Materials Literature
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Using a low-temperature molecular-beam epitaxy growth procedure, ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ --- a III-V diluted magnetic semiconductor --- is obtained with Mn concentrations up to $x\ensuremath{\sim}9%.$ At a critical temperature ${T}_{c}$ (${T}_{c}\ensuremath{\approx}50\mathrm{K}$…
A multiple scattering formulation for the electromigration wind force on atoms in dilute alloys is developed. The theory describes electromigration via a vacancy mechanism. The method is used to calculate the wind valence for electromigration in various host metals having a close-packed lattice structure, namely alumi…
Structural optimization is performed for LaMnO${}_{3}$ with the first-principles pseudopotential method based on the local density approximation (LDA), the generalized gradient approximation, and the LDA+U approximation. The Jahn-Teller distortion is reproduced even by LDA but the magnitude of the distortion for all t…
The phase diagram of doped manganate compounds La_{1-x}A_xMnO_3 (with divalent A) is studied. We analyze an extension of the double exchange model using the Schwinger boson formalism. Earlier work by de Gennes on the existence of a canted phase is reproduced, although this phase is shown to be unstable towards phase s…
The controllability of conductivity and the ease of manufacturing/coating of conducting polymers enable tailor- made dielectric loss components for radar absorbing materials (RAM). Different polypyrrole (PPy) based RAM, e.g. paint/rubber containing PPy powder and PPy coated structural phenolic foams with a gradient of…
The flow behavior and the effect of the spinning conditions on the fiber properties and structure of the copolyesters, i.e., samples of copoly(p-hydroxybenzoate-bisphenol A terephthalate), were investigated. The experimental results indicated that the apparent viscosity was affected significantly by shear rate, melt t…
Highly fluorescent Eu-polymer complexes were synthesized through copolymerization of EuPhen(Nap)2AA with methyl methacrylate or styrene and their luminescent properties were investigated. The Eu-polymer luminophores showed intense red emission under UV excitation, and the emission intensities were much stronger than t…
Die Art des Köders bestimmt die Beute : In einem Teich mit Triethanolamin‐Liganden und Eisen(III)‐Ionen gelingt es, sechs‐ und achtgliedrige Eisencoronate 1 bzw. 2 zu fangen, je nachdem, ob man Natrium‐ oder Caesiumionen als Köder verwendet. Dies ist besonders im Zusammenhang mit der Möglichkeit kombinatorischer Ansät…
In this work, the surface treatment of poly(ethylene terephtalate) (PET) films in a low frequency (70 kHz) discharge in helium-oxygen mixtures is investigated. Optical emission spectroscopy and mass spectrometry are used to analyze the gas phase. Surface properties are analyzed via the X-ray photoelectron spectroscopy…
Angular distributions of valence photoelectrons showing effects due to higher-multipole photon interactions have been measured for the first time. Neon 2s and 2p photoemission exhibits effects beyond the dipole approximation throughout the 250 - 1200 eV photon-energy range studied. The results suggest that any photoem…
Methacrylic acid (MA) was graft polymerized onto starch using Ce4+ initiator in aqueous medium. The dependence of grafting on the reaction variables, such as monomer and initiator concentration and time and temperature, was studied in detail. Acid hydrolysis and infrared (IR) spectroscopy were used for the confirmatio…
Polyurethane elastomers based on polyols such as polycaprolactone diol of molar mass 2000 and polytetramethylene glycol of molar mass 2000; diisocyanantes such as diphenyl methane 4,4′ diisocyanate and dicyclohexyl methane 4,4′ diisocyanate; and chain extenders such as bisphenol-A, bisphenol-S,bisphenol-AF, and their…
We perform a comprehensive study of the formation of three dimensional (pyramidal) structures in a large range of conditions, including the possible evaporation of adatoms from the surface and the presence of surface defects. We compare our computer simulations to theoretical calculations of the growth and find good a…
Thin films are usually obtained by depositing atoms with a continuous flux. We show that using a chopped flux changes the growth and the morphology of the film. A simple scaling analysis predicts how the island densities change as a function of the frequency of the chopped flux in simple cases where aggregation is irr…
A helical staircase structure is observed for the layers made from chains of alternating AgI centers and pytz ligands in [Ag(pytz)(NO3)]∞ (pytz = 3,6-di-(4-pyridyl)-1,2,4,5-tetrazine). Decisive for the formation of this array—a view of the structure along the helical axis is shown on the right—is the anionic ligand NO…
The electronic structure of interfaces between lattice-mismatched semiconductor is sensitive to the strain. We compare two approaches for calculating such inhomogeneous strain -- continuum elasticity (CE, treated as a finite difference problem) and atomistic elasticity (AE). While for small strain the two methods must…
We investigate the performance of the GW approximation by comparison to exact results for small model systems. The role of the chemical potentials in Dyson's equation as well as the consequences of numerical resonance broadening are examined, and we show how a proper treatment can improve computational implementations…
Because of the subgroup - group relationship which exists between the space group of yellow InCl and that of rock salt , a Landau expansion of the free energy in invariants of the symmetry group of higher order can be performed and a mechanism for distortion arises. The special feature of this hypothetical phase trans…
The one- and two-electron ground-state energies of singly and doubly charged silicon (Si) dots modelled by a sphere covered with a silicon dioxide layer embedded in various dielectric media can be calculated as functions of the sphere size and the thickness of the oxide by extending the work of Allan et al and Babic e…
Room-temperature visible luminescence from Pr3+ ions embedded in germaniumsulfide glass hosts is reported along with edge luminescence from these hosts. The important role of energy transfer processes between the host and Pr ions is demonstrated experimentally through the dependencies of photoluminescence on excitatio…