Materials Literature
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We have investigated Pd nanowires theoretically, and found that, unlike either metallic or free atomic Pd, they exhibit Hund's rule magnetism. In long, monoatomic wires, we find a spin moment of 0.7 Bohr magnetons per atom, whereas for short, monoatomic wires between bulk leads, the predicted moment is about 0.3 Bohr…
We investigate the band structure of electrons bound on periodic curved surfaces. We have formulated Schrödinger's equation with the Weierstrass representation when the surface is minimal, which is numerically solved. Bands and the Bloch wavefunctions are basically determined by the way in which the ``pipes'' are conn…
We propose a theory of the origin of transport nonuniversality in disordered insulating-conducting compounds based on the interplay between microstructure and tunneling processes between metallic grains dispersed in the insulating host. We show that if the metallic phase is arranged in quasi-one-dimensional chains of…
We report studies of polycrystalline samples of the metallic ferromagnet ${\mathrm{Pr}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{CoO}}_{3}$ through measurements of the magnetization, ac magnetic susceptibility, resistivity, and specific heat. We find an unusual anomaly around ${T}_{A}=120\mathrm{K},$ much below the ferromagne…
We construct a diffuse-interface model of two-phase solidification that quantitatively reproduces the classic free boundary problem on solid-liquid interfaces in the thin-interface limit. Convergence tests and comparisons with boundary integral simulations of eutectic growth show good accuracy for steady-state lamella…
It is found that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. A strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing indirect evidence of the coherent microwave radiation by the crystals. A similar depend…
First-principles pseudopotential density functional calculations are reported for hydrogen- and oxygen-related defects in crystalline pentacene $({\mathrm{C}}_{22}{\mathrm{H}}_{14}).$ It is shown that defects that perturb a carbon atom so as to remove its ${p}_{z}$ orbital from participation in the \ensuremath{\pi} sy…
The electronic structure of noble-gas solids is calculated within density functional theory's exact-exchange method (EXX) and compared with the results from the local-density approximation (LDA). It is shown that the EXX method does not reproduce the fundamental energy gaps as well as has been reported for semiconduct…
Three problems are considered in which inhomogeneous broadening can yield unusual consequences. One problem involves the energy levels of atoms moving within nanopores of nearly cylindrical cross section. A second involves atomic or molecular motion in a quasi-one dimensional interstitial channel within a bundle of ca…
New families of carbon single-walled nanotubes are proposed and their electronic structures are investigated. These nanotubes, called graphynes, result from the elongation of covalent interconnections of graphite-based nanotubes by the introduction of yne groups. Analogously to ordinary nanotubes, armchair, zigzag, an…
Current flow, considering a semiclassical electron--electric-field interaction and electron scattering by acoustic phonons, is studied in semiconducting zig-zag carbon nanotubes. The $\ensuremath{\pi}$-electronic band structure and the phonon spectrum of the nanotube are both calculated from graphene by the zone-foldi…
A method has been developed for visualizing the internal deformation fields in opaque materials during impact events using a combination of flash X-rays and digital speckle analysis. The random speckle pattern required for the digital speckle analysis is achieved by seeding the specimen with a layer of 20% coverage X-…
Focused ion beam (FIB) milling offers a novel approach to preparation of site-specific cross-sections of heterogeneous catalysts for examination in the transmission electron microscope (TEM). Electron-transparent sections can be obtained without the need to embed or grind the original sample. Because the specimen can…
This work reports the first experimental study of the cyanoacetic acid (CAA) monomer. Samples of CAA were isolated in low-temperature argon, krypton, and xenon matrixes and characterized using FTIR spectroscopy. Annealing experiments revealed the presence of different conformers in the matrixes. The direct interconver…
The problem of finding the bivariate chain length ( n )/number of branch points ( N ) distribution for polyethylene produced by a mixed metallocene catalyst system in continuous (CSTR) and semibatch reactors is addressed in two ways. The first uses distinct classes of chains with a certain number of branches, the seco…
d -Sorbitol spherulites developed concentric rings in response to changes of crystallization temperature. Unlike extinction rings of polymer spherulites, these growth rings were linked to the concomitant crystallization of polymorphs (E and E‘) in temperature-dependent ratios. The growth rings provided a convenient wa…
T he American Society for Quality (ASQ) is a professional association dedicated to advancing quality concepts in such industries as manufacturing, service, health care, and government.Its vision is to make quality a global priority, an organizational imperative, and a personal ethic, as well as to become the community…
Abstract Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound wil have poor dispersion of the filler and a poor cure characteristic. Improvement of properties of silica‐filled styrene‐butadiene rubber (SBR) compounds has been studied using emulsion SBR‐based a…
Nodal admittance matrix models are obtained for wye-connected three-phase transformers with various grounding impedance configurations. The derivations have been performed using computational symbolic algebra, avoiding the necessity for simplifying assumptions. An original model for the general case of a wye-wye trans…
Smooth and nonswelling spherical silica particles with a diameter of 100 nm and an aminopropyl coating are soluble in water at pH 11, coagulate quickly at pH 3, and redissolve at pH 9. Electron microscopy as well as visible spectra of covalently attached porphyrins indicate the aggregation state of the particles. Long…