Materials Literature
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The orientational optical nonlinearity of the mesophases of liquid crystals (LCs) is attracting ever more attention, owing to the high values of the constants characterizing it, owing to the many interesting specific features that LCs introduce even into traditional nonlinear optical effects, and owing to the potentia…
Calculated volumes of formation for substitutional impurities in alkali halides are shown to be approximately consistent with the empirical rule that for miscible crystals the average volume per ion pair scales linearly between the two single-component extremes (Vegard's rule). The small deviations found from the rule…
We present the first experimental study of shear-flow--induced behavior in a two-dimensional anisotropic fluid: circular, freely suspended films of smectic-C liquid crystals. Depending on the topology of the in-plane director configuration, we observe either a phase winding state, where \ensuremath{\Phi}, the phase de…
Silver cluster ions (${\mathrm{Ag}}_{1}$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_{3}$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_{4}$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_{5}$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_{7}$${\mathrm{}}^{+}$, and ${\mathrm{Ag}}_{9}$${\mathrm{}}^{+}$) generated in a sputtering arrangement were filtered in energy sele…
Proton spin-lattice relaxation times (${T}_{1}$) measured for the first time across a random transition-metal alloy system, ${\mathrm{V}}_{\mathrm{x}}$${\mathrm{Nb}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{H}}_{0.2}$, from 100 to 700 K reveal (a) a suppression of hydride phase precipitation at low temperatures…
The growth of nematic films near a wall close to the nematic-isotropic transition is studied for planar boundary conditions. If the nematic phase wets the wall, near the onset of bulk nematic behavior the nematic film near the wall is in a Kosterlitz-Thouless low-temperature phase. The transition to this phase can be…
We show that the \ensuremath{\alpha}-(AlMnSi) crystal structure is closely (and systematically) related to that of the icosahedral Al-Mn-Si alloys. Using a modification of the ``projection'' method of generating icosahedral structures from six-dimensional lattices, we find a simple description of the \ensuremath{\alph…
The dielectric permittivity and loss of 1-cyanoadamantane have been measured under isothermal conditions in the frequency range, 100-2*10 5 Hz and the temperature range, 80-350K in the glassy crystal, supercooled (metastable) and stable (disordered) crystals and partially ordered crystalline states. Two relaxation reg…
X-ray measurements performed on a variety of materials demonstrate that it is possible to observe diffuse scattering that originates in the abrupt change of density at a crystal surface. Such a discontinuity gives rise, in general, to rods of scattering in reciprocal space which are most intense close to the Bragg pea…
A model of intercalation is presented which can be used for sophisticated three-dimensional computer simulations of staging kinetics. A realistic microscopic description of the intercalation process and of the stage-3 to stage-2 transition has been obtained for the first time. Stage disorder and three-dimensional effe…
Field-assisted ion exchange has been used to extend the profile repertoire and to speed the ion exchange process for gradient-index (GRIN) applications. Profiles are predicted for various ion mobility ratios and time-varying electric fields. Profile control is demonstrated by silver for sodium exchange in an aluminosi…
A set of MS-Xα calculations on the MoFe3S4 (SH)3−6 ion is reported. Three levels of theoretical models are considered: spin-restricted, C3v symmetry, which is most easily compared with the traditional ligand-field picture; spin-polarized, C3v symmetry; and spin-polarized, Cs symmetry. An MS=3/2 ground state correspond…
The results of refractive-index measurements in ZrF4–BaF2–LaF3–AlF3 glass and the effects of the addition of NaF are described. The dispersion properties are not enhanced by the addition of NaF, as shown by increased material dispersion M at long wavelengths and decreased crossover wavelength λ0.
A model has been developed which predicts the chromatic properties of gradient-index materials based on the composition of the glass. It yields a gradient Abbe number and a gradient partial dispersion which can be used by the lens designer in the design of achromatic gradient-index lens systems. Over 100 glasses with…
Within a new theoretical approach the current and energy decay in amorphous semiconductors is studied. The relaxation of photoexcited carriers observed by transient photoconductivity experiments in amorphous silicon and chalcogenides can well be described by an algebraic power-law decay. The theoretical explanation is…
The intensity and energy shift of the Ge 3d surface core-level photoemission is determined with the use of synchrotron radiation. Cl- and Br-terminated Ge(111)?(hy(1\ifmmode\times\else\texttimes\fi{}1) surfaces are used to calibrate the absolute coverage CTHETA and to obtain accurate line shapes. We find binding-energ…
The adsorption of chlorine on Si(111)-(7\ifmmode\times\else\texttimes\fi{}7) has been studied with various photoemission techniques with the use of synchrotron radiation. At room temperature, bonding of one, two, and three chlorine atoms to a Si surface atom was observed with Si 2p core-level shifts of 930, 1830, and…
The problem of localization of phonons in disordered materials is studied in the framework of the weak-localization theory. Quantum correction to phonon diffusion is calculated by the resummation technique of maximally crossed diagrams in two and three dimensions. The strong energy dependence of the elastic mean free…
The structure of molecular beam deposited microcrystalline silicon and germanium films prepared under different growth conditions has been analyzed by conventional transmission electron microscope (TEM) and Raman scattering (RS) and compared to electrical conductivity experiments. The TEM measurements yield an average…
Optical absorption spectra corresponding to the 4 A 2 g → 2 E g transition of Cr 3+ in RCrO 3 (R=Er, Ho, Dy and Tb) were investigated. The exciton lines ( R ) with Davydov splitting, and an electric dipole band ( R ') at lower energy side were observed in all compounds. From the temperature and external magnetic field…