Materials Literature
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Abstract Optical properties and stability of hydrogenated silicon clusters are investigated using density functional pseudopotential calculation. The dipole transitions between the band‐edge orbitals are allowed, in contrast to the indirect gap in bulk silicon. Evolution of a small amount of hydrogen atoms enhances th…
Abstract Experimental results on 3 d O h complexes in insulators reveal that 10 Dq α R − n , where R is the metal–ligand distance and n is close to five. This strong dependence determines the Huang–Rhys factor, S ( A 1 g ), associated to the symmetric A 1 g mode of the first excited state of complexes like MnX and CrX…
Abstract The geometrical structures and properties of small cationic boron clusters B ( n = 2–14) have been investigated using the local spin density ( LSD ) formalism. The nonlocal correction has also been calculated. The linear search for minima on the potential energy surface has been performed using analytical gra…
Exciton effects on soliton and bipolaron lattice states are investigated using an electron-lattice Peierls model with long-range Coulomb interactions. The Hartree-Fock (HF) approximation and the single-excitation configuration- interaction (single-CI) method are used to obtain optical absorption spectra. We discuss th…
Optical thin film multilayer systems at oblique angles of incidence exhibit polarization effects because of the differences between the reflectances, transmittances, and phase shifts of the p and s states of polarization. It is shown that a thin film system is equivalent to a combination of two polarization elements,…
Variable angle of incidence spectroscopic ellipsometry (VASE) is commonly used for multilayer optical analysis, but in some cases this experiment (performed in reflection) does not provide sufficient information for the unique determination of the thicknesses and optical constants of the films in the given multilayer.…
Packing transitions in the lowest energy structures of Li clusters as a function of size have been identified via simulated annealing. For N>21, the large $p$ character of Li leads to unexpected ionic structures. At N~25, a packing pattern based on interpenetrating 13-atom icosahedra and similar to that of Na and K ap…
Magnetization and ESR spectroscopic data indicate a high-spin ground state (S = 4) for 1 in frozen solution. A related acyclic pentaradical also has a high-spin ground state (S = 5/2). These compounds may be the first step towards understanding the impact of defects on spin coupling in multi-site molecules.
Abstract For corrigendum see DOI: 10.1002/anie.199502401
An average NiNNi angle of only 84° is found in the end-on bridges in complex 1. This small angle possibly explains the antiferromagnetic coupling of the nickel centers in 1. For more than 20 years it has been assumed that end-on coordination should lead to ferromagnetic coupling. The complex occurs as one-dimensiona…
Many forms of chemical bonding are exhibited by Al in intermetallic and Zintl phases. This is revealed by the calculation of the electron localization function for the series Al, CaAl 2 , SrAl 2 , BA1 4 , CaAl 2 Si 2 , and Si. With this procedure it is possible to distinguish clearly between metallic, covalent multice…
Abstract Transition metal chemistry contains a class of complex compounds for which the spin state of the central atom changes from high spin to low spin when the temperature is lowered. This is accompanied by changes of the magnetic and optical properties that make the thermally induced spin transition (also called s…
Ce-containing chalcogenides may exhibit interesting chromatic properties due to the presence of a CeIII-5f/CeIII-4d gap. In such insulating materials, color varies from red to yellow depending on the covalent character of the Ce–S bond. Thanks to this correlation, a continuous modification of the Ce–S bond characteris…
The localized excitations in the competing bond-order-wave(BOW), charge-density-wave(CDW), and spin-density-wave(SDW) systems are investigated within the Bogoliubov-de Gennes formalism using an extended Peierls-Hubbard model. An extensive study of localized excitations over a wide range of the on-site e-ph coupling λ2…
A series of reactor design studies based on the Tokamak configuration have been carried out under the direction of Professor Robert Conn of UCLA. They are called ARIES-I through IV. The key mission of these studies is to evaluate the attractiveness of fusion assuming different degrees of advancement in either physics…
Fatigue‐crack growth behavior under cyclic tension‐tension loading has been examined in a 30‐vol%‐TiB 2 ‐reinforced β‐SiC matrix composite, using compact tension specimens tested at temperatures from 750° to 850°C in a furnace air environment. Cyclic fatigue‐crack growth rate was found to depend strongly on testing te…
Abstract Crosslinked 1,4-poly butadiene (BR) and styrene-butadiene rubber (SBR) were oxidized in various ionic environments (water, neutral salt solutions, acidic and basic buffers). The acceleration of oxidation when the elastomer was immersed in neutral and basic aqueous solutions, compared to dry air, is consistent…
Potentiometric evalution of the interaction between aluminium(III) and the hydroxy carboxylates 3-deoxy-D-ribo-hexonate (L1H) and 2,5-dihydroxypentanoate (L2H) provided evidence for the formation of 1:1 complexes only, though with the ligand being present in singly, doubly and quadruply deprotonated forms in the hexon…
Abstract The autoignition temperature and composition of 15 carbon‐filled fluoroelastomers have been determined. These experimental data and three sets of literature data are used to examine the relationship between autoignition temperature and rubber composition. The autoignition temperature at an elevated oxygen pre…
The formation and evolution of the gap states formed with increasing Cs concentration in thin 6P films are followed with ultraviolet photoemission spectroscopy (UPS) and indirectly with energy loss spectroscopy involving electronic transitions (EELS). Two distinct doping regimes are apparent, in the lower doping regim…