Materials Literature
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Abstract The bonding in tertiary phosphine cluster compounds of gold is sufficiently straightforward to permit an effective interaction between theoretical concepts developed from semi-empirical molecular orbital calculations and synthetic and structural chemistry. At the simplest conceptual level the isolobal nature…
It is shown that phase modulations (phasons) of the order parameters of incommensurate lattices are always diffusive at sufficiently large wavelengths $\ensuremath{\lambda}$. In general there is a crossover from diffusive behavior for $\ensuremath{\lambda}\ensuremath{\gg}\ensuremath{\Lambda}$ to propagating behavior f…
ESR and DC conductivity measurements have been performed on a V 2 O 5 single crystal in the temperature range 4-500K. They suggest that, at low temperature, the unpaired electron remains localised on two vanadium sites associated with an oxygen vacancy, leading to the formation of bound polarons characterised by a 15-…
The results of a synchrotron x-ray study of the crystalline-$B$ to smectic-$A$ melting transition in 4-$n$-pentylbenzenethio-4\ensuremath{'}-$n$-tetradecyloxybenzoate ($\stackrel{-}{14}\mathrm{S}5$) are presented. Samples of two, three, five, and twelve molecular layers were investigated with the freestanding thin-fil…
An extensive analysis of the intermolecular forces in the chlorine crystal has been performed. Different models of the intermolecular potential, including anisotropic terms and electrostatic contributions from multipoles higher than quadrupole have been taken into account and tested for their ability to reproduce stat…
Single crystals of betaine phosphate, (CH3)3NCH2COO · H3PO4, are investigated by dielectric, optic, caloric, and X-ray methods. Besides a structural phase transition at 365 K betaine phosphate shows a transition to an antiferroelectric phase below 86 K. The antiferroelectric state manifests itself by a double hysteres…
Striking differences in the boundary-scattered phonon conductivity and effective phonon mean free path are predicted along the principal axes of cubic crystals. The results are shown to be the result of phonon focusing arising from elastic anisotropy. Normalized curves of boundary-scattered effective phonon mean free…
Abstract Anhydrous solutions of Eu(ClO 4 ) 3 and Eu (NO 3 ) 3 0.05m in N , N ‐dimethyl formamide (DMF) are investigated by means of conductometric measurements, vibrational spectroscopy, electronic absorption and emission spectra, and fluorescence lifetime determinations. Eu (ClO 4 ) 3 is completely dissociated and no…
Dielectric relaxation measurements of undiluted and diluted poly(vinyl acetate) PVAc have been made at temperatures 288<T<366 K over an extremely wide frequency range from 1 μHz to 150 MHz. The complex permittivity can be described quantitatively by the Havriliak–Negami equation ε*=ε∞+Δε[1+(jωτ0)β]−α, 0&…
The concentration dependence of the self-diffusion coefficient Ds has been measured with photon correlation spectroscopy (PCS) from a mixture of two optically distinct hard spherical silica particles in cycloheptane. In the long wavelength limit (K=0), we have found that Ds is a linear function of the particle volume…
The proton line shapes, spin-lattice and rotating-frame relaxation times, and Knight shifts have been measured in crystalline TiCu${\mathrm{H}}_{0.94}$, ${\mathrm{Ti}}_{2}$Cu${\mathrm{H}}_{1.9}$, and ${\mathrm{Ti}}_{2}$Cu${\mathrm{H}}_{2.63}$, and in amorphous $a$-TiCu${\mathrm{H}}_{1.4}$. The second moments of the ri…
The Frank-Condon approach for resonance Raman scattering and optical absorption was used to explain the dispersion effect for the C=C stretch mode in trans-${(\mathrm{CH})}_{x}$ quantitatively. The results are consistent with disturbed and undisturbed areas in the polymer. The Frank-Condon electron-phonon coupling con…
Based on existing periodic models for amorphous Si, a series of random-network models with periodic boundaries have been constructed for amorphous Si${\mathrm{O}}_{2}$ and $\mathrm{Si}{\mathrm{O}}_{x}$, with $x=1.5, 1.0, \mathrm{and} 0.5$. The network structures in which an O atom always bonds to two Si atoms in a bri…
We have generalized simplified small-polaron models for the tunneling of interstitials in solids to include interactions between the diffusing particles. This is applied to the calculation of the average hopping rate of hydrogen in niobium as a function of hydrogen concentration for small concentrations, i.e., for an…
Abstract The preparation of unbranched 4‐alkylbenzaldehydes free of positional and branched‐chain isomers by different methods is described. A one‐step preparation of the aldehydes is reported which involves the ‐direct hydrogenation of a Friedel Craft's complex in the presence of Pd/C catalyst.
Hydrodynamic models of surface plasmons on clean metal surfaces are studied for various choices of additional boundary conditions and of equilibrium electron density profile. Both intrinsic and correctable defects of an approach based on hydrodynamics are illustrated. We conclude that for a clean metal surface, a hydr…
Using semiempirical molecular-orbital calculations, we have obtained the principal transfer integrals which parametrize the band structure of tetramethyltetraselenafulvalene salts [${(\mathrm{TMTSF})}_{2}X$] [$X=\mathrm{Cl}{\mathrm{O}}_{4}, \mathrm{Re}{\mathrm{O}}_{4}, \mathrm{FS}{\mathrm{O}}_{3}, \mathrm{P}{\mathrm{F…
The intrinsic microwave absorption coefficient $\ensuremath{\beta}$ of alkali halides is well explained by lifetime-broadened two-phonon difference processes, in contrast to energy-conserving two- and three-phonon processes as previously thought. A simple closed-form expression for $\ensuremath{\beta}$ with no adjusta…
We discuss the nature of polaron excitations in two models of current interest in the study of quasi-one-dimensional materials: the coupled electron-phonon and molecular-crystal models. Using for definiteness parameters appropriate to trans-${(\mathrm{CH})}_{x}$, we show that, although qualitatively very similar, the…
We have investigated the peroxy-radical defect in glassy Si${\mathrm{O}}_{2}$ by means of MOPN, a semiempirical molecular-orbital program, applied to a cluster of atoms chosen to simulate the defect. Our calculations are consistent with important features of Griscom's model of the defect as a perturbed ${\mathrm{O}}_{…