Materials Literature
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The single particle dynamics of a 2D liquid made up of soft disks interacting by a repulsive r−12 potential are studied using molecular dynamics simulations. We find that mean squared particle displacement 〈Δr(t)2〉 behaves diffusively, i.e., increases linearly with time, within a time interval tc very much shorter tha…
X-ray-diffraction observations of strains induced by vapor adsorption are reported for porous silicon single-crystal samples. Two types of porous silicon ($p$ and ${p}^{+}$) with very different pore structure are investigated. A low-pressure contraction is observed in $p$-type samples with spherical pores of about 3-n…
By use of femtosecond differential absorption spectroscopy the electron-hole pair relaxation times have been determined in CdSe quantum dots with excited state energies larger than the LO-phonon energy. The fast energy relaxation within 500 fs is independent of the relation between level spacing and LO-phonon energy a…
In this work we present a study of the magnetic and transport properties of the system ${\mathrm{LaNiO}}_{3\mathrm{\ensuremath{-}}\mathit{x}}$ (0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.5) where the x=0 member is a well-known metallic oxide. We found that the x=0.5 compound is an antiferromagnetic insulator at r…
In order to study the electrical transport of holes in LaCo${\mathrm{O}}_{3}$, the bulk conductivities and dielectric properties in a polycrystalline specimen were investigated. The bulk conduction was separated from others by complex-plane impedance analysis. At high temperatures, i.e., $T>170$ K, the activation e…
We present a theory for the calculation of the self-consistent-field dynamical polarizability and hyperpolarizabilities of molecular solutes described within the framework of the polarization continuum model. The formulation is characterized by the use of a cavity accurately modeled on the molecular shape of the solva…
An efficient continuum model for simulating polymer blends and copolymers is presented. In this model, the interactions are short-range and purely repulsive, thus allowing for excellent computational performances. The driving force for phase separation is a difference in the repulsive interaction strength between like…
Recombination processes in rare-earth metals in semiconductors are a special case due to the localized nature of $f$ electrons. Our work explores in detail the radiative and nonradiative mechanisms of energy transfer for erbium in silicon by investigating the temperature dependence of the intensity and the decay time…
We study the processes of charge separation and transport in composite materials formed by mixing cadmium selenide or cadmium sulfide nanocrystals with the conjugated polymer poly(2-methoxy,5-(2\ensuremath{'}-ethyl)-hexyloxy-$p$-phenylenevinylene) (MEH-PPV). When the surface of the nanocrystals is treated so as to rem…
Finite graphite systems having a zigzag edge exhibit a special edge state. The corresponding energy bands are almost flat at the Fermi level and thereby give a sharp peak in the density of states. The charge density in the edge state is strongly localized on the zigzag edge sites. No such localized state appears in gr…
Acid-treated carbon nanotubes have been decorated with nanoscale Au, Pt and Ag clusters by employing several procedures. The nature and extent of metal coverage can be varied by changing the concentration of the metal compound or by mild sonication (treatment with ultrasound). The metal clusters seem to get deposited…
The transition metal chalcogenide Ni(S,Se)2 is one of the few highly correlated, Mott-Hubbard systems without a strong first-order structural distortion that normally cuts off the critical behavior at the metal-insulator transition. The zero-temperature (T) transition was tuned with pressure, and significant deviation…
Open carbon nanotubes were filled with molten silver nitrate by capillary forces. Only those tubes with inner diameters of 4 nanometers or more were filled, suggesting a capillarity size dependence as a result of the lowering of the nanotube-salt interface energy with increasing curvature of the nanotube walls. Nanotu…
In spite of considerable effort, the understanding of the molecular structure of polyacry-lonitrile-based fibers is still incomplete. This paper shows that molecular modeling based on molecular mechanics and dynamics can be used to study the molecular structure of polyacrylonitrile-based fibers with appropriate strate…
Multiblock copolymers offer the possibility to combine the properties of different polymers. Thus, new materials with tailor-made unique properties are available by coupling of different suitable polymeric segments. The goal of the work discussed in this paper was to combine advantageous properties of liquid-crystalli…
Freshwater ecosystems are a major component of the northern environment. The application of new limnological technologies and approaches to these ecosystems is producing a revised perspective on their structure and dynamics, and is leading to insights into their potential response to global change processes. The plank…
The first comprehensive survey on the uses of alkyl polyglycosides as renewable ressources for the chemical industry. Experts from industry show in detail how alkyl polyglycosides can help chemists to improve their products. Since quite a few years, renewable Ressources are of increasing interest for the chemical indu…
The improvement of flame-retardation of thermosetted epoxy–amine resins was attempted by chemically incorporating phosphorus-containing reagents. By reacting 4,4′-diglycidylether of bisphenol A (DGEBA) with dialkyl (or aryl) phosphate, it was possible to chemically modify the epoxy resin and then cure it in the presen…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectral Dynamics of Individual Molecules in Glasses and CrystalsE. Geva, P. D. Reilly, and J. L. SkinnerView Author Information Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706Cite this: Acc. Chem. Res. 1996, 29,…
We reconsider a number of measurements for the overall hydration kinetics of tricalcium silicate pastes having an initial water to cement weight ratio close to 0.5. We find that the time dependent ratio of hydrated and unhydrated silica mole numbers can be well characterized by two power-laws in time, $x/(1-x)\sim (t/…