microscope study has been made of defect clusters produced in alkali halides by ionizing radiation. A technique has been developed for preparing foils of alkali halide crystals less than a few hundred nanometres thick for observation in the microscope, and a liquid helium cooled stage allows…
The infrared spectra of lithium isocyanide and of sodium and potassium cyanides in the solid phase were examined over the range 4000 to 140 cm −1 at room temperature. A study of the effect of cooling the solids to liquid nitrogen temperature has been carried out.
On the basis of polarization arguments, the equality τd=τl is proposed as the critical condition for the threshold point of chalcogenide glass switches, τd being the dielectric relaxation time and τl the carrier lifetime. It is shown that this switching criterion is in good agreement with measurements and that it expl…
Abstract Das Mössbauer‐Spektrum von 119 Sn in Sn 2 O 3 zeigt, daß in dieser Verbindung zwei‐ und vierwertiges Zinn vorliegen. Die verhältnismäßig große Quadrupolaufspaltung des Zinn(II) weist auf eine niedrige Symmetrie der ersten Koordinationssphäre hin, während sich Zinn(IV) in ähnlicher Umgebung wie im SnO 2 befind…
It is shown that the electric-field-induced cholesteric-nematic phase transition of mixed liquid crystal possesses two important properties; (i) a sharp threshold in the scattering- vs. -voltage characteristic and (ii) an electrically controllable relaxation time. The mixed liquid crystal is composed of p- n -butoxybe…
The general problem of which insulator configuration is best for gas-insulated systems is considered. A smooth disc is compared with both a corrugated disc and a cone and the cone is seen to have considerable potential. Impulse and switching surge voltages are more severe than 60 Hz when contamination is present on th…
The shear moduli, C44 and C55, and the temperature dependence have been computed for the orthorhombic unit cell of paraffinic hydrocarbons. The computations were conducted by expressing the shear moduli in terms of intermolecular interactions formulated for infinitely long rows of H…H force centers. The interaction pa…
A dislocation distribution is initially in equilibrium, piled up against a block by a uniform applied stress. The block is removed and the subsequent motion of the distribution, for a linear stress—velocity law, is analysed by the complex representation introduced in Parts I to V of this study of dislocation group dyn…
The $4{f}^{14}\ensuremath{\rightarrow}4{f}^{13}5d$ absorption spectrum of an ${\mathrm{Yb}}^{2+}$ ion in cubic crystals is demonstrated to have four peaks, which correspond to the four $5d ({e}_{g} or {t}_{2g}) 4{f}^{13}(^{2}F_{\frac{7}{2}} or ^{2}F_{\frac{5}{2}})$ final states.
Abstract In order critically to evaluate the previous morphological interpretations of stress relaxation during oriented crystallization, a reexamination was made of the relaxation behavior of the same oriented natural rubber material used for the x‐ray investigation in Part II of this series. Our results were found t…
Air oxidation of (U, Pu)O 2 solid solutions having Pu/(U+Pu) ratios of 0.2 and 0.25 was studied using a recording thermal balance. For Pu/(U+Pu)=0.2, the original fluorite MO 2 phase oxidized first to tetragonal M 3 O 7 ; further oxidation at 450°C< T <600°C gave a two‐phase mixture of M' 3 O 8 and a cubic phase…
The absorption spectrum of thin films of CfCl3 was measured at 298, 77, and 4°K in the range 6000–46 000 cm−1. Interpretation of the results was based on systematic variation of energy level parameters over the actinide series. Electrostatic, spin-orbit, and configuration interaction terms were calculated by diagonali…