Materials Literature
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We re-examine the charge longitudinal response, as measured in inelastic electron scattering, within the framework of a semi-classical RPA theory, utilizing a Skyrme force. The effects of the Hartree-Fock field are analysed. A comparison with an exact RPA calculation is presented.
Ag [C 3 H 6 NO 2 ] cristallise dans le systeme monoclinique avec le groupe d'espace P2 1 . Affinement de la structure jusqu'a 0,025. Les ions Ag I presentent une coordination digonale. Chaque ion Ag I est lie a un atome O (carboxylique) et a l'atome N (amine) de deux molecules d'alanine differentes pour former des cha…
Polycrystalline potassium samples have been plastically deformed under tension and the resulting effects on the phonon conductivity and phonon-drag thermopower have been investigated. The reduction of the lattice thermal conductivity ${\ensuremath{\lambda}}_{g}$ due to dislocations is much larger than can be explained…
Thin (<5 nm) air-oxidized Cr layers are deposited on the alumina output windows of radio-frequency klystron tubes to prevent electron multipactor by reducing the secondary electron emission yield of the alumina surface. The top several nanometers of these layers appear to be Cr2O3. To compare the measured surfa…
We have examined the angular distributions of medium-energy (500--1500 eV) elastically backscattered electrons from bulk Cu(001) and Ni(001) crystals and from pseudomorphic Cu on Ni(001). The observed diffraction features are largely governed by forward scattering of the outgoing electrons, and incoming beam scatterin…
An ${\mathrm{sp}}^{3}$ model for ZnS is constructed and validated by comparison with optical absorption and photoemission data. It is used to predict the atomic and electronic structure of three cleavage surfaces of ZnS, zinc blende (110), and wurtzite (101\ifmmode\bar\else\textasciimacron\fi{}0) and (112\ifmmode\bar\…
The properties of monolayer and multilayer deposits of ${\mathrm{N}}_{2}$ on graphite are calculated using a pattern optimization of the total lattice energy and a Monte Carlo procedure with continuously deformable periodic boundary conditions. It is confirmed that the monolayer ground state is a 2 \ensuremath{\surd}3…
The frequencies of several zone-center vibrational modes in graphite have been calculated from first principles, with results in very good agreement with experiment. By studying the effect of charge transfer and lattice-constant change on ${E}_{2g}$-mode frequencies, we find that the systematic stage dependences of bo…
The UV–visible spectrum of 200 nm thick films of poly(p-phenylene vinylene) (PPV) shows three absorption bands, with maxima at 6.12, 5.06, and 3.09 eV. The first two absorption bands are related to localized molecular states while the band at 3.08 eV has a more complicated character with a 1.5 eV bandwidth, a 2.49 eV…
AlPO 4 cristallise dans le systeme hexagonal avec le groupe d'espace P6cc pour Al et P ordonnes, mais affine jusqu'a 1,9% dans le groupe d'espace P6/mcc pour Al et P desordonnes
Polarization-dependent absorption coefficients of various molecular vibrational bands (i.e., IR markers) in the 2.5-20-microm spectral region were measured for two nematic liquid crystals (LCs), 5CB and MBBA. Combining the measured absorption dichroism of a dipole moment with a correction factor g, which takes the ani…
The equilibrium lattice parameters, bulk modulus, shear elastic constant ${C}_{44}$, and cohesive energy of GeTe are calculated with use of the ab initio scalar relativistic pseudopotential in the local-density approximation. The convergence of the structural properties in basis-set size and Brillouin-zone averaging i…
The first-order phase transitions among the hydration states in both Na and Ca vermiculites are studied by water-adsorption isotherm and specific-heat measurements. These compounds have three kinds of hydration states defined by the number of water layers in the interlamellar space between the silicate layers (0-, 1-,…
We have performed restricted Hartree-Fock self-consistent-field calculations on BeO and MgO clusters embedded in a point-charge field (chosen to represent the Madelung field in BeO and MgO crystals) in order to understand better the role of the many contributory shifts to the ionization potentials which occur for atom…
Acoustic-phonon transmission through a realistic Fibonacci superlattice is studied theoretically. We find a number of transmission dips corresponding to Bragg-like reflections of phonons. The transmission spectrum is much more complex than in the periodic case; however, the strongest dips in transmission are remarkabl…
X-ray diffraction measurements up to momentum transfer q=16 Å−1 were performed at atmospheric pressure on both the high-density form of amorphous ice obtained by pressurization of crystalline ice Ih at 77 K up to 2 GPa and the low-density form obtained by further heating. These two amorphous phases exhibit significant…
Within the framework of a one-dimensional continuous Ginzburg-Landau theory, pulselike solitary waves in shape-memory alloys are investigated. By neglecting heat conduction, internal friction, and external volume forces, but including shear-strain and strain-gradient contributions in addition to the Landau internal en…
The effects of In impurity on the dynamic behavior of dislocations in GaAs crystals are investigated in comparison with those of Si impurity. Indium, even at a concentration of the order of 1020 cm−3, is found to affect the velocity of moving dislocations only slightly while Si impurity at a concentration of the order…
Dielectric relaxation measurements covering a wide frequency range extending from 10−6 to 106 Hz were made on poly(vinyl acetate) with conventional glass transition temperature Tg of 31 °C at temperatures between 26.85 and 84.77 °C. It was found that temperature dependence of frequency of the maximum dielectric loss b…
This paper describes analyses and confirming experiments on the optimum temperature for fast response in nematic liquid crystal (LC) modulators. It is demonstrated that the LCs or LC mixtures with higher nematic-isotropic phase transition temperatures have higher optimum temperatures and greater potential for improvin…