Materials Literature
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The fluctuation-dissipation theorem (FDT), connecting dielectric susceptibility and polarization noise, was studied in glycerol below its glass transition temperature ${T}_{g}$. Weak FDT violations were observed after a quench from just above to just below ${T}_{g}$, for frequencies above the $\ensuremath{\alpha}$ pea…
The physical properties of the new high-pressure spinel phase of ${\mathrm{Si}}_{3}{\mathrm{N}}_{4}$ and ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ were studied by first-principles calculations. The presence of Si at the octahedral site and the elongated Si-N bonds under pressure have a profound effect on many properties of $…
Epitaxial zinc oxide films have been prepared on gallium nitride (0002) substrates by cathodic electrodeposition in an aqueous solution containing a zinc salt and dissolved oxygen at 85 °C. The films have the hexagonal structure with the c axis parallel to that of GaN and the [100] direction in ZnO parallel to the [10…
An explanation is given for the charge order, orbital order, and insulating state observed in half-doped manganese oxides, such as ${\mathrm{Nd}}_{1/2}{\mathrm{Sr}}_{1/2}{\mathrm{MnO}}_{3}$. The competition between the kinetic energy of the electrons and the magnetic exchange energy drives the formation of effectively…
Direct beam x-ray imaging, with intense coherent monochromatic synchrotron radiation and a fast readout low noise detector has been used for in situ studies of cellular and dendritic solidification of Sn-Pb alloys. Temporal and spatial resolutions down to $\ensuremath{\sim}0.7\mathrm{s}$ and $\ensuremath{\sim}2.5\ensu…
We calculate the properties of $p\ensuremath{-}n$ junctions, $n\ensuremath{-}i$ junctions, and Schottky barriers made on a single-wall carbon nanotube. In contrast to planar bulk junctions, the depletion width for nanotubes varies exponentially with inverse doping. In addition, there is a very long-range (logarithmic)…
We address the effects of disorder on the conducting properties of metal and semiconducting carbon nanotubes. Experimentally, the mean free path is found to be much larger in metallic tubes than in doped semiconducting tubes. We show that this result can be understood theoretically if the disorder potential is long ra…
We report the first ab initio density-functional study of <111> screw dislocations cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Co…
Spectroscopic and magnetic studies on α-Li 3 Fe 2 (PO 4 ) 3 show an interesting behavior below the transition temperature (29 K). The compound orders antiferromagnetically, presenting a weak ferromagnetic moment, which diminishes with temperature. In the same region of temperatures, the Mössbauer spectra split in two…
Siloxane-anchored monolayer films are best prepared by the self-assembly of trichlorosilanes. The moisture sensitivity and chemical reactivity of the trichlorosilane moiety complicates the synthesis and purification of the ω-functionalized alkyltrichlorosilanes that are the building blocks for functionalized monolayer…
For developing clinically useful porphyrin drugs, it is essential to characterize porphyrin−membrane interactions and to determine the factors that modulate such interactions. To this end, four uniquely p -phenyl-substituted tetraphenylporphyrins were synthesized. These water-insoluble, unsymmetrically substituted por…
A series of block polymers were synthesized from tetrahydropyranyl methacrylate (THPMA) and several fluorinated methacrylates. By changing both the length of the fluorinated side chain and the nature of its end group, the surface properties of these polymers were greatly influenced. The polymers with perfluoroheptyl g…
The bonding of triethylphosphine oxide (TEPO) to the acid site of a surface produces a systematic change in the phosphorus-31 isotropic chemical shift that is proportional to the acid strength of the adsorption site. The acidity of several amorphous solid acids of various strengths, several zeolites (HZSM-5, HY, TS-1,…
Ca 2 FeMoO 6 perovskite has been prepared in polycrystalline form by controlled reduction of previously decomposed citrate precursors. This material has been studied by X-ray and neutron powder diffraction (NPD), scanning electron microscopy, thermal analysis, and magnetic and magnetotransport measurements. The crysta…
The fabrication of boron nitride nanotubules and BN-based composite nanostructures within the pores of anodic aluminum oxide is described. Boron nitride nanotubules are produced by pyrolyzing 2,4,6-trichloroborazine over alumina templates at 750 °C. The nanotubules are polycrystalline, with crystallites exhibiting an…
Argon adsorption isotherms were measured at 87 K for two macroporous silicas and a series of high-quality MCM-41 silicas with approximately cylindrical pores of average diameters from 2 to 6.5 nm. The pore sizes of the MCM-41 samples were accurately determined in earlier studies on the basis of powder X-ray diffractio…
We present an unambiguous formulation for the total energy density within density-functional theory. We propose that it be used as a tool for the interpretation of computed energy and electronic structure changes during structural transformations and chemical reactions, augmenting the present use of electron density c…
The solubility of rare earths at a level of 0.5 mol% in traditional heavy metal oxide glasses based on bismuth, lead and gallium is limited to the largest cations Pr, Nd and Sm. Within the families of these oxide glasses, a higher level of doping was achieved in this work with a heavy metal oxide glass containing germ…
We describe a color separation optical element with potential display applications that is designed to separate light into an array of red, green, and blue stripes formed at a certain distance from the component. The stripe color separation grating is a surface-relief diffractive optical element composed of a repeated…
A series of 9-phenylcarbazole ethynylene monodenrons have been prepared by palladium-catalyzed coupling reactions creating well-organized arrays of redox centers. The tert-butyl groups attached to the 3,6-positions of peripheral 9-phenylcarbazole monomers provide adequate solubility to a limited degree. Trimer and 7-m…