Materials Literature
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The validity of simpler additive models, accounting for nonlinear optical properties of van der Waals crystals in terms of independent molecular contributions is questionable in the case of more associated molecular structures such as examplified by the hydrogen-bonded crystal lattice of urea. A number of one-electron…
Preliminary investigations have shown that a family of chalcogenides may be deposited in technologically useful thin film form by an inexpensive technique of spin deposition from solution. The materials which are amorphous and microstructure free retain many of the properties of the solute (e.g., As2S3, As2S2, As2Se3,…
Transmission electron microscopy (at 100 and 1000 kV potential) and analytical scanning transmission electron microscopy were used to study α‐Al 2 0 3 second‐phase particles and their interactions with grain boundaries in two high‐conductivity Y 2 0 3 /Yb 2 0 3 stabilized zirconia ceramics containing deliberate additi…
The intensity of the small-angle X-ray and neutron scattering from a polydisperse system of randomly oriented independently scattering particles is shown to be proportional to h−α for all values of the scattering vector h when the distribution of particle dimensions is proportional to r−(2d + 1 − α), where h = 4πλ−1 s…
The crystal structure of α-SiO2 (low quartz) has been refined at 296, 78, and 13 K from time-of-flight neutron powder diffraction data. The major effect of temperature from 296 to 78 K is a nearly rigid body rotation of the SiO4 tetrahedra. Below 78 K, tetrahedral rotation is substantially reduced giving rise to a muc…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCounterion and solvent effects on the electrode reactions of manganese porphyrinsS. L. Kelly and K. M. KadishCite this: Inorg. Chem. 1982, 21, 10, 3631–3639Publication Date (Print):October 1, 1982Publication History Published online1 May 2002Published inissue 1 October 1982h…
Abstract Quantitative transmission electron microscopy and optical microscopy is used to study craze initiation and growth in thin films of high‐impact polystyrene (HIPS). Dilution of the HIPS with unmodified polystyrene reduces the craze–craze interactions, permitting equilibrium growth and craze micromechanics to be…
Abstract This article is the first of a series devoted to various aspects of exchange reactions in molten bisphenol‐A polycarbonate–poly(butylene terephthalate) mixtures. The statistical aspects of exchange reactions between two polycondensates of different chemical structure are considered. This theoretical approach…
A method of describing the thermal fluctuations in the local atomic structure of liquid and amorphous metals in terms of the fluctuations in the atomic level stresses is proposed. The energy of the system is expressed in terms of these stresses in the elastic approximation. The temperature dependence of the second mom…
Structural properties of the solid alkali cyanides were studied with a recently reported ab initio theory based on the Gordon–Kim electron gas model. The low temperature crystal structures of LiCN, NaCN, KCN, RbCN, and CsCN were examined. The average error in lattice parameters is 2.6% and in lattice dissociation ener…
Neat polymerization of bisphenol-linked phthalonitrile monomers, which contain no active hydrogen atoms, is extremely difficult and requires several days of continuous heating at 260–290°C before a viscosity increase becomes evident. In the presence of a nucleophilic compound such as an organic amine, the cure time an…
We present revised absolute values of the elastic constants and order parameters of several cyanobiphenyls. The calculations make use of our earlier measurements of Freedericksz threshold fields and refractive indices, and corrected values of normalizing constants, particularly in respect of the anisotropy of magnetic…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of viscosity and temperature on torsional relaxation of molecular rotorsRafik O. Loutfy and Bradley A. ArnoldCite this: J. Phys. Chem. 1982, 86, 21, 4205–4211Publication Date (Print):October 1, 1982Publication History Published online1 May 2002Published inissue 1 Octo…
We analyze the structural relationship between microscopic and macroscopic tensors which characterize the linear- and nonlinear-optical properties of molecular crystals exhibiting a strong donor-acceptor intramolecular interaction, with particular reference to methyl-(2,4-dinitrophenyl)-aminopropanoate (MAP). The quas…
Linear elasticity theory is used to describe the stresses around indentations in hard, brittle materials. Unorthodox plasticity theory is introduced, and related to two simple elastic fields. These, combined in varying proportions, are shown to be consistent with many of the crack patterns observed in glasses and cera…
A simple indentation technique for measuring the hardness‐to‐modulus ratio of elastic/plastic materials was developed. The method, which is based on measurement of the elastic recovery of the in‐surface dimensions of a Knoop indentation, allows ready evaluation of the hardness‐to‐modulus ratio to an accuracy better th…
Efficiency of three-wave interactions in molecular crystals depends on the conjugation of the molecular unit, which in turn is a one- or two-dimensional property. This strong anisotropy reduces the number of non-negligible molecular lowest-order hyperpolarizability coefficients to four. The lowest-order macroscopic op…
Diffraction by a dielectric surface-relief grating is analyzed using rigorous coupled-wave theory. The analysis applies to arbitrary grating profiles, groove depths, angles of incidence, and wavelengths. Example results for a wide range of groove depths are presented for sinusoidal, square-wave, triangular, and sawtoo…
Recent developments in the theoretical analysis and experimental study of frequency-dependent loss by relaxation in amorphous semiconductors are reviewed. A unified theoretical treatment of the complex a.c. conductivity is given, within the pair approximation, for single electron tunnelling and hopping in both uncorre…
The linear chain model of Wieting is used here to predict the frequency of the E 1g Raman active mode in the layer compound 2H-niobium selenide. A careful Raman study near this predicted frequency has shown a weak band whose polarisation suggests that it is the E 1g mode.