Materials Literature
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We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with…
In this Brief Report, we present an algorithm for calculating the elastic Lattice Greens Function of a regular lattice, in which defects are created by removing lattice points. The method is computationally efficient, since the required matrix operations are on matrices that scale with the size of the defect subspace,…
In this paper, we present an algorithm for the solution of the von Karman equations of elasticity theory and related problems. Our method of successive reconditioning is able to avoid convergence problems at any ratio of the nonlinear streching and the pure bending energies. We illustrate the power of the method by nu…
The transport properties of an ionic model for liquid silica at high temperatures and pressure are investigated using molecular dynamics simulations. With increasing pressure, a clear change from "strong" to "fragile" behaviour (according to Angell's classification of glass-forming liquids) is observed, albeit only on…
The coalescence of diamond grains grown by microwave plasma chemical vapor deposition was observed at an atomic level using high resolution electron microscopy in combination with scanning electron microscopy. It was shown that large diamond crystals can be grown either by a coalescence of two [001]-oriented grains wh…
Eu2+ ions were incorporated in SiO2 and Al2O3–SiO2 glasses using a sol-gel process of Si(OC2H5)4, Al(OC4H9sec)3, and EuCl3 6H2O. Glasses incorporated with the Eu2+ ions showed the emission with peak at ∼22000 cm−1 due to 4f 6 5d→4f 7(8S7/2) transition of the Eu2+ ions. 1Al2O3⋅99SiO2 (mol %) glass had an intense emissi…
A new class of photodetectors is proposed, based on localized heating of an ultrathin metallic film due to absorption of individual photons. For a 1 eV photon, the transient temperature rise can be of order 10 K or greater in a nonequilibrium ‘‘hotspot’’ on the nm spatial scale and ps timescale. If current is flowing…
Low temperature two-photon fluorescence excitation microscopy was used to obtain fluorescence spectra of single CdSe colloidal nanocrystals or quantum dots. The fluorescence spectra reveal large, 0.02 eV shifts of the peak emission wavelength on times of the order of 100 s were also observed in some instances. We attr…
It has been shown that the blue photoluminescence (PL) of porous silicon (PS) can be obtained simply from postanodization illumination by white light without any oxidation processes. The PS samples were formed on 5–6 Ω cm p-type (100) Si wafers. The anodization was carried out in an ethanoic HF solution at a current d…
We report the formation of self-assembling CdSe quantum dots during molecular beam epitaxial growth on ZnSe and ZnMnSe. Atomic force microscopy measurements on specimens with uncapped dots show relatively narrow dot size distributions, with typical dot diameters of 40±5 nm, and with a diameter-to-height ratio consiste…
The title radicals, C19H14N3, are arranged in columns along the b axis, in which the almost planar 1,2,4-triazin-4(1H)-yl ring and the phenyl ring on C3 of adjacent molecules lie alternately on top of one another. Within the array, the mean interplanar distance is 3.45 Å. However, the centers of the 1,2,4-triazin-4(1…
Static and dynamic dielectric properties were studied around the ferroelectric phase transition temperatures of PbHAsO 4 and PbHPO 4 . Typical Debye-type dielectric dispersions were observed in both of the ferroelectrics. Dynamic dielectric properties of the two ferroelectrics are very similar to each other. On the ot…
The elastic free energy of carbon nanotubes grown by iron-catalyzed decomposition of acetylene is introduced to describe the possible tubular shapes. The equilibrium shape equation can be obtained by the first variation of the elastic free energy of the slightly distorted tube. The model is consistent with both stable…
We present results of high-pressure--low-temperature studies of template synthesized polypyrrole. Thermopower measurements at ambient pressure show a linear temperature dependence, which supports the intrinsic metallic character of the samples. The dc conductivity follows the typical variable-range-hopping behavior at…
A theory for resistivity and magnetoresistance of ${\mathrm{LaMnO}}_{3}$-type degenerate ferromagnetic semiconductors is developed. The peak of resistivity not far from the Curie point ${\mathit{T}}_{\mathit{C}}$, which is absent in perfect crystals, is explained by a magnetization-dependent impurity scattering when t…
The title compound, μ-[(E)-1,3-di-η5-cyclopentadienyl-2-buten-1-one]bis(η5-cyclopentadienyliron) –Water (4/1), [Fe2(C5H5)2(C14H12O)].0.25H2O, has two independent [Fe2(C5H5)2(C14H12O)] molecules in the asymmetric unit. Pairs of one of these molecules form dimers linked by hydrogen bonds via a water molecule occupying e…
The effects of surface-tension anisotropy on interface morphology during the directional solidification of a binary alloy are studied. The long-wave evolution equation derived by Brattkus & Davis to describe growth near the absolute stability limit is generalized to include the effects of a surface tension wit…
Optical absorption, photoluminescence (PL), and electron paramagnetic resonance (EPR) data on unirradiated and UV-irradiated Ge-doped silica are reported. The analysis of the UV-induced effects shows the following facts: (i) both components of the 5-eV absorption band are partially bleached, as well as the PL excited…
The transient induced absorption and bleaching are examined in 10 nm size CuS nanocrystals embedded in polyvinylalcohol film. Partial surface oxidation of CuS nanocrystals produces a new near-IR-absorption band peaked at 1100 nm. The surface oxidized shell is supposed to form a midgap electron acceptor level and the n…
We have carried out a systematic search for the lowest energy structures of (AlP)N (N⩽6) clusters using density functional theory within the local density approximation. We employ a novel search strategy based on genetic algorithm to find the global minima of these clusters. This study reveals that (AlP)N alloy cluste…