Materials Literature
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A realistic model of transport properties of zinc oxide ceramic varistors is constructed from two-dimensional Voronoi networks, with a varying degree of disorder, and studied via computer simulations. The relationship between the current-voltage (I-V) characteristic of a single grain boundary and the I-V characteristi…
Band structure calculations and electron paramagnetic resonance measurements are used to show that Pb states determine many of the electronic properties of Pb(Zr,Ti)O3 ferroelectric materials. The valence-band edge consists of hybridized Pb s and O p states at all compositions. The conduction-band minimum changes from…
Lattice cells containing point defects in ferroelectric single crystals can behave as a second phase. In addition to the role these defects have in the variation of several chemical and physical properties of the ferroelectric, they modify those physical properties of the ferroelectric that are manifested in the hyste…
The design and performance of a new type of high-efficiency diffraction grating for use in either transmission or reflection are described. The gratings are produced in a multilayer dielectric coating deposited upon optically flat substrates. By proper design of the multilayer stack and grating structure, a diffractio…
The photoconductivity of diamonds grown by chemical vapor deposition has been studied in the near infrared and visible spectral regions. The dominant photoconductive response has a threshold at approximately 1.5 eV. There is additional sharp structure in the region extending 165 meV to higher energy from the threshold…
We present a study of the equilibrium properties of sp-bonded solids within the pseudopotential approach, employing recently proposed generalized gradient approximation (GGA) exchange-correlation functionals. We analyze the effects of the gradient corrections on the behavior of the pseudopotentials and discuss possibl…
Optical spectra have been investigated for the prototypical Mott-Hubbard (MH) insulators ${\mathrm{LaTiO}}_{3}$ and ${\mathrm{YTiO}}_{3}$, and their solid solutions ${\mathrm{La}}_{\mathit{x}}$${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{TiO}}_{3}$. The MH gap shows a critical variation with x or equiv…
We present first-principles local-density band structure calculations for one-dimensional and three-dimensional crystalline poly (para-phenylene) (PPP) using the full-potential linearized augmented-plane-wave and the pseudopotential methods. Optimized structural parameters for PPP chains and for orthorhombic crystalli…
Abstract This work deals with the molecular characterization of maleic anhydride melt‐functionalized polypropylene (PP‐g‐MA). The functionalization mechanism, the nature, the concentration, and the location of grafted anhydride species onto the polypropylene chain are discussed. The polypropylene functionalization was…
The structural stability and electronic properties of the ternary intermetallic compounds NiSnM (M=Ti,Zr,Hf) and the closely related Heusler compounds ${\mathrm{Ni}}_{2}$SnM are discussed using the results of ab initio pseudopotential total-energy and band-structure calculations performed with a plane-wave basis set u…
Single crystals of the skutterudite ${\mathrm{CoSb}}_{3}$ exhibit large hole mobilities (up to 3000 ${\mathrm{cm}}^{2}$ ${\mathrm{V}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ at room temperature), intrinsic lattice thermal conductivity down to 10 K, and pronounced phonon drag effects in th…
We report the successful synthesis of ${\mathrm{B}}_{\mathit{x}}$${\mathrm{C}}_{\mathit{y}}$${\mathrm{N}}_{\mathit{z}}$ nanotubes. Arc-discharge methods were used to produce stable nanotubule structures identified by high-resolution transmission-electron microscopy. Local electron-energy-loss spectroscopy of K-edge ab…
We have measured the dielectric relaxation times of the α process of phenyl salicylate (salol) covering 11 decades in frequency. Being representative for the class of low molecular weight organic glass forming materials, the highly resolved temperature dependence of the dynamics in salol does not follow a particular f…
The effects of thermal activation on the dislocation emission from an atomistic crack tip are discussed. Molecular dynamics simulations at different constant temperatures are carried out to investigate the thermal effects. The simulated results show that the processes of the partial dislocation generation and emission…
The alternating current conductivity of Li 0.5+0.5x Ge x Fe 2 O 4 (where x=0.0, 0.2, 0.3 and 0.5) has been studied as a function of frequency, whereby the conductivity showed a dispersion with respect to frequency. In the range of dispersion it was found that sigma ( omega ) alpha omega S , where S is a constant. At f…
The source characteristics of third-generation synchrotron radiation machines lead to enhanced possibilities for diffraction topographic techniques: real-time observations, high-resolution experiments, investigation of heavy or bulky materials using short wavelengths and the possibility of using large sample environme…
The elucidation of the structure of semiconductor multilayers can be adequately determined by X-ray methods but the interpretation is not always straightforward. In this paper we introduce the idea of full three-dimensional diffraction-space mapping to obtain information on the three-dimensional structure of imperfect…
X-ray projection reflection topography has been applied to a number of strongly absorbing crystals in order to find general rules for rendering dislocations visible. Single- and double-crystal schemes have been utilized. Considering direct images of dislocations and calculating the ratio of extinction to the absorptio…
Variations in the band structures of C60-polymers are studied, when pi-conjugation conditions are changed. We look at band structures in order to discuss a metal-insulator transition, using a semi-empirical model with the Su-Schrieffer-Heeger type electron-phonon interactions. We find that electronic structures change…
Self-diffusion coefficients of a series of polycyclic charged systems and their parent compounds were measured by using the PGSE NMR method. These data suggest that the dianions of naphthacene 2 and pyracylene 3 may exist as dimers with sandwich structure, just like the lithium salt of the tetraanion of corannulene 1.