Materials Literature
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Single-crystal metallic cubic sodium-tungsten bronzes ${\mathrm{Na}}_{\mathit{x}}$${\mathrm{WO}}_{3}$ (x\ensuremath{\ge}0.25) and ${\mathrm{Na}}_{\mathit{x}}$${\mathrm{Ta}}_{\mathit{y}}$${\mathrm{W}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{O}}_{3}$ (x-y=0.42) and monoclinic reduced ${\mathrm{WO}}_{3\mathrm{\ens…
Dielectric dispersion was observed in a single crystal with the composition of ErFe 2 O 3.95 below magnetic transition temperature. It is characterized by a large dielectric constant of the order of 10 4 , and a Debye-type frequency dependence like in the polycrystalline samples of the same substance which we reported…
Electronic structures of the Heusler compounds, NiMnSb and PtMnSb, are investigated by using the linearized-muffin-tin-orbital band method. Equilibrium properties such as lattice constants and bulk moduli are obtained from total energy calculations and effects of the spin-orbit interaction on electronic structures and…
The influence of hydrogen incorporation on the microstructure of hydrogenated amorphous carbon (a-C:H) films has been studied in detail by applying several complementary methods, i.e., elastic recoil detection analysis (ERDA), hydrogen evolution, and infrared absorption measurements, to two series of samples prepared…
Ferroelectric lead zirconate titanate thin films of morphotropic phase boundary composition were fabricated through the sol-gel spin-on technique to study the thickness dependence of electrical characteristics. At saturation, the films exhibited a dielectric constant of 1300, dissipation factor of 0.03, Curie temperat…
Scanning tunneling microscopy has been used to investigate the structure of ${\mathrm{TiO}}_{2}$(110) as a function of oxygen-vacancy density. The results are consistent with imaging Ti atoms, as expected given the positive sample bias employed. Our results for the stoichiometric 1\ifmmode\times\else\texttimes\fi{}1 s…
It has been shown in a recent analysis of the temperature dependence of the dc conductivity of the quasi-one-dimensional conductor (fluoranthene${)}_{2}$${\mathrm{PF}}_{6}$ that in spite of the occurrence of the Peierls transition to a charge-density-wave ground state (formally implicating polarons as excitations), th…
The possibility of the existence of a spontaneous relaxor-normal ferroelectric transition was proposed and examined using Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3 (PNN-PT-PZ) pseudoternary system across the morphotropic phase boundary (MPB). On cooling, the PNN-PT-PZ system in the tetragonal-rich side of the MPB underwent a spo…
Modifications of the Helmholtz free energy and the stress associated with general constitutive equations of a simple continuum are proposed to model dispersive effects of an inherent material characteristic length. These modifications do not alter the usual restrictions on the unmodified constitutive equations imposed…
The complete Raman spectra of carbon tubules at various temperatures are compared with those of graphite and fullerene ${\mathrm{C}}_{60}$. The band at 1470 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ as well as those in the range 100--600 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in tubules attest to the presence of…
Electronic structures of ${\mathrm{SrTiO}}_{3}$ (001) surfaces are calculated by the use of self-consistent pseudopotential method with plane-wave basis. The effect of surface defects, which are introduced by removing a surface oxygen in a 1\ifmmode\times\else\texttimes\fi{}1 or a \ensuremath{\surd}2 \ifmmode\times\el…
Amorphous selenium (a-Se) is a photoconductor used for both optical and x-ray imaging. Its optical photogeneration efficiency has been understood in terms of the Onsager theory of geminate recombination. However, x-ray photogeneration in a-Se has not been understood well. A previous argument has dismissed the Onsager…
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…