Materials Literature
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The size dependent electronic absorption spectra of CdSe nanocrystals have been measured in a diamond anvil cell. Under pressure, these nanocrystals are reversibly converted from a direct gap wurtzite structure to a rock salt structure which has an indirect gap in the bulk. It is thus possible to compare the influence…
Abstract Microbeads possessing amine functionality at the surface have been prepared by two methods: In the first method, poly(4‐vinylpridine/styrene) P(4VP/S) copolymer microbeads containing 13–69 mol % 4‐vinylpridine (4VP) were synthesized from the monomers. In the second method, animated polystyrene (PS) particles…
Abstract The reaction of poly(ethylene terephthalate) (PET) melts with ethylene glycol was examined in a pressure reactor at temperatures above 245°C. The reaction rate was found to depend on temperature and on the concentrations of liquid ethylene glycol and of ethylene diester groups in the polymer. A kinetic model…
Using density-functional theory we investigate several properties of Al(111), Al(100), Al(110), and stepped Al(111) surfaces. We report results of formation energies of surfaces, steps, adatoms, and vacancies. For the adsorption and diffusion of Al on flat regions of Al(111) surfaces we find the hcp site energetically…
Abstract The mechanical properties of composites of granular starch and low density polyethylene (PE) have been studied as functions of starch volume fraction ϕ, granule size, and presence of compatibilizer. Property–volume fraction relationships were interpreted using various theories of composite properties. The dep…
Heterogeneous materials, such as rock, have extreme nonlinear elastic behavior (the coefficient characterizing cubic anharmonicity is orders of magnitude greater than that of homogeneous materials) and striking hysteretic behavior (the stress‐strain equation of state has discrete memory). A model of these materials, t…
An energy functional for orbital based $O(N)$ calculations is proposed, which depends on a number of non orthogonal, localized orbitals larger than the number of occupied states in the system, and on a parameter, the electronic chemical potential, determining the number of electrons. We show that the minimization of t…
Composite sheets and nanotubes of different morphologies containing carbon, boron, and nitrogen were grown in the electric arc discharge between graphite cathodes and amorphous boron-filled graphite anodes in a nitrogen atmosphere. Concentration profiles derived from electron energy-loss line spectra show that boron a…
Introduction The discovery that certain classes of polymers may acquire high electronic conductivity following chemical or electrochemical treatment has opened a new and exciting area of research and development. The concept of electric transport in polymers due to the availability of polymeric materials with characte…
An electro-optic coefficient of r = 0.05 ± 0.02 pm/V is reported for a temperature/electric field poled Ge:SiO2 fibre. The fibre was a commercial, polarisation maintaining, singlemode (633 nm) fibre with a core composition of 18 wt% Ge and a fused silica cladding. Piezoelectric effects are seen at low frequency. Compa…
While the small sticking coefficient for molecular hydrogen on the Si(001) surface apparently requires a large energy barrier of adsorption, no such barrier is observed in desorption experiments. We have calculated the potential-energy surface of an H_2 molecule in front of a Si(001) surface. If we relax the Si substr…
A new method of solution to the local spin density approximation to the electronic Schrödinger equation is presented. The method is based on an efficient, parallel, adaptive multigrid eigenvalue solver. It is shown that adaptivity is both necessary and sufficient to accurately solve the eigenvalue problem near the sin…
An existing family of genetic algorithms, which were designed with discrete and binary variables in mind, has been extended in this paper to handle truly continuous variables. Its close relationships with Monte Carlo methods, the simplex method, simulated annealing and other direct, i.e. Derivative-free global optimiz…
The structural phase sequence of (C 3 H 7 NH 3 ) 2 CuCl 4 (abbreviated to C 3 CuCl) has been determined between 20 and 300 K by optical and x-ray methods. The Jahn-Teller compound undergoes two types of reconstructive phase transition between antiferrodistortive (AF) and ferrodistortive (F) structures: the first may b…
The synthesis and physical characterization of Nd 1-x La x NiO 3- delta (from x=0 to 1) samples are reported. Nd 1-x La x NiO 3- delta samples are orthorhombic for x<or=0.4 and rhombohedral for x>0.4. Resistivity and magnetic susceptibility measurements from 4.2 K to 300 K are also reported. The increase of La content…
Antiferroelectric behavior is not exhibited by the liquid crystalline phases of 1, n = 10, 12, 14, 16. This indicates new prospects for novel polar materials. Antiferroelectric behavior in 1 is prevented by the polymeric structure (·· MoO … MoO··) of the mesophase and its hexagonal symmetry. The range of mesophase s…
Abstract The application of some polymers as nucleating agents for polypropylene has been examined. Among various polymeric nucleating agents, polycyclopentene was found to be a superior nucleating agent to typical organic nucleating agents. When polycyclopentene was added to polypropylene, the crystallization tempera…
A quantitative study of the effect of electric field on the stripe domains formed by layer deformation in chiral smectic A liquid crystals is presented. X-ray diffraction studies reveal that the angle between the layer normals in adjacent stripe domains increases with increasing electric field. A simple model is prese…
Thin films of (La1−xCax)MnO3 prepared by laser ablation deposition are ferromagnetic when 0.2≤x≤0.5 with Tc≊250 K. These films show strong Faraday rotation both in the vicinity of the 2p(O)→3d(Mn) charge-transfer absorption at approximately 3.0 eV (θF≳40 000°/cm), and in the vicinity of the 3d(t2g)→3d(eg) excitation a…
We demonstrate that the Hubbard correlation among Ni $3d$ electrons is able to reproduce the insulating character of NiO, the correct value of the gap, the orbital character of the valence band edge, and the presence of satellite structures. We have determined the quasiparticle spectra starting from the complex single…