Materials Literature
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Parameters determining the performance of the crystalline oxides zirconia (ZrO_2) and hafnia (HfO_2) as gate insulators in nanometric Si electronics are estimated via ab initio calculations of the energetics, dielectric properties, and band alignment of bulk and thin-film oxides on Si (001). With their large dielectri…
We present an ab-initio calculation of the electronic affinity of the hypothetical C-46 clathrate by studying its bare and hydrogenated (100) surfaces. We show that such a system shares with the diamond phase a small electronic affinity. Further, contrary to the diamond phase, the possibility of doping endohedrally th…
We have performed a density functional study of fifteen different structural models of the Si(557)-Au surface reconstruction. Here we present a brief summary of the main structural trends obtained for the more favourable models, focusing afterwards in a detailed description of the atomic structure, electronic properti…
In this paper we report the structure of the Li4Ge4 cluster as a function of charge transfer and polarizability. We find that for small charge transfer (Q < 0.5) this cluster has the expected cubic structure: a Ge4 tetrahedron with a Li ion attached at large distance to each face. With increasing charge transfer Q > 0…
We present several ordering mechanisms in diblock copolymers. For temperatures above the order-disorder temperature and in the weak segregation regime, a linear response theory is presented which gives the polymer density in the vicinity of confining flat surfaces. The surfaces are chemically patterned where different…
In this paper we discuss the structure of A4M4 alkali(=A)- tetralide (= M) (= group 14) clusters. Without polarization these polyions consist of a central tetralide tetrahedron with each face capped by an alkali ion. We show that ionic polarization can lead to quite different cluster structures by breaking up of the t…
There is currently a great need for solid state lasers that emit in the infrared. Whether or not conjugated polymers that emit in the IR can be synthesized is an interesting theoretical challenge. We show that the requirement for such a material is that the exciton delocalization in the system be large, such that the…
We investigate the characteristics of electromagnetic wave propagation in uniaxially anisotropic left-handed media. We discuss mainly under what conditions anomalous reflection or refraction shall occur at the interface when propagating waves pass from one isotropic regular medium into another uniaxially anistotropic…
Abstract The crystallization properties of three regioregular poly(3‐alkyl thiophene)s (P3ATs) are studied: poly(3‐hexyl thiophene) (P3HT), poly(3‐octyl thiophene) (P3OT), and poly(3‐dodecyl thiophene) (P3DDT). The morphology of the isothermally crystallized samples is a whisker type. The values of the enthalpy of fus…
The fluorination of purified HiPco single-wall carbon nanotubes to a stoichiometry CF x ( x ⩽ 0.2) followed by pyrolysis of the partially fluorinated nanotubes up to 1000 °C was found to have “cut” the nanotubes to a range of short lengths (average <50 nm). The pyrolysis process was monitored in-situ with TGA-FTIR. Th…
Abstract Three solvents, that is, acetone, acetic acid, and dimethylacetamide (DMAc), with a range of solubility parameter δ, surface tension γ, viscosity η and boiling temperature were used to generate mixtures for electrospinning cellulose acetate (CA) (degree of substitution, DS = 2.45). Although none of these solv…
Carbon nanotubes have been the subject of considerable attention because of their exceptional physical and mechanical properties. These properties observed at the nanoscale have motivated researchers to utilize carbon nanotubes as reinforcement in composite materials. In this research, a micro-scale twin-screw extrude…
Synthesis of carbon nanotubes by chemical vapor deposition over patterned catalyst arrays leads to nanotubes grown from specific sites on surfaces. The growth directions of the nanotubes can be controlled by van der Waals self-assembly forces and applied electric fields. The patterned growth approach is feasible with…
The synthesis of the fluorine-substituted stannasiloxane complex cyclo-Ph 2 Si(OSnt-Bu 2 ) 2 O· t -Bu 2 SnF 2 ( 7 ) is reported, and its molecular structure has been determined by single-crystal X-ray diffraction analysis.
The synthesis of the fluorine-substituted stannasiloxane complex cyclo-Ph2Si(OSnt-Bu2)2O·t-Bu2SnF2 (7) is reported, and its molecular structure has been determined by single-crystal X-ray diffraction analysis.
Solutions of 4-methylphenylurethane of cellulose in N -vinyl pyrrolidinone have been investigated, and a cholesteric mesophase was found above a concentration of 35 wt % of polymer. The selective reflection of light from the cholesteric solutions lies in the visible region of the spectrum and moves from blue toward re…
We evaluate, by means of variational calculations, the bound state energy ${E}_{B}$ of a pair of charges located on the surface of a cylinder, interacting via Coulomb potential $\ensuremath{-}{e}^{2}/r.$ The trial wave function involves three variational parameters. ${E}_{B}$ is obtained as a function of the reduced c…
[structure: see text] An o-allenyl-p-methoxyphenol intermediate (Int) was for the first time proved to be involved in the photochromic reaction of 2,2-di(4-fluorophenyl)-6-methoxy-2H-1-chromene (FC). Transoid-cis (TC) and transoid-trans (TT) photomerocyanines and the intermediate Int are generated by UV irradiation of…
A formalism based on Yeh’s 4 × 4 matrix algebra is developed to model reflectance and transmittance spectra of randomly oriented polycrystalline materials (sintered ceramics or glass ceramics) with arbitrary crystal symmetry provided that the crystallites are larger than the resolution limit of light. It may be applic…
The CO 2 reforming of methane was studied over Pt supported on Al 2 O 3, ZrO 2, and x % ZrO 2 /Al 2 O 3 (1 ≤ x ≤ 20 wt %). The Pt/Al 2 O 3 deactivated very quickly during 20 h onstream at 1073 K and a CH 4 /CO 2 ratio of 1:1, while the catalysts with a ZrO 2 content above 5 wt % presented improved stability during 60…