Materials Literature
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The kinetics of micelle evolution of diblock copolymers from unimers toward the equilibrium state is studied analytically on the basis of consideration of the kinetic equations. The association/dissociation rate constants for unimer insertion/expulsion and micelle fusion/fission are calculated by applying Kramers' the…
In this paper, we propose a mechanism for the formation of single-wall carbon nanotubes (SWCNT's) focusing on the possible transition state when tube formation is initiated. The model explains the generation of SWCNT's from carbon-metal plasmas as well as by the chemical vapor deposition technique. The model qualitati…
The infrared properties of single-wall carbon nanotubes have been measured over 15--5000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. The sample is a freestanding film composed of purified nanotubes. The temperature dependence of the reflectance is quite small at all temperatures studied (7.8 to 298 K) and no vibration…
We have investigated the dielectric response of a series of {100} fiber-textured (BaxSr1−x)Ti1+yO3+z samples deposited by liquid-source metalorganic chemical vapor deposition onto Pt/SiO2/Si, as a function of the two most commonly varied microstructural parameters: film thickness and Ti nonstoichiometry y. We find tha…
We analyze the influence of defects on conductance, density of states, and localization in ${(N}_{a}{,N}_{a})$ armchair carbon nanotubes within a tight-binding model. Using the transfer-matrix method, we calculate the reflection (related to the conductance) from a sequence of defects and relate its energy dependence n…
We present a noncontact and nondestructive method to measure thermal conductivity in layered materials using micro-Raman scattering. This method was successfully applied to monocrystalline silicon whose thermal conductivity was found to be 63 W/m K at about 550 °C and then applied to porous silicon layers. For a 50 μm…
Infrared reflectance spectroscopy measurements were made on four members of the $M{\mathrm{Fe}}_{4}{\mathrm{P}}_{12}$ family of filled skutterudites, with $M=\mathrm{La},$ Th, Ce, and U. In progressing from $M=\mathrm{La}$ to U the system undergoes a metal-insulator transition. It is shown that, although the filling a…
Laser-arc evaporation of a graphite target has been used to deposit carbon films that exhibit high hardness (45 GPa) and elastic recovery (85%). High-resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS) were subsequently used to study the microstructure and bonding of the resultant layers…
The low-temperature spin dynamics of doped manganites have been analyzed within a tight-binding model, the parameters of which are estimated by mapping the results of ab initio density-functional calculations onto the model. This approach is found to provide a good description of the spin dynamics of the doped mangani…
Distortions of the oxygen sublattice couple to ${e}_{g}$ orbitals of ${\mathrm{Mn}}^{3+}$ and drive a cooperative Jahn-Teller (orbital ordering) transition in ${\mathrm{LaMnO}}_{3}.$ A simple model for this transition is studied. Without further adjustment, the model predicts the shape and stability of small (anti-Jah…
Uniform microcrystalline nickel(II) hydroxide particles have been prepared via the homogeneous alkalinization of nickel(II) nitrate solutions by urea hydrolysis. The nature of the precipitated solids depends on the temperature of synthesis. At ca. 423 K, i.e., under the hydrothermal conditions attained by microwave he…
We provide a straightforward and efficient procedure to combine the local density approximation plus Hubbard U (LDA+U) total-energy functional with the full-potential linearized augmented plane-wave method. A detailed derivation of the LDA+U Kohn-Sham-type equations is presented for the augmented plane-wave basis set,…
The presence of a large permanent dipole moment has important implications on our understanding of nanocrystalline materials. We report the results of dielectric dispersion studies of CdSe, ZnSe, and metal nanocrystals. Due to the polar nature of the wurtzite lattice, a permanent dipole moment may be expected for CdSe…
We fabricated a two-dimensional subwavelength structured (SWS) surface upon a crystal silicon substrate. The SWS surface was patterned by electron beam lithography and etched by an SF(6) fast atom beam. The SWS grating had a conical profile, the period was 150 nm, and the groove was approximately 350 nm deep. The refl…
Melts of ABA triblock copolymer molecules with identical end blocks are examined using self-consistent field theory (SCFT). Phase diagrams are calculated and compared with those of homologous AB diblock copolymers formed by snipping the triblocks in half. This creates additional end segments which decreases the degree…
The role of the metal-oxide interface in determining the spin polarization of electrons tunneling from or into ferromagnetic transition metals in magnetic tunnel junctions is reported. The spin polarization of cobalt in tunnel junctions with an alumina barrier is positive, but it is negative when the barrier is stront…
It is generally accepted that iron is the most important micronutrient used by bacteria. With members of the family Lactobacillae being the only exceptions so far (3), this metal is essential for cellular metabolism, since it is needed as a cofactor for a large number of enzymes (96). However, this element is not easi…
Experimental solubilities are reported for anthracene dissolved in ternary dibutyl ether + 1-propanol + 2,2,4-trimethylpentane, dibutyl ether + 2-propanol + 2,2,4-trimethylpentane, dibutyl ether + 1-butanol + 2,2,4-trimethylpentane, dibutyl ether + 2-butanol + 2,2,4-trimethylpentane, and dibutyl ether + 2-methyl-1-pro…
The surface-enhanced Raman scattering (SERS) intensities for ethanethiol adsorbed on a silver island film have been measured for a variety of annealing conditions over the 15−300 K temperature range. Reversible temperature dependence of the C−S stretching intensities for an unannealed film similar to the case of 1-pro…
The localized-density-matrix method (Yokojima, S.; Chen, G. H. Chem. Phys. Lett . 1998, 292, 379) is employed to simulate the optical responses of very large carbon nanotubes and polyacetylene oligomers containing 10 000 carbon atoms. The Pariser−Parr−Pople Hamiltonian is used to describe the π electrons in these syst…