Materials Literature
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Using a first-principles approach, we calculate Raman spectra for a model structure of vitreous silica. We develop a perturbational method for calculating the dielectric tensor in an ultrasoft pseudopotential scheme and obtain Raman coupling tensors by finite differences with respect to atomic displacements. For frequ…
A ferroelectric crystal $[4\ensuremath{-}{\mathrm{NH}}_{2}{\mathrm{C}}_{5}{\mathrm{H}}_{4}\mathrm{NH}][{\mathrm{SbCl}}_{4}]$ has been synthesized. The x-ray diffraction studies indicate that it is made of polyanionic chains of $({\mathrm{SbCl}}_{4}^{\ensuremath{-}}{)}_{n}$ forming a tunnel-like structure and the 4-ami…
Several papers pertaining to the design and modeling of high-frequency transformer windings are reviewed. Each paper is summarized, stressing its significant contributions and its relationship to the others. The emphases and relative merits of each are discussed, and the understandability and applicability are evaluat…
First-principles calculations are used to calculate the strain dependencies of the binding and diffusion-activation energies for Ge adatoms on both Si(001) and Ge(001) surfaces. Our calculations reveal that the binding and activation energies on a strained Ge(001) surface increase and decrease, respectively, by 0.21 e…
Electron-hole correlation in quantum-dot quantum wells (QDQW's) is investigated by incorporating Coulomb and exchange interactions into an empirical tight-binding model. Sufficient electron and hole single-particle states close to the band edge are included in the configuration to achieve convergence of the first spin…
We carry out large scale {\sl ab initio} calculations of Raman scattering activities and Raman-active frequencies (RAFs) in ${\rm C}_{48}{\rm N}_{12}$ aza-fullerene. The results are compared with those of ${\rm C}_{60}$. Twenty-nine non-degenerate polarized and 29 doubly-degenerate unpolarized RAFs are predicted for $…
An asymptotic analysis of the Gunn effect in two-dimensional samples of bulk n-GaAs with circular contacts is presented. A moving pulse far from contacts is approximated by a moving free boundary separating regions where the electric potential solves a Laplace equation with subsidiary boundary conditions. The dynamica…
In this work, we perform first-principles calculations of the structural, electronic, vibrational and magnetic properties of a novel ${\rm C}_{48}{\rm N}_{12}$ azafullerene. Full geometrical optimization shows that ${\rm C}_{48}{\rm N}_{12}$ is characterized by several distinguishing features: only one nitrogen atom p…
We have studied the magnetic-field and concentration dependences of the magnetizations of the hole and Mn subsystems in diluted ferromagnetic semiconductor Ga_{1-x}Mn_xAs. A mean-field approximation to the hole-mediated interaction is used, in which the hole concentration p(x) is parametrized in terms of a fitting (of…
We study the structural, electronic, vibrational and magnetic properties of a novel ${\rm C}_{48}{\rm N}_{12}$ aza-fullerene using density functional theory and restricted Hartree-Fock theory. Optimized geometries and total energy of this fullerene have been calculated. We find that for ${\rm C}_{48}{\rm N}_{12}$ the…
Results of ab initio calculations using the relativistic Local Spin Density theory are presented for the magnetic moments of periodic 5d and 4d transition metal interfaces with bcc Fe(001). In this systematic study we calculated the layer-resolved spin and orbital magnetic moments over the entire series. For the Fe/W(…
We report in situ Atomic Force Microscopy experiments which reveal the presence of nanoscale damage cavities ahead of a stress-corrosion crack tip in glass. Their presence might explain the departure from linear elasticity observed in the vicinity of a crack tip in glass. Such a ductile fracture mechanism, widely obse…
Primary and secondary aliphatic alcohols are smoothly oxidised by air to the corresponding carbonyl derivatives with high selectivity using 1% Au on silica.
The systematic in the 4f n → 4f n −1 5d transition energy of divalent lanthanides in inorganic compounds has been studied. Energies were derived from excitation and optical absorption spectra gathered from the literature. Going through the lanthanide series from La 2+ to Yb 2+ , a characteristic variation is observed…
Voltammetric characterization of new types of electrochemical sensors, based on diamond paste, was performed for Fe(III). The construction of electrodes was done using monocrystalline diamond [natural diamond 1 µ, synthetic diamond 50 µ (synthetic‐1), and synthetic diamond 1 µ (synthetic‐2)] powder and paraffin oil. D…
Absorption spectral studies on lanthanides are described, dealing with 4f–4f transitions as structural probe in chemical and biochemical reactions, and compositional dependence of intensity parameters in order to understand the structure and nature of lanthanide bimolecular interaction. This review is basically addres…
The broadband dielectric spectroscopy (10−3–106 Hz) is used to study the effect of stress-strain cycles on the dielectric properties of butyl rubber vulcanizates filled with silica. The influence of chemical modification of the surface of the silica by silane coupling agent (Si69) also was investigated. In addition Tr…
The chiral conducting polyaniline (PANI) nanocomposites [polyacrylic acid/polyaniline/(−) camphorsulphonic acid (CSA)] were synthesized using enzyme, horseradish peroxidase (HRP) in the aqueous buffer solution at pH 4.3. It appears that the enzyme HRP apart being a biocatalyst, plays an important role during the polym…
Polyacrylamide/guar gum (PAam/GG) adduct was prepared by polymerization of a highly concentrated solution of acrylamide (Aam) in the presence of guar gum (GG) by using ammonium persulfate initiator. The adduct was used as a thickener for reactive printing of wool and nylon‐6 under different conditions, including thick…
Polyepichlorohydrin (PECH)/organically modified montmorillonite (OMMT) nanocomposites were prepared by using dichloromethane (DCM) as a cosolvent for both polymer and clay at room temperature, through the solvent-casting method. X-ray diffraction (XRD) was used to confirm the formation of nanoscale polymer/OMMT nanoco…