Materials Literature
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The postulated low thermal conductivity and the possibility of altering the electronic conductivity of metal-doped clathrates with semiconducting host elements have stimulated great interest in exploring these compounds as promising thermoelectric materials. The electronic and thermal properties of the prototypical Na…
The first five generations of the stilbenoid dendrimers 1(n) (n = 1-5) have been prepared by a combined coupled synthesis (between the generations of the dendrons 8-12) and convergent synthesis. Wittig-Horner reactions together with a protecting group technique yield monodisperse compounds of high constitutional and c…
We report that Co metal nanoparticles (an average diameter of 4 nm) chemically synthesized by a reverse micelle method catalyzes the growth of multiwall carbon nanotubes (MWNTs) aligned perpendicular to a substrate. The surface of the nanoparticles is covered with surfactants so that the nanoparticles can be dispersed…
Electronic properties of heterojunctions between metallic and semiconducting single-wall carbon nanotubes are investigated. Ineffective screening of the long-range Coulomb interaction in one-dimensional nanotube systems drastically modifies the charge transfer phenomena compared to conventional semiconductor heterostr…
The thinnest possible boron polymer strand is found in LiBx (0.82<x<1.0, see picture) and can be described by the two mesomeric forms =[B−=]nB−= or −[B−. The compound LiBx consists of an aligned array of such boron wires embedded in a lithium matrix. Furthermore, each boron atom yields one negative charge and, thus, b…
For a solid in which the interactions have a hard core plus a simple soft repulsive tail we show, using a perturbation theory, that the possible stable crystalline structures give rise to a rich phase behavior. We find two concomitant critical points each corresponding to phase transitions separating bcc and fcc struc…
A bidentate bridging coordination of molecular diiodine has been found for the first time in [Rh2(O2CCF3)4I2]⋅I2, which was obtained by deposition from the vapor phase. An X-ray structure reveals a zigzag chain polymer (shown in the picture) formed by alternating [Rh2(O2CCF3)4] and I2 molecules; another diiodine molec…
Small organic gelling agents very efficiently self-assemble into an entangled network in a wide variety of organic solvents, thereby turning the liquid into a gel. Recent progress in the design of organogelators led to tailor-made gelling agents for supercritical CO2. Furthermore, such agents can be used as templates…
That flexible side groups pointing to the outside are not essential for the formation of discotic liquid crystals is displayed by the structure of 1, in which the rigid core functions as the periphery and the alkyl chains point toward the inside.
In this letter, grain-boundary effects on the electrical transport and the ferromagnetic transition temperature were investigated in La0.8Ca0.2MnO3. The different ferromagnetic transition temperature (45 K) and the different metal–semiconductor transition temperature (62 K) were observed in the samples with different…
We report on the strong blue–violet photoluminescence (PL) at room temperature from the large-scale highly aligned boron carbonitride (BCN) nanofibers synthesized by bias-assisted hot filament chemical vapor deposition. The photoluminescence peak wavelength shifts in the range of 470–390 nm by changing the chemical co…
The influences of low-dielectric interfacial layers on the dielectric properties of Pt/(Ba,Sr)TiO3/Pt capacitors were investigated before and after postannealing. The interfacial layer is believed to be the intrinsic dead layer (low-dielectric layer) due to the termination of chemical bonds of the (Ba,Sr)TiO3 (BST) ma…
We report the fabrication and test results for polymeric electro-optic modulators with a half-wave voltage of 0.8 V and a half-wave voltage-interaction length product of 2.2 V cm. These modulators employ an optical push–pull architecture and are made from poly(methylmethacrylate) with a high molecular hyperpolarizabil…
The remarkable phase behavior for binary mixtures of large-core polynuclear aromatic species and small-core discogens cannot be explained simply in terms of net quadrupolar or charge-transfer interactions. The stable π stacking in these mixtures can instead be rationalized by invoking a complimentary polytopic interac…
Vacancy-related defect profiles have been measured for La0.5Sr0.5CoO3/(Pb0.9La0.1)(Zr0.2Ti0.8)O3/La0.5Sr0.5CoO3 ferroelectric capacitors using a variable-energy positron beam. By varying the layer thickness and the postgrowth processing in a reducing ambient, a capacitor showing oxygen deficiency dominantly in the top…
We have experimentally determined the binding energies of Xe, CH4, and Ne on samples of closed-ended single-wall nanotube (SWNT) bundles. We find values for these quantities which are larger by approximately 75% on the SWNT samples than the values found for the same adsorbates on planar graphite. We have also determin…
Thermal conductivity, resistivity, Seebeck coefficient, and structure measurements of CoSb3 with tin interstitially placed in the voids are reported. These tin-filled skutterudites were synthesized under high pressure and temperature conditions; they cannot be synthesized under “normal” synthesis approaches. The tin a…
This paper assesses the importance of three-body triple dipole interactions for quasi-one dimensional phases of He, Ne, H_2, Ar, Kr and Xe confined within interstitial channels or on the external surfaces of nanotube bundles. We find the substrate-mediated contribution to be substantial: for interstitial H_2 the well…
We present a direct calculation by molecular-dynamics computer simulation of the crystal/melt interfacial free energy, $γ$, for a system of hard spheres of diameter $σ$. The calculation is performed by thermodynamic integration along a reversible path defined by cleaving, using specially constructed movable hard-spher…
How can secondary building units (SBUs) be assembled periodically in three dimensions? An answer is provided by the procedure presented here, in which virtual libraries of inorganic architectures are generated by simulations. The method uses tailored “sticky-atom” potentials, and a simulated annealing–minimization clu…