Materials Literature
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The minimum time t required to form an amorphous spot in a crystalline film of Ge2Sb2Te5 with NaCl structure was investigated for various applied laser powers P. An elementary power law of the form P∝t−0.5 is observed for pulse lengths larger than 10 ns which shows that amorphization occurs as soon as the melting temp…
In the past it has been claimed that lamellar molybdenum disulfide ${\mathrm{MoS}}_{2}$ undergoes a deep structural transformation upon lithium intercalation. In the absence of accurate x-ray diffraction data, the structure of ${\mathrm{LiMoS}}_{2}$ is not clearly known, even if recent x-ray absorption spectroscopy re…
We report the synthesis and luminescence decay kinetics of 1.2-nm ${\mathrm{Mn}}^{2+}$-doped ZnS nanoclusters grown in reverse micelles. The preparation method produces small particles with narrow-size distribution and fluorescence bands near 400--450 nm and 585 nm. Time-dependent fluorescence decay measurements using…
Barium titanate $({\mathrm{BaTiO}}_{3})$ ultrafine powders have been prepared from a monomeric metallo-organic precursor through combined solid-state polymerization and pyrolysis. This particular preparation route enables an adjustment of the mean particle size in a wide range from a few nanometers up to micrometer si…
Conductivity and permittivity of the quasi-one-dimensionsional organic transfer salt $(\mathrm{TMTTF}{)}_{2}{\mathrm{PF}}_{6}$ have been measured at low frequencies ${(10}^{3}--{10}^{7}\mathrm{Hz})$ between room temperature down to below the temperature of transition into the spin-Peierls state. We interpret the huge…
Electronic structure calculations of ${\mathrm{LiB}}_{3}{\mathrm{O}}_{5},$ ${\mathrm{CsB}}_{3}{\mathrm{O}}_{5},$ and ${\mathrm{CsLiB}}_{6}{\mathrm{O}}_{10}$ crystals from first principles are performed based on a plane-wave pseudopotential method. The static second-harmonic generation (SHG) coefficients are calculated…
The effect of nitrogen addition on the properties of tetrahedral amorphous carbon (ta-C) has been studied. The ta-C is deposited by a filtered cathodic vacuum arc. The effect of introducing nitrogen on its plasma was measured by a retarding field analyzer and optical emission spectroscopy. The ta-C:N films were studie…
The symmetries of spontaneous lattice distortions in carbon nanotubes are investigated. When the degeneracy of the ground states remains discrete, there are solitons or domain walls connecting the different symmetry-broken vaccua. These solitons, similarly to the case of polyacetelene, are fractionally charged states.…
Molecular-dynamics calculations were performed to simulate ion beam deposition of diamond-like carbon films. Using the computationally efficient analytical potentials of Tersoff and Brenner we are able to simulate more than 103 carbon atom impacts on {111} diamond, so that steady-state film properties can be computed…
The electron and hole addition energies, the quasiparticle gap, and the optical gap of InAs, InP, and Si quantum dots are calculated using microscopic pseudopotential wave functions. The effects of the dielectric mismatch between the quantum dot and the surrounding material are included using a realistic profile for t…
In previous work, we studied the electronic structure of several molybdate and tungstate crystals having the scheelite structure. The wolframite structure is another common form for molybdate and tungstate materials. In this paper, we compare two chemically similar materials that naturally form in the scheelite and wo…
Model calculations are presented that predict whether or not an arbitrary gas experiences significant absorption within carbon nanotubes and/or bundles of nanotubes. The potentials used in these calculations assume a conventional form, based on a sum of two-body interactions with individual carbon atoms; the latter em…
The self-interstitial in diamond produces optical absorption in two narrow lines at 1684.6 and 1859.4 meV. In ${}^{13}\mathrm{C}$ diamond the 1685 meV line shifts by $1.7\ifmmode\pm\else\textpm\fi{}0.2\mathrm{meV}$ to higher energy compared to natural diamond, while the 1859 meV line shifts by $5.35\ifmmode\pm\else\te…
High resolution total and indium differential atomic pair distribution functions (PDFs) for In0.5Ga0.5As alloys have been obtained by high energy and anomalous x-ray diffraction experiments, respectively. The first peak in the total PDF is resolved as a doublet due to the presence of two distinct bond lengths, In–As a…
We have built a database of ab initio total energies for elemental boron in over 60 hypothetical crystal structures of varying coordination Z , such that every atom is equivalent. Fitting to each subset with a particular Z , we extract a classical effective potential, written as a sum over coordination shells and domi…
We use a parametrized linear combination of atomic orbitals calculations to determine the stability, optimum geometry, and electronic properties of nanometer-sized capped graphitic cones, called ``nanohorns.'' Different nanohorn morphologies are considered, which differ in the relative location of the five terminating…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTHigh-Throughput Measurement of Polymer Blend Phase BehaviorJ. Carson Meredith, Alamgir Karim, and Eric J. AmisView Author Information Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 Ci…
Luminescent Eu-containing copolymers were synthesized through the copolymerization of Eu−complex monomers containing β-diketones with methyl methacrylate and characterized by FT-IR, UV−vis, XPS, GPC, TGA, and DSC. All these Eu copolymers are fully soluble in common organic solvents and can be cast into transparent, un…
We report measurements of photoconductivity and electric field induced photoluminescence quenching in three-dimensional close-packed solids of colloidal CdSe quantum dots. Our measurements suggest that photoexcited, quantum confined excitons are ionized by the applied electric field with a rate that depends on both th…
We report total energy and electronic structure calculations for ZnO in the B4 (wurtzite), B3 (zinc blende), B1 (rocksalt), and B2 (CsCl) crystal structures over a range of unit cell volumes. We employed both the local-density approximation (LDA) and the PBE96 form of the generalized gradient approximation (GGA) toget…