Materials Literature
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The author shows that in materials with orbital degeneracy, the crystallographic and magnetic structures are strongly connected: the exchange interactions depend on the occupied orbitals, which are related to the crystallographic distortions. In the case of triply degenerate states, they point out the importance of th…
CONTENTS 1. Introduction 551 2. Theoretical models of the semiconductor-metal transition in disordered systems 552 3. Semiconductor-metal transition in molten semiconductors at high temperatures 561 4. Semiconductor-metal transition and criterion for minimal metallic conductivity of melts at T>Tmp 564 5. Metal-semicon…
The absoulte spin susceptibility of As${\mathrm{F}}_{5}$-doped trans-polyacetylene, ${[\mathrm{CH}{(\mathrm{As}{\mathrm{F}}_{5})}_{y}]}_{x}$, was determined by spin resonance techniques for $0.0004<~y<~0.138$. The Curie-law contribution decreases above $y=0.001$ to a level less than 1 ppm in the highly conductin…
A matrix method (valid in the strong-field limit) is described for evaluating the second-order perturbation theory energy levels to be associated with the spin Hamiltonian H s = mu B S.g.B+S.D.S+I.A.S+I.p.I for the most general symmetry conditions. The method is concise and completely avoids the need for introducing E…
Abstract Review: 21 Literaturhinweise vo und HEUER, A. H.; J. Am.
Band representations of space groups are defined and they are used for the symmetry specification of bands in solids. While the symmetry of atomic orbitals is specified around a single center, the band symmetry of a solid is defined with respect to a whole lattice of centers.
The phase diagram of the ternary system potassium laurate-1-decanol-D$_{2}\mathrm{O}$ was studied over concentration ranges where nematic phases are likely to occur. Two uniaxial nematic phases which are separated by a biaxial nematic phase are found. In limited concentration range the following phase sequence may be…
The crystal structure if RbH 2 PO 4 has been determined by neutron diffraction at room temperature and T c +5K in the tetragonal (paraelectric) phase using single-crystal samples. The techniques of constrained refinement and statistical testing have been used to examine carefully the significance of some pertinent str…
SnO 2 single crystals have been grown by use of vapour-phase reaction method. The crystals obtained are characterised by chemical analysis and electrical measurements. The density of the crystals was determined as 6.994+or-0.001 g cm -3 . The thermal conductivity measured is discussed for different orientations of the…
It is shown that the crystal structures of the binary IV-VI compounds can be classified by parameters derived from a Pauli-force model potential, which has previously been used successfully for the octet and suboctet materials (A N B P-N with P=8 and 2<or=P<or=6). Trends in the transverse effective charges, in the hea…
Synthesis of optically active natural carotenoids and structurally related compounds. IV. Synthesis of (3 R , 3′ R , 6′ R )‐lutein The synthesis of (3 R , 3′ R , 6′ R )‐lutein ( 19 ) according to the building principle C 25 +C 15 C 40 is reported utilizing ( R )‐4‐hydroxy‐2,6,6‐trimethyl‐2‐cyclohexen‐1‐one ( 4 ) as a…
The subject of gradient-index optics dates from the 1850s. However, only in the last 10 years has it been possible to design lenses, manufacture materials, measure the properties, and fabricate lens elements. The current status of gradient-index optics is reviewed.
The complex dielectric constant ϵ = ϵ′– jϵ″ of single crystals of squaric acid C4H2O4(H2SQ) was examined at around 100 MHz and between 2 and 8 GHz as a function of temperature. In the GHz range the imaginary part ϵ″ can be well described by the beginning of a monodispersive relaxation, whose relaxation frequency slows…
The anomalous photovoltaic effect referred to here is obtained fro crystals without a centre of symmetry. The spatially oscillatory photovoltaic current is investigated and the photovoltaic coefficients kijk for SbSI and ZnS determined. These coefficients are k31 = 4 × 10−8 Acm/W, k32 = 3 × 10−8 Acm/W, and k33 = (2 to…
The synthesis is described of four new cleavable, photosensitive, heterobifunctional cross-linking reagents for use in examining membrane organization: 4'-azidoazobenzene-4oxysuccinimide ester (1), N-[4-(p-azidophenylazo)benzoyl]-3-aminopropyl-N'-oxysuccinimide ester (2), N-[4-(p-azidophenylazo)benzoyl]-6-aminohexyl-N…
Optical materials for the 8 - 13 micron waveband are discussed and a range of high performance infrared telescopes incorporating chalcogenide glass is described.
The valence states of Fe and the charge compensation by oxygen vacancies of Fe57-doped BaTiO3 are studied by the Mössbauer effect and gravimetry as a function of O2 partial pressure. By preparational and analytical effort, it is ensured that the dopant homogeneously substitutes Ti4+ in the BaTiO3 lattice (up to 1.2 mo…
The perovskites Pb(Sc1/2Nb1/2)O3 and Pb(Sc1/2Ta1/2)O3 can be obtained in a disordered state by means of a synthesis at high temperature (1250 to 1500°C). Ordering of the trivalent and pentavalent ions occurs during annealing at lower temperatures. The kinetics of this ordering process are investigated by means of X-ra…
Electro-optical measurements of the electric field along solid insulator/vacuum interfaces have been made to determine the mechanisms associated with fast (ns) insulator flashover. Data showing the temporal and spatial performance of the insulator surface fields prior to and at flashover are presented. The results sho…
By modifying the surface plasma mode on a bare metal surface with an ultrathin film deposited on the metal, we measured the film thickness by attenuated total reflection (ATR). Various factors causing measurement errors are estimated with numerical examples. As a result, for example, it is shown that for some thicknes…