Materials Literature
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Complex mathematical models are increasingly being used as predictive tools and as aids for understanding the processes underlying observed chemical phenomena. The parameters appearing in these models, which may include rate constants, activation energies, thermodynamic constants, transport coefficients, initial condi…
It is proposed to apply the direct measurement of spontaneous polarization using triangular waves to ferroelectric liquid crystals. The use of the triangular waves allows us to easily subtract the background contribution due to the conductive and the capacitive current and to accurately determine the spontaneous polar…
The "inherent structures" which underlie the liquid state are those stable particle packings (potential minima) which can be reached by a steepest-descent quench on the potential-energy hypersurface. This paper explores the dynamics of transition between distinct inherent structures for a simple classical model of mon…
Machine learning (ML) is transforming all areas of science. The complex and time-consuming calculations in molecular simulations are particularly suitable for an ML revolution and have already been profoundly affected by the application of existing ML ...Read More
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChain-length dependence of electronic and electrochemical properties of conjugated systems: polyacetylene, polyphenylene, polythiophene, and polypyrroleJ. L. Bredas, R. Silbey, D. S. Boudreaux, and R. R. ChanceCite this: J. Am. Chem. Soc. 1983, 105, 22, 6555–6559Publication…
The dielectric function of an inhomogeneous system consisting of small particles in a dielectric host material is investigated using a lattice gas model to describe the topological disorder among the particles. By applying the coherent potential approximation, an effective single-particle polarisability is found, whic…
The integrated intensities and full width at half maximum (FWHM) of the 80 cm -1 Raman bands (hard modes) of ferroelastic Pb 3 (PO 4 ) 2 and Pb 3 (P 0.77 As 0.23 O 4 ) 2 were investigated in both the ferro and 'intermediate' phases for different polarisations as functions of temperature. The observed behaviour of thes…
This Symposium on "The Effects of Hostile Environments on Plastics" is to honor a Plastics Pioneer, Raymond B. Seymour. The co-chairmen David Garner and G. A. Stahl as well as this speaker are former graduate students of Dr. Seymour.
Organic molecular crystals exhibit three-wave nonlinear mixing efficiencies one or two orders of magnitude above that of Lithium Niobate. Beyond the basic common molecular features of these crystals (conjugation and intra-molecular charge transfer), different possibilities to achieve a proper lattice orientation (chir…
Studies of the basic physics of nonlinear second order optical processes in solids remain critically important to the field of nonlinear optics and to further advances in telecommunications technologies. This fact receives continued emphasis today in problems of current interest such as phase conjugation and optical b…
Over the past decade it has been learned that organic materials containing appropriately constituted or substituted conjugation systems may exhibit highly enhanced electronic nonlinear optical polarization responses ( 1 - 4 ). Since the microscopic second-order nonlinear hyperpolarizability tensor, β, is orientational…
The electron paramagnetic resonance (EPR) and Mössbauer properties of native horseradish peroxidase have been compared with those of a synthetic derivative of the enzyme in which a mesohemin residue replaces the natural iron protoporphyrin IX heme prosthetic group. The oxyferryl pi cation radical intermediate, compoun…
The exchange interaction between ${^{3}\ensuremath{\Sigma}_{\mathrm{g}}}^{\ensuremath{-}}$ ${\mathrm{O}}_{2}$ molecules, as obtained from ab initio calculations for a singlet, triplet, and quintet dimer, can be well represented by the Heisenberg Hamiltonian. The coupling parameter $J$ depends exponentially on the ${\m…
A general class of models is introduced which relate the motion of a phase boundary to properties of the local interfacial geometry. These systems can undergo successive destabilizations as they grow, possibly giving rise to nonequilibrium spatial patterns. This formalism has applications to a wide variety of physical…
For pt.II see ibid., vol.16, p.2455 (1983). The temperature and pressure dependences of the elastic and strain-related properties of the 'pseudo-proper' ferroelectric material BiVO 4 have been determined using mean-field theory. In the tetragonal paraelastic phase the elastic constants c 11 -c 12 , c 66 and c 16 are a…
For pt.IV see ibid., vol.16, p.5119 (1983). Measurements of the Bi 3+ displacement and the primary and secondary spontaneous strains in the ferroelastic material BiVO 4 have been made as a function of temperature by single-crystal X-ray diffraction. The results are discussed using both macroscopic and microscopic mean…
For pt.V see ibid., vol.16, p.5127 (1983). The relationship between the domain wall orientation and the spontaneous strain in ferroelastics is discussed, with particular reference to the W' walls in BiVO 4 . The microscopic, wall-defining property is shown to be the coherence of the lattices of the twin components. Th…
The effect of doping of Tl upon thermoluminescence, its emission and optical absorption in flux grown BaFCl crystals is investigated. Besides an increase in luminescence output, X/γ-irradiations of BaFCl: Tl crystals produce three additional glow peaks at 450,465, and 500 K and a TL emission spectrum at 460 nm. Optica…
The grain cathodoluminescence (CL) properties of bariumtitannte ceramics, sintered at, different oxygen partial pressures are systematically investigated. The spectra are found to be composed of different bands, the intensities of which depends strongly on the specimen temperature and on the oxygen partial pressure of…
In the analysis of the thermoluminescence glow curves, and in particular when applied to TL dosimetry and TL dating of archaeological and geological samples, a first order behaviour of the peaks involved is usually implicitly assumed. In this work the TL response for second order kinetics is described and shown that t…