Materials Literature
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We calculate the potential energy surface, the low-frequency vibrational modes, and the electronic structure of a (5,5)@(10,10) double-wall carbon nanotube. We find that the weak interwall interaction and changing symmetry cause four pseudogaps to open and close periodically near the Fermi level during the soft librat…
The anomalous resonant behavior of the tangential Raman modes of carbon nanotubes has been studied in the critical region of laser energies 1.7--2.2 eV. The special enhancement of the Raman modes is explained by a model that takes into account the transition between the singularities in the one-dimensional density of…
Recently, it has been reported that doped semiconductor nanoparticles can yield both high luminescence efficiencies and a spectacular lifetime shortening, which suggests that doped semiconductor nanoparticles form a new class of luminescent materials for various applications. From lifetime measurements and time-resolv…
DFT schemes based on conventional and less conventional exchange-correlation (XC) functionals have been employed to determine the polarizability and second hyperpolarizability of π-conjugated polyacetylene chains. These functionals fail in one or more of several ways: (i) the correlation correction to α is either much…
When annealed at elevated temperatures under vacuum, silicon carbide surfaces show a tendency towards graphitization. Using the sensitivity of empty conduction-band states dispersion towards the structural quality of the overlayer, we have used angular-resolved inverse photoemission spectroscopy (KRIPES) to monitor th…
Phase transitions in fluids can be drastically altered by shear flow and heat flow. We briefly discuss the mechanisms of shear effects in three very different fluids. They are near-critical fluids, semidilute polymer solutions in theta solvent, and highly supercooled liquids. As regards heat flow problems, we consider…
We present a high-sensitivity alternating gradient magnetometer. It uses inexpensive, commercially available, piezoelectric quartz tuning fork resonators as vibration amplitude sensors of a vibrating magnetic sample in an alternating gradient field. The technique exploits the high quality factor, high resonant frequen…
An eight-member family of dendrimers has been built up by both convergent and divergent methodologies from an orthogonally-protected amino-tetraacid. Examination of the series by GPC, 1H NMR and computer modeling suggests that the three-directional fourth-generation dendrimer (right) has a globular, void-containing st…
New insights into dendritic boxes: various structural properties for the first five generations of a modified poly(propylene imine) dendrimer are examined. The simulations indicate that cavities, which are partly filled with terminal groups, are present so that guests can be incorporated. It is hypothesised that the l…
Distortions produced in the unit cell of a nonlinear organic crystal under the influence of an applied electric field $E$ are investigated by using synchrotron x-ray multiple diffraction (MD). A typical MD pattern shows numerous $(\mathrm{hkl})$ secondary peaks and the position of each one is basically a function of t…
The oxidation of an Al nanocluster with radius 100 ? placed in oxygen gas at room temperature is investigated by performing molecular dynamics simulations on parallel computers. The simulations take into account the effects of dynamic charge transfer between Al and O on the basis of electronegativity-equalization prin…
We present a well-validated model to predict the roughness on an atomic surface. Surface roughness equation is developed for atomic topography. The root-mean-square roughness σ is found to be proportional to the radii of the surface atoms or ions. Tables are provided for theoretical atomic surface roughness in pure me…
Turnover numbers comparable to those of the enzyme itself in the catalytic epoxidation of alkenes are attained by a supramolecular cytochrome P450 mimic, in which an amphiphilic rhodium complex and a manganese porphyrin are incorporated in a dihexadecyl phosphate vesicle bilayer (shown schematically above). The electr…
We study the electronic properties of a series of tellurides with the antifluorite structure, and (M = Li, Na, K), to reveal the outstanding diffusivity of silver ions. We carry out first-principles density-functional calculations for these systems using the linearized augmented-plane-wave (LAPW) method, where the exc…
A 10-nm-thick PbZr0.25Ti0.75O3 thin film is epitaxially grown on a SrRuO3/BaTiO3/ZrO2/Si heterostructure substrate by reactive evaporation. Structural and electrical properties of the film are investigated. It is concluded that the film is ferroelectric and retains a native uniform upward polarization. Artificial down…
We report calculations of the electronic and magnetic properties of small Co clusters, coated with Ag or Cu, performed with a parametrized tight-binding method. For a given number of Co atoms in a cluster, we obtain a large range of magnetization values, depending on the size and shape of the coating. The noble metal…
Efficient intramolecular energy transfer (ET) from an excited chromophore to Nd3+ and Er3+ ions with subsequent emission in the near-infrared (hν2) is possible in novel compounds (1). These are made by covalent attachment of fluorescein to a calix[4]arene possessing a cavity at the lower rim in which the trivalent lan…
A triblock copolymer that undergoes a thermotropic order-order transition between hexagonally packed cylinders ( $C$) and body-centered-cubic spheres ( $S$) is examined. Transmission electron microscopy provides real space images, and small-angle x-ray scattering the reciprocal space signature, of fluctuations with cu…
Low thresholds (∼500 W/cm2) for amplified spontaneous emission (ASE) are reported in films of soluble poly(paraphenylene vinylene)-based conjugated polymer blends. Efficient Förster energy transfer from the absorbing host polymer to the emitting guest polymer is observed. Emission in the blends originates predominantl…
A single bubble in water is excited by a standing ultrasound wave. At high intensity the bubble starts to emit light. Together with the emitted light pulse, a shock wave is generated in the liquid at collapse time. The time-dependent velocity of the outward-traveling shock is measured with an imaging technique. The pr…