Materials Literature
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The notion of a perfect crystal in d-dimensional physical space may be generalized to the ``deterministic'' quasicrystal generated by a cut by a d-dimensional ``physical'' plane through a periodic array of (D-d)-dimensional hypersurfaces in a D-dimensional space. (The quasicrystal tilings generated by projection from…
Three regimes of pressure and temperature are identified in which silane pyrolysis has distinctly different initial kinetics: in two regimes the initial reactions are heterogeneous and in the third regime it is homogeneous. We report here a preliminary model for the heterogeneous reaction regime where the decompositio…
Diamond has been obtained by ArF excimer laser-induced chemical vapor deposition. The reaction was carried out by use of C2H2 diluted with H2 as a source gas and at the pressure range of 8–75 Torr. The products were characterized by scanning electron microscopy and reflection electron diffraction. Deposits prepared in…
Mutual-diffusion and tracer-diffusion coefficients, $D$ and ${D}^{*}$, are measured in the miscible polymer blend system polystyrene + poly (2,6-dimethyl-1,4-phenyleneoxide) by forward recoil spectrometry. We find $D$ to be much larger than ${D}^{*}$, an increase that is predicted quantitatively by a theory which incl…
Monte Carlo simulations have been performed on a diamond lattice model of semiflexible polymers for a range of flexibilities and a range of chain lengths from 50 to 800 segments. The model includes both repulsive (excluded volume) and attractive segment–segment interactions. It is shown that the polymers group into tw…
Saffman-Taylor experiments are conducted in a circular axisymmetric Hele-Shaw cell. We show that when a small pre-existent isolated bubble comes into contact with the tip of a finger, this finger starts growing faster, its radius of curvature at the extremity is reduced, and it takes a parabolic shape. When its veloci…
Realistic ab initio total-energy calculations are performed to investigate the electronic and geometric structure of crystalline ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$. Results include the following: total energies for various distortions, the equilibrium geometric structure, intralayer and interlayer cohesive energie…
I define a hopping Hamiltonian for independent electrons on a two-dimensional, infinite, quasiperiodic Penrose lattice with a particular on-site potential, depending upon a parameter r. I then find the exact ground-state wave function for this Hamiltonian. The wave function is shown numerically to have a power-law dec…
We define a one-parameter family of hopping Hamiltonians with an on-site potential, for independent electrons on a two-dimensional quasiperiodic Penrose lattice. The resulting models include the vibrational modes of the lattice. This problem is then investigated numerically---exploiting the symmetries of the model inc…
The method of molecular-dynamics simulation for an assembly of 6480 soft spheres is used to investigate the layerwise structure of a {111} solid-liquid interface for an fcc crystal. A heterogeneous two-phase structure in each layer is suggested by a 2D Voronoi polygonal analysis but this is not supported by various or…
The structural environment of Bi incorporated in Ge chalcogenide glasses has been found from extended x-ray absorption fine-structure data to consist of threefold coordination. An increase by a factor of 2 in the Debye-Waller factor occurs as the carrier type changes from $p$ to $n$. A mechanism involving the suppress…
A new method for calculating the effect of stacking faults on x-ray and neutron-diffraction patterns is developed. Using a computer-generated, statistically faulted crystal model, we show that it is possible to examine the effect of various types of faults in different lattice types from a simple and unified point of…
A new electro-optical material based on nematic liquid crystal dispersed in a polymer matrix has recently been introduced by Fergason. This technology (termed NCAP, for nematic curvilinear aligned phase) is suitable for making very large area (thousands of square centimeter) light valves and displays. The device consi…
The thermoluminescence (TL) of LiF (TLD-100) has been studied over the temperature range 90 to 300K. A total of nine glow peaks are observed in this temperature interval. The most intense peak is the one at 137K. Besides this, three other peaks at 149, 254 and 275K are well resolved and their growth with exposure coul…
The authors establish rigorously the relationship between the growth constant of uniform trees with two branch points and that of self-avoiding walks. For combs, they estimate the corresponding exponent and study the mean-square lengths of the internal and external branches.
The mean square displacement (MSDS) of the ions in the perovskite KZnF 3 have been derived from neutron scattering measurements between 4 and 1073K. The results are compared with the values calculated in the quasi-harmonic approximation. In the high-temperature regime, only a slight increase of F - -ion anharmonicity…
Abstract With the aim to investigate the influence of structural isomerism on the mesomorphic thermal stability in main chain thermotropic polycondensates, a series of poly(azomethines) and low molecular weight models have been prepared. The model compounds exhibit smectic and/or nematic mesophases whose stabilites ar…
The authors have attempted to provide a relatively brief outline of the current situation regarding the formation and properties of charge density wave states in low-dimensional transition metal compounds. They have chosen to illustrate the types of problem involved by specifically focusing on 1T- and 2H-TaS 2 and TaS…
Abstract The B' localized mode, infrared absorption peak (which is due to {100} platelets) and its relations with other features in the infrared absorption spectrum of type la diamonds have been investigated. It is recognized that it is possible, on the basis of their one-phonon infrared absorption spectra, to separat…
We discuss the electromagnetic scattering of a plane wave by an axionic domain wall, under an arbitrary incident angle. We estimate the reflection coefficient which depends on the plane wave frequency and angle and take always a very small value. The two independent circular polarizations propagate with different velo…