Materials Literature
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A perturbation theory of the static response of insulating crystals to homogeneous electric fields, that combines the modern theory of polarization (MTP) with the variation-perturbation framework is developed, at unrestricted order of perturbation. First, we address conceptual issues related to the definition of such…
It is shown that the double-exchange Hamiltonian, with weak antiferromagnetic interactions, has a rich variety of first-order transitions between phases with different electronic densities and/or magnetizations. The paramagnetic-ferromagnetic transition moves towards lower temperatures, and becomes discontinuous as th…
We present experimental data, numerical simulations, and analytical transfer-matrix calculations for a two-dimensionally isotropic, left-handed metamaterial (LHM) at X-band microwave frequencies. A LHM is one that has a frequency band with simultaneously negative εeff(ω) and μeff(ω), thereby having real values of inde…
ZnO nanowires were mass produced using a physical vapor deposition approach. The ZnO nanowire monocrystallites have an average diameter around 60 nm and length up to a few micrometers. The unidirectional growth of the ZnO nanowires was controlled by the conventional vapor-liquid-solid mechanism. Intensive UV light emi…
Influence of electron-electron relaxation processes on Auger recombination rate in direct band semiconductors is investigated. Comparison between carrier-carrier and carrier-phonon relaxation processes is provided. It is shown that relaxation processes are essential if the free path length of carriers doesn't exceed a…
The paper presents a comparative discussion of stress update algorithms for single-crystal plasticity at small strains. The key result is a new unified fully implicit multisurface-type return algorithm for both the rate-independent and the rate-dependent setting, endowed with three alternative approaches to the regula…
Quantum confinement effects on the optical properties of ion beam sputtered nickel oxide thin films are reported. Thin films with crystallite sizes in the range 9 to 14 nm have been deposited on to fused silica substrates. There is an increase in band gap, from 3.4 to 3.9 eV, and a decrease in refractive index, from 2…
In this paper we present a theoretical study of the linkage isomerization in [Co(NH 3 ) 5 ONO] 2+ . In particular, we have used for our analysis a hybrid density functional/Hartree−Fock method for the electronic computations (the so-called B3LYP), while a recent version of the polarizable continuum model has been cons…
Department of Fine Chemistry, Seoul National University of Technology, Seoul 139-743, KoreaReceived April 18, 2000Keywords: Porphyrin, Epoxidation, Hydroxylation, Oxoiron.Since the selective oxidations of hydrocarbons are ofimportance in both synthetic chemistry and industrial pro-cesses, biomimetic oxidation reaction…
Calcium phosphate precipitation obtained from aqueous solutions at room and body temperature and pH 5.5-7.5 were investigated by high-resolution transmission electron microscopy (HRTEM), transmission electron diffraction, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Supersaturated solutions of calci…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTMacroscopic Shear Alignment of Bulk Transparent Mesostructured SilicaN. A. Melosh, P. Davidson, P. Feng, D. J. Pine, and B. F. ChmelkaView Author Information Departments of Chemical Engineering and Materials University of California, Santa Barbara, California 93106 Lab…
We characterize shear-induced states of order and disorder in a symmetric lamellae forming poly(cyclohexylethylene) (C)−polyethylene (E) CECEC pentablock copolymer. When subjected to a large amplitude reciprocating shear strain (γ = ±600%) in the ordered lamellae state, the sample rapidly aligns in a perpendicular ori…
We present data from Monte Carlo simulations for monodisperse linear polymer chains in dense melts with degrees of polymerization between N = 16 and N = 512. The aim of this study is to investigate the crossover from Rouse-like dynamics for short chains to reptation-like dynamics for long chains. To address this probl…
Nanosized ZnS has been prepared inside MCM-41 hosts by two related schemes, both of which are derived from surface modification methods. The ZnS-containing MCM-41 samples with and without the functional groups (ethylenediamine groups in this case) were designated as ZnS−ED−MCM-41 and ZnS−MCM-41(cal), respectively. The…
The Boltzmann Transport Equation (BTE) for phonons best describes the heat flow in solid nonmetallic thin films. The BTE, in its most general form, however, is difficult to solve analytically or even numerically using deterministic approaches. Past research has enabled its solution by neglecting important effects such…
Es ist ironisch, dass die Röntgen-Photoelektronenspektroskopie zum empfindlichen Nachweis für starke Wasserstoffbrückenbindungen (low-barrier hydrogen bonds) in Tetrapyrrolen dienen kann, obwohl mit ihr normalerweise alle Elemente außer Wasserstoff nachweisbar sind. Die Stickstoff-1s-Peaks (siehe Diagramm) fallen nie…
Largely monodisperse, crystalline nanoscale oxide particles (for example, Cu2O, TiO2, Nb2O5) are preparatively accessible with the polyol method (see picture). The colloidal suspensions of the particles thus obtained can be employed readily for the homogeneous coating of various substrates (for example, glass plates,…
The structural effects induced by ion exchange of NH 4 + by Co 2+ cations in the series of ferrierites were investigated by electron spectroscopy for chemical analysis (ESCA). The utility of the Auger parameter α‘of framework Al for the estimation of the extent of ion exchange of NH 4 + by Co 2+ cations is demonstrate…
24-gliedrige Ringe bauen die zweidimensionale Struktur der neuartigen Verbindungen [NdM(bpym)(H2O)4(CN)6]⋅3 H2O (M=Fe (1), Co (2); bpym=2,2′-Bipyrimidin) auf. Dies sind die ersten zweidimensionalen cyanoverbrückten Verbindungen mit Lanthanoid- und Übergangsmetallzentren (siehe Bild). Außer ihren Strukturen wurden auch…
It is ironic that although it is typically a technique that "sees" all elements other than hydrogen atoms, X-ray photoelectron spectroscopy (XPS) acts as a sensitive probe of low-barrier hydrogen bonds, as seen in a study of free-base tetrapyrroles. The nitrogen 1s XPS peaks never quite coalesce, even when the N⋅⋅⋅H⋅⋅…