Materials Literature
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It is proposed that a molten alloy may contain a 104-atom cluster with icosahedral symmetry and largely icosahedral packing. The cluster may be described as involving twenty interpenetrating Friauf polyhedra. On rapid freezing these clusters form cubic crystals related to the \ensuremath{\beta}-W structure. The struct…
Molecular dynamics was used to refine macromolecular structures by incorporating the difference between the observed crystallographic structure factor amplitude and that calculated from an assumed atomic model into the total energy of the system. The method has a radius of convergence that is larger than that of conve…
The recently discovered order-disorder transformations in pseudobinary semiconductor alloys AxB1−xC are shown to belong to a broader class of such transformations in AnB4−nC4 semiconducting compounds (e.g., chalcopyrites, for n=2). Strain energy, set up by the atomic size mismatch between the A–C and B–C bonds, is sho…
An experiment is performed in which a topological line defect (S=-(1/2)) is forced to move with constant speed c under the action of an applied voltage V. We argue that the line speed is determined by a competition between the viscous damping and the free energy that the system gains by displacing the line, so that c=…
Impurity-dopant effects on grain-boundary cohesion have been studied in a first-principles local spin-density atomic-cluster model of octahedral hole sites in nickel. Rigorous calculations of the total energy and gradient forces on the host atoms show that boron (an enhancer of cohesion) increases the maximum sustaina…
A quasi two-dimensional open Fermi surface with perfect nesting in the third direction is unstable in a magnetic field, versus the formation of density wave phases with quantized wave vectors. We prove that, within the same theoretical model, the Hall conductivity is exactly quantized at zero temperature in each field…
The distributions of activation energies for electromigration damage in Al and Al-4%Cu thin-film interconnects were determined using temperature-ramp resistance analysis to characterize electromigration. The activation energies for the pure aluminum conductors are well represented by a normal distribution. It is noted…
The results of a powder neutron diffraction study of the cubic fluorite solid solution U 1- x Np x O 2 ( x = 0.25, x = 0.75) are presented. For x = 0.25, an antiferromagnetic type- I order appears below T N = (16.5 ± 0.2) K with an ordered magnetic moment μ = (1.8 ± 0.1)μ B . For x = 0.75 the solid solution is magneti…
We derive the generating functional of thermal Green's functions for an interacting electron-phonon system through the use of functional integrals in holomorphic representations (c numbers for phonons and Grassmann numbers for electrons). These integrals are over paths obeying one-sided boundary conditions at either 0…
Amorphous GeTe 2 films with the thickness ∼ 0.5 µm, prepared by sputtering technique, transform into the crystalline GeTe 2 films with the isomorphic structure to β-cristobalite, cubic SiO 2 , at T a (annealing temperature)=200°C. The cubic phase of GeTe 2 is metastable and decomposes into the mixed crystal of GeTe an…
We examine the effect of thin (1--2 monolayers) overlayers of the low-electronegativity metals Cs and Na upon the oxidation of Si(111) surfaces. Synchrotron-radiation photoemission studies of oxygen chemisorption as a function of overlayer thickness and oxygen exposure indicate large oxidation-promotion effects and th…
A comparative study of the electronic structures and conduction properties of the three heterocyclic polymers polypyrrole, polythiophene, and polyfuran has been carried out using the results of ab initio crystal orbital calculations. Important electronic properties such as band gap, bandwidths, ionization potential, a…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOptical Isomer Separation by Liquid ChromatographyDaniel W. ArmstrongCite this: Anal. Chem. 1987, 59, 2, 84A–91APublication Date (Print):January 15, 1987Publication History Published online30 May 2012Published inissue 15 January 1987https://pubs.acs.org/doi/10.1021/ac00129a7…
In this paper a one-dimensional analysis is presented that leads to the appropriate equation of motion for the undeformed portion of a plastic, rigid rod after impact with a rigid anvil. This equation is used as a basis for deducing material properties of the rod material from post-test measurements.
An energetic study of the excitation spectrum in doped polythiophene is presented within the framework of the H\"uckel approximation. The calculations show that localized states like polarons and bipolarons are produced by doping, the formation of doubly charged bipolarons being energetically more favorable than the f…
New expressions are presented, simplified, and discussed for the small-signal-frequency response of systems involving distributions of activation energies with either exponential or Gaussian probability densities. The results involve the possibility of separate but related thermal activation of energy-storage and ener…
The electronic properties of a tight-binding model which possesses two types of hopping matrix element (or on-site energy) arranged in a Fibonacci sequence are studied. The wave functions are either self-similar (fractal) or chaotic and show ``critical'' (or ``exotic'') behavior. Scaling analysis for the self-similar…
The inelastic electron mean free path as a function of energy is calculated for Cu, Ag, Au, and Al. The calculations are based on a model dielectric function \ensuremath{\epsilon}(q,\ensuremath{\omega}), which is obtained from a modification of the statistical approximation. In this approach \ensuremath{\epsilon}(0,\e…
Te-Ge-Sn-Au thin films were studied for phase change type rewritable disk media, in order to obtain the fast crystallization speed and the thermal stability. Films were prepared by co-evaporation method. It was found that through static record/erase measurements the threshold crystallizing pulse duration of Te60Ge4Snl…
Any desired surface wettability of a plastic surface can be produced by changing the concentration of the plasma gas, which here is a mixture of oxygen and a compound which includes fluorine. In the plasma treatment, the use of a third electrode consisting of a metal mesh for ion trapping can significantly decrease th…