Inhomogeneous thermoelectrics
Theoretical calculations show that inhomogeneous doping can increase the efficiency of thermoelectric generators and refrigerators.
Materials Literature
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Magnetic properties of Fe deposited into anodic aluminum oxide pores as a function of particle size
A combination of magnetic and electron microscopic measurements on iron deposited in chemically widened anodic aluminum oxide films has allowed us to relate the coercivity of these materials to the dimensions of the metal particles. The coercivity is found to be highly anisotropic and to depend on the aspect ratio of…
Porous vycor glass: The microstructure as probed by electron microscopy, direct energy transfer, small-angle scattering, and molecular adsorption
We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small-angle x-ray scattering, molecular adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is prese…
Enhanced order and electronic delocalization in conjugated polymers oriented by gel processing in polyethylene
We report the polarized absorption ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{\ensuremath{\theta}}}$(\ensuremath{\Elzxh}\ensuremath{\omega}) and photoluminescence ${\mathit{L}}_{\mathrm{\ensuremath{\theta}}}$(\ensuremath{\Elzxh}\ensuremath{\omega}) spectra of gel-processed blends of poly(2-methoxy,5-(2'-ethyl-hexoxy)-p-…
Self-consistently determined properties of solids without band-structure calculations
We propose an approach to the calculation of the cohesive and the structural properties of solids. This approach is based on the second theorem of Hohenberg and Kohn and allows one to obtain directly the charge density and the total energy without determining, at the same time, the band structure of the system. The me…
Calculation of ground-state and optical properties of boron nitrides in the hexagonal, cubic, and wurtzite structures
The electronic structures, the charge-density distribution, and the total energies of boron nitrides (BN) in the hexagonal, cubic, and wurtzite structures are studied by first-principles self-consistent local-density calculations. For the ground-state properties, the band structures, the equilibrium lattice constants,…
Spin-Polarized Photoemission from f.c.c.-Cobalt above the Curie Temperature: Evidence of Short-Range Magnetic Order
We report on the first spin- and momentum-resolved photoemission studies on epitaxial f.c.c.-cobalt films above the Curie temperature. In order to obtain a thorough characterization of the electronic states, the photoelectrons have been excited by circularly polarized VUV synchrotron radiation and a vectorial spin ana…
Pyroelectric properties of Bi2VO5.5ceramic
The dielectric, pyroelectric and thermal properties of ferroelectric Bi 2 VO 5.5 (Bi 4 V 2 O 11 ) ceramic have been studied over a temperature range of 300-780 K. The sign of the pyroelectric coefficient is positive at room temperature. The dielectric constant, pyroelectric coefficient and specific heat exhibit anomal…
Self-trapping holes and excitons in the bulk and on the (100) surfaces of MgO
Self-trapping of holes and excitons in the bulk and on the surface of MgO has been simulated using the self-consistent semi-empirical intermediate neglect of differential overlap method within an embedded molecular cluster model. The authors results suggest that, while holes are not self-trapped in the bulk of MgO, th…
FTIR characterization of triclinic lead phthalocyanine
Infrared absorption spectra are presented for freshly evaporated lead phthalocyanine, oxygen doped lead phthalocyanine and material which has been vacuum annealed. The spectra allow characterization of films for utilization in gas sensors and FET structures.
Characterization of K2Ca2(SO4)3:Eu phosphor
A new phosphor, K 2 Ca 2 (SO 4 ) 3 :Eu, which is more sensitive than the widely used CaSO 4 :Dy has been recently reported. In this paper the authors present results which demonstrate the effect of various preparation procedures on thermoluminescence sensitivity, including the valence state of the impurity and its pos…
Magnetic spin-lattice relaxation in nuclear quadrupole resonance: the eta not=0 case
The authors give solutions for spin-lattice relaxation in NQR due to magnetic interactions, generalized for non-axial crystal fields with eta not=0. They find analytic expressions for I=3/2 and give numerical solutions for I=5/2, 7/2 and 9/2. They find that the relaxation curves change considerably with eta . Specific…
Scattering of light from a two-dimensional array of spherical particles on a substrate
The authors present a method for the calculation of the scattering of light by a periodic two-dimensional array of spherical particles adsorbed on a uniform dielectric slab. Multiple scattering of light between the particles of the overlayer and between the overlayer and the substrate is taken fully into account. The…
Liquid crystal phase diagram of the Gay-Berne fluid
In this paper we report computer simulation results for bulk Gay-Berne fluids with anisotropy parameters κ = 3 and κ′ = 5. Using molecular dynamics simulations in the NVT ensemble, we identify isotropic fluid, nematic and smectic B phases. We observe that the nematic phase is only stable for reduced temperatures T* >…
Low-energy heavy-ion irradiations of copper and molybdenum at low temperatures
Abstract A specially designed and characterized oil-free cryogenic UHV experimental system has been used to irradiate pre-thinned orientated copper and molybdenum single crystals at 4.2 and 78 K with very high doses (5 x 1012 to 5 x 1015 ions cm-2) of low-energy (0.2-20 keV) self-ions and xenon ions. Populations of di…
Latent hardening in single crystals. II. Analytical characterization and predictions
Abstract Constitutive equations are developed that characterize the multiple-slip behaviour of crystalline materials at low temperature. A matrix of instantaneous hardening moduli that relate the rate of hardening on each slip system to all slip-rates is proposed based upon well-known observations and the latent harde…
Transport in ionic conducting glasses
The frequency-dependent conductivity of glasses is explained in a treatment spanning the range of frequencies, 0< omega < nu ph approximately=10 12 Hz. A large spread of individual relaxation times is assumed. The connection between low frequency AC conduction and DC conduction is their common origin in non-local rela…
Absorption redshift in TiO2 ultrafine particles with surfacial dipole layer
It is found that the TiO2 ultrafine particles (UFP) coated with a layer of stearic acid radicals had a significant red shift of their absorption band edge and clear photoluminescence at room temperature (RT), which are in contrast with that of bulk TiO2 and naked TiO2 UFP. It was concluded that these results are relat…
Quasiperiodic tilings with tenfold symmetry and equivalence with respect to local derivability
Two 2D quasiperiodic tilings with generalized tenfold symmetry are derived from the lattice A 4 R , the reciprocal of the root lattice A 4 . Both tilings are built from four tiles, triangles in one case, rhombi and hexagons in the other. After a brief description of the tilings and their structures, the authors introd…
Analysis of and Solutions to the CaCO3 and CaSO4 Scaling Problems Encountered in Wells Offshore Indonesia
ABSTRACT Pertamina/MAXUS Southeast Sumatra Petroleum, Inc. is the largest offshore oil producer in Indonesia. CaCO3 and CaSO4 scaling in and around the submersible pumps of Pertamina/MAXUS' Farida/Zelda reservoir wells led to premature pump failures and costly workovers to bring the wells back into production. Twenty-…