Materials Literature
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In recent experiments on sodium chloride clusters, structural transitions between nanocrystals with different cuboidal shapes were detected. Here we determine reaction pathways between the low-energy isomers of one of these clusters, ${(\mathrm{NaCl})}_{35}{\mathrm{Cl}}^{\mathrm{\ensuremath{-}}}.$ The key process in t…
Silicon clusters and nanocrystals containing up to several thousand atoms per cluster have been generated by pulsed ${\mathrm{CO}}_{2}$-laser-induced decomposition of ${\mathrm{SiH}}_{4}$ in a flow reactor. By introducing a conical nozzle into the reaction zone, the nascent clusters are extracted into a molecular beam…
When multiple elastic diffraction peaks are obtained from an x-ray or neutron source, data analysis is commonly performed using a Rietveld refinement applied to the entire pattern, rather than simply performing single peak fits. In the simplest case the crystal structure is assumed to be ideal despite the presence of…
Quantitative roughness and microstructural analysis of as-deposited Al films, 0.1–1.0 μm thick, were performed by atomic force microscopy (AFM), one-dimensional power spectral density analysis (1DPSD), transmission electron microscopy, and x-ray pole figure methods. The variation of grain size (d) with thickness (h) i…
Ferromagnetic coupling between metal centers and end-to-end coordination of the azido bridges were found together for the first time in the one-dimensional nickel(II) compound [{Ni(5-methylpyrazole)4(N3)}n](ClO4)n⋅n H2O (1; the structure in the unit cell is shown). The ferromagnetic coupling involving spin canting occ…
E-field induced phase transformation and associated changes in dielectric/piezoelectric properties of 〈001〉-oriented rhombohedral 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 crystals were investigated. The longitudinal strain level was found to abruptly increase at 20 kV/cm, corresponding to that where an induced phase appears wi…
Polyhydroxyalkanoic acids (PHA) are carbon and energy storage polymers that accumulate in inclusion bodies in many bacteria and archaea in response to environmental conditions. This work presents the results of a study of PHA inclusion body-associated proteins and an analysis of their coding region in Bacillus megater…
Twin wall related diffuse scattering intensities from a single crystal of LaAlO3 were determined using high-resolution x-ray diffraction methods. Rocking curves were measured for sample temperatures between 295 and 900 K. The wall thickness W was determined by comparing the observed diffraction profiles with structure…
High resolution valence- and core-level photoemission spectra of undoped and 3% Sb-doped ${\mathrm{SnO}}_{2}$ are presented. Conduction-band occupation due to Sb doping in ${\mathrm{SnO}}_{2}$ leads to a shift of valence-band features to high binding energy. However, the shift is less than the width of the occupied pa…
An analytical expression for the energy loss suffered by a fast electron passing near a homogeneous dielectric sphere is derived within a fully relativistic approach. The sphere is described by a frequency-dependent dielectric function. The electromagnetic field induced by the passage of the electron is then obtained…
Making use of a combination of metal–ligand coordination interactions and solvophobic forces, an oligomer based on phenylacetylene incorporates Ag+ ions to form a highly ordered helical structure. The space-filling model shown makes clear the trigonal-planar coordination environment at silver.
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTControlled Growth of Gold Nanoparticles during Ligand ExchangeLeif O. Brown and James E. HutchisonView Author Information Department of Chemistry and the Materials Science Institute University of Oregon, Eugene, Oregon 97403-1253 Cite this: J. Am. Chem. Soc. 1999, 121,…
Die einzigartige Struktur von MCM-41-Silicaten (im Bild schematisch dargestellt) bietet äußerst attraktive Eigenschaften: einheitliche Porengrößen von mehr als 20 Å, innere Oberflächen von mehr als 1000 m2 g−1 sowie eine weitreichende Ordnung der Poren. Die Forschung auf dem Gebiet der mit supramolekularen Templaten h…
The electrical properties of dense nanocrystalline TiO2 ceramics with an average grain size of 35 nm were investigated by impedance spectroscopy and compared with a coarsened material with micron size grains. The nanocrystalline ceramics show an uncommon domain of ionic conductivity at high oxygen pressures and a stee…
Solutions of free base meso -tetraphenylporphyrin (H 2 TPP), meso -tetra(4-carboxyphenyl)porphyrin (H 2 TPPC), and meso -tetra(4-pyridyl)porphyrin (H 2 TPyP) under various conditions generate aggregates whose absorption spectra are characterized by invariant Soret bands with bandwidths that are independent of the prep…
The so-called “total yield” approach often fails to explain the measured sign of the surface potential, VS, and the shift of the nominal critical energy EC2∘ (where δ°+η°=1) of electron irradiated insulators. Here, a simple modification of this approach consists in including some extra interactions of the secondary an…
By means of an effective potential associated with a constrained equilibrium measure and apt to study frozen systems, we investigate glassy freezing in simple liquids in the hypernetted chain (HNC) approximation. Unlike other classical approximations of liquid theory, freezing is naturally embedded in the HNC approxim…
Several crystal structures of tungsten trioxide have been studied with a first-principles pseudopotential method. The electronic band gap increases significantly with the distortion of the octahedra that are the building blocks of the various crystal structures. Moreover, the tilting of the octahedra in the more compl…
A first-principles study of the birefringence and the frequency-dependent second-harmonic generation (SHG) coefficients of the ternary pnictide semiconductors with formula ${\mathrm{ABC}}_{2}$ $(A=\mathrm{Zn},$ Cd; $B=\mathrm{Si},$ Ge; $C=\mathrm{As},$ P) with the chalcopyrite structures was carried out. The zero-freq…
Using first-principles supercell calculations, we have investigated energetic, structural, and dielectric properties of three different ${A(B}^{\ensuremath{'}}{B}^{\ensuremath{''}}){\mathrm{O}}_{3}$ perovskite alloys: ${\mathrm{B}\mathrm{a}(\mathrm{Z}\mathrm{n}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ (BZN), ${\mat…