Materials Literature
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Hydride abstraction by triphenylcarbenium cations in the presence of terminal alkynes and alkenes results in hydrosilylation at room temperature on hydride-terminated porous silicon surfaces, leading to alkenyl- and alkyl-terminated surfaces, respectively. A wide range of surface terminations are possible as the react…
The ${D}^{*}$ Raman band of single-wall carbon nanotubes aligned by shear flow in a polymer matrix has been measured as a function of tensile strain. The Raman intensity varies with the optical polarization direction, an effect which is used here to assess the degree of tube alignment. The strain dependence of the Ram…
Transition metal (Me = V, Fe, and Cr) incorporated into MCM-41 mesoporous molecular sieves (Si/Me = 80) have been synthesized by hydrothermal methods and were loaded with TiO 2 utilizing a sol−gel technique. These materials were found (refs 22, 23) to be photoactive for the destruction of organics with visible light.…
Electronic and structural calculations for atomic clusters present many challenges for traditional theoretical methods. While the computational framework for ground-state properties of clusters is relatively well established, calculations for excited states remain difficult. In this paper we implement a linear-respons…
In the framework of the theory of partially fluidized granular flows we study the formation of longitudinal structures observed experimentally by Forterre and Pouliquen in a flow down a rough inclined plane. We show that the formation of longitudinal structures is related to the positive feedback between the fluidizat…
We report on a diluted magnetic semiconductor based on the ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ tetradymite structure doped with very low concentrations of vanadium (1--3 at. %). The anomalous transport behavior and robust magnetic hysteresis loops observed in magnetotransport and magnetic measurements are experimenta…
Abstract Raman spectra of cornetite, libethenite, pseudomalachite, reichenbachite and ludjibaite were obtained at 298 and 77 K using a Raman microprobe in combination with a thermal stage. Raman spectra of cornetite, libethenite and pseudomalachite are different, in line with differences in crystal structure and compo…
The electron-phonon coupling of a theoretically devised carbon phase made by assembling the smallest fullerenes C$_{20}$ is calculated from first principles. The structure consists of C$_{20}$ cages in an {\it fcc} lattice interlinked by two bridging carbon atoms in the interstitial tetrahedral sites ({\it fcc}-C$_{22…
We discuss the effects of hydrostatic pressure on the superconducting properties of MgB$_{2}$ within the framework of Eliashberg theory. By considering the pressure dependences of all parameters appearing in the McMillan formula, we show that the calculated pressure derivative of $T_{c}$ as well as the variation of $T…
We present an overview of recent work on quantum-based atomistic simulation of materials properties in transition metals performed in the Metals and Alloys Group at Lawrence Livermore National Laboratory. Central to much of this effort has been the development, from fundamental quantum mechanics, of robust many-body i…
We examine the performance of various commonly used integration schemes in dissipative particle dynamics simulations. We consider this issue using three different model systems, which characterize a variety of different conditions often studied in simulations. Specifically, we clarify the performance of integration sc…
The first direct observation of charge order of ${\mathrm{Ni}}^{3+{\ensuremath{\delta}}^{\ensuremath{'}}}$ and ${\mathrm{Ni}}^{3\ensuremath{-}\ensuremath{\delta}}$ by resonant x-ray scattering experiments in an epitaxial film of ${\mathrm{NdNiO}}_{3}$ is reported. A quantitative value of $\ensuremath{\delta}+{\ensurem…
Most interpretations of the magnetic coupling J between two unpaired electrons rest upon simple valence models that involve essentially the ferromagnetic direct exchange contribution, Kab, and the antiferromagnetic effect of the delocalization resulting from the interaction between neutral and ionic determinants, tab,…
Large-scale CdS nanowires were achieved by a new, simple, and low cost process based on thermal evaporation of CdS powders under controlled conditions with the presence of Au catalyst. The synthesized CdS nanowires have lengths up to several tens of micrometers and diameters about 60−80 nm. The growth of CdS nanowires…
Spectroscopic, redox, and photochemical behavior of self-assembled donor−acceptor dyads formed by axial coordination of zinc tetraphenylporphyrin, (TPP)Zn, and fulleropyrrolidine bearing either pyridine or imidazole coordinating ligands were investigated. The UV−vis, 1 H NMR, and ESI-mass spectral studies, as well as…
We present the synthesis and structural characterization of a transition metal oxide hydride, LaSrCoO3H0.7, which adopts an unprecedented structure in which oxide chains are bridged by hydride anions to form a two-dimensional extended network. The metal centers are strongly coupled by their bonding with both oxide and…
Abstract The interactions of carbon dioxide and carbon monoxide at moderately high pressures with clean iron surfaces have been studied using x‐ray photoelectron spectroscopy (XPS) and static time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Clean iron surfaces were analysed after exposure to CO 2 or CO gas h…
In cavitation experiments with deuterated acetone, tritium decay activity above background levels was detected. In addition, evidence for neutron emission near 2.5 million electron volts was also observed, as would be expected for deuterium-deuterium fusion. Control experiments with normal acetone did not result in tr…
The luminescence properties of chemically prepared gold nanoclusters, each composed of a 28-atom core and a glutathione (GSH) adsorbate layer consisting of 16 molecules, were investigated. These clusters show a distinct absorption onset at 1.3 eV corresponding to the opening of an electronic gap within the conduction…
The exact solution of Maxwell's equations in the presence of arbitrarily shaped dielectrics is expressed in terms of surface-integral equations evaluated at the interfaces. The electromagnetic field induced by the passage of an external electron is then calculated in terms of self-consistently obtained boundary charge…