Materials Literature
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The authors have examined the magnetic structures of the antiferromagnetic layered compounds Co 1/3 NbS 2 and Co 1/3 TaS 2 using single-crystal neutron photographic and counting methods. The magnetic structure of Co 1/3 NbS 2 has been determined in detail, and has an orthohexagonal unit cell, containing two Co atoms,…
The dielectric dispersion in pure and doped ferroelectric triglycine sulphate (TGS) single crystals is investigated in the frequency range 200 Hz to 100 kHz in both, ferro- and paraelectric phases. The results obtained strongly suggest that the dielectric dispersion and reduction in dielectric loss in doped TGS crysta…
The non-equilibrium state of high-angle grain boundary structure caused by the presence of grain boundary defects of dislocation nature is analysed. Such a state is characterized by the presence of long-range elastic fields of the boundary and/or by mechanical instability of the grain boundary structure. The creation…
The temperature and field dependences of both, drift mobilities and effective free paths of electrons and holes heated by the electric field are investigated. The non-activated hot hole mobility as well as carrier free paths increase with kinetic energy. The highest possible electric field is limited by the avalanche…
Surface and bulk-plasmon satellites for the x-ray photoemission spectra of simple metals have been calculated using the transition-matrix approach. Intensities for photoemission at various depths, ${z}_{0}$, from the surface of the sample are presented. It is found that the singularity at the upper edge of the bulk-pl…
The self-consistent phonon (SCP) theory is used to study the mechanical stability of crystals to vibration as temperature is increased. The temperature at which instability occurs, ${T}_{I}$, depends sensitively on the approximation made to the SCP theory. In the self-consistent harmonic approximation, ${T}_{I}$ is \e…
We extend earlier molecular dynamic calculations to a study of the rheological properties and failure of sodium silicate glass. Under biaxial compressions glass flow and stress relaxation are observed. The simulated glass ‘‘breaks’’ by forming cavities when subjected to a sudden large biaxial expansion. A microscopic…
Stage transformations in the potassium-graphite intercalation compound have been studied by in situ x-ray diffraction. A precise phase diagram has been determined for the stages up to 7. The stage dependence of $\ensuremath{\Delta}\ensuremath{\mu}(n)$, the stable range of a given stage $n$ in chemical potential, is ev…
Epitaxial (Pb, La)(Zr, Ti)O3 thin films were grown successfully on (0001) sapphire substrates at below 600 °C. High quadratic electro-optic coefficient of 0.8×10−16 (m/V)2 was also obtained at 6328 Å. The rf planar magnetron sputtering process improved the quality of the film, which will be suitable for thin-film inte…
We present the parametrization of nitrogen for use in the valence effective Hamiltonian (VEH) technique. We describe five different parametrization schemes and discuss the quality of the results each of them affords. The VEH method is then applied to the study of the electronic structure of nitrogen containing polymer…
Expressions are derived for the sixteen wave front aberration coefficients of a single grating. These give the wave aberrations to the fourth order for a plane symmetric grating system. The contributions from each mirror and grating can be added to give the aberrations in the final image. Problems encountered with int…
We report the polarized Raman spectra of vitreous $^{30}\mathrm{Si}$${\mathrm{O}}_{2}$ and compare the principal frequencies with those of vitreous $^{28}\mathrm{Si}$${\mathrm{O}}_{2}$. This yields the $^{28}\mathrm{Si}$\ensuremath{\rightarrow}$^{30}\mathrm{Si}$ isotopic shifts for nearly all vibrational modes of the…
The temperature dependence of the refractive indices of high-purity fused silica and crystal quartz was measured in the 450-1600 nm wavelength range and at temperatures from room temperature to 400 degrees C. The average thermal coefficients of the refractive indices of those materials show opposite sign. The waveleng…
The core level electrons in iron and its three oxides FeO, Fe 3 O 4 and alpha -Fe 2 O 3 have been studied by means of X-ray photoelectron spectroscopy. The main features of the spectra have been identified and electron binding energies have been measured. The Fe 2p peaks of the oxide spectra are broadened (FWHM approx…
The molecular field theory of nematics is rephrased in density functional language. The free energy in the nematic state is expressed as a functional expansion around the isotropic state in powers of the nematic order parameters P l and the fractional density change eta at the isotropic-nematic transition. The crucial…
The authors present a band calculation for antiferromagnetic MnTe. MnTe is found to be a semiconductor with an indirect energy gap of 0.35 eV. The density of states and reflectivity spectra are presented and compared with experiment. As a result of comparison they conclude that optical properties of MnTe can be descri…
The interactions of tetrakis(4-N-methylpyridyl)-porphine (H2TMpyP-4) and its copper(II), nickel(II), zinc(II), cobalt(III), iron(III), and manganese(III) derivatives with several nucleic acids have been investigated. Spectrophotometric titrations of H2TMpyP-4 and Cu(II)TMpyP-4 with the synthetic polymer poly(dG-dC) co…
A strong case is made to show that the $F$-type color centers in oxide crystals are qualitatively different from the color centers of alkali halides. A semiquantitative discussion is followed by the results of an $X\ensuremath{\alpha}$ self-consistent-field calculation for the $\ensuremath{\alpha}$-${\mathrm{Al}}_{2}$…
Both elastic and inelastic electron scattering have been used to characterize and investigate the electronic properties of As${\mathrm{F}}_{5}$-doped polyparaphenylene. Evidence is presented for the existence of a polaron state slightly above the top of the valence band at low doping levels. An increase in the doping…
The local translational structure of a two-dimensional colloidal liquid is observed by use of cross correlation of the intensity fluctuations of light scattered by the liquid through two different wave vectors. The utility of multidetector scattering in probing multipoint correlations in disordered phases is thereby d…