Materials Literature
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By ultrasonic methods the elastic constants of V, Nb, and Ta are determined at room temperature after loading with hydrogen and deuterium. For Nb and Ta also the change of the temperature dependence of the elastic constants on alloying are determined up to 300°C. All measurements are performed in the cubic α-phases. T…
The perovskite-type layer structure compound (CH3NH3)2CdCl4 exhibits an unusual phase sequence:
Hyperfine coupling elements, energy levels, and ESR transition frequencies have been computed for the methyl radical taking into account the large anisotropy of the proton hyperfine couplings. The interpretation of low-temperature ESR and ENDOR spectra of methyl radical is discussed with particular attention to the tu…
The optical spectra of single crystals of Cs2NaPrCl6 are reported. A complete f2 analysis gives the parameters: F2=302.0 cm−1, F4/F2=0.1600, F6/F2=0.01596, ξ4f=754.8 cm−1, α=19. cm−1, A4〈r4〉=288.6 cm−1 and A6〈r6〉=39.6 cm−1. A comparison of these parameters with those of the free Pr+3 ion indicates a covalency of 3%. T…
Frozen aqueous solutions (FAS) of Fe3+ salts have been investigated by use of Mössbauer spectroscopy in order to study the conditions for formation of glasses. A general discussion of spin–spin relaxation in glasses is given, and we discuss how changes in the spin–spin relaxation time can be attributed to changes in t…
The reflectivity of single-crystal, orthorhombic GeS has been measured at 300\ifmmode^\circ\else\textdegree\fi{}K for all three polarizations in the photon energy range 0.1-30 eV. Eleven distinct peaks or shoulders are observed, about half of which can be associated with known structure in the valence-band density of…
Cu 50- x Ni x Zn 50 β phase alloys undergo a martensitic transformation from the CsCl-type ordered cubic (B2 structure) to the AuCuI-type tetragonal (Li 0 structure). The martensite L1 0 phase appears at room temperature when Ni composition x becomes larger than 32.5 at.%, i.e. when electron atom ratio ( e / a ) becom…
The intensity, frequency shift, and linewidth of the longitudinal Brillouin lines have been measured from 4 to 300 K in crystal quartz, fused quartz, and borosilicate glass. Differences in intensity between Stokes and anti-Stokes components have been found, extending to low temperatures the observation of long-lived v…
A selective laser excitation technique has been used to study energy transfer between the individual ions of specific crystallographic sites in charge compensated CaF2:Er3+. Unique energy transfer rates have been obtained directly from the fluorescent transients of the selectively excited sites. No energy transfer pro…
An SCF method is derived for doublet states with one vacancy in an orbital within the occupied manifold (hole states). This method gives an upper bound to an excited state energy. Hence it is a stable procedure which is bounded from below and cannot collapse to a lower energy SCF state. This new procedure is compared…
The potential, charge density, energy spectrum, and occupied surface density of states are calculated selfconsistently for two currently popular structural models of the stable 2 \ifmmode\times\else\texttimes\fi{} 1 reconstruction of the Si (100) surface. The features which emerge are discussed in terms of their relat…
X-ray and electron beam diffraction analyses have been carried out on thin films deposited from a beam of carbon ions. Results show that the films consist of a polycrystalline background of cubic diamond with a particle size of 50–100 Å with single-crystal regions up to 5 μm in diameter.
An empirical nonlocal pseudopotential scheme is employed to calculate the electronic structure of eleven semiconductors: Si, Ge, $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$, GaP, GaAs, GaSb, InP, InAs, InSb, ZnSe, and CdTe. Band structures, reflectivity spectra, electronic densities of states, and valence charge de…
High-resolution x-ray-photoemitted valence-electron spectra from a gold single crystal are found to exhibit significant differences for electron emission along various low-index directions, with $〈100〉$ and $〈111〉$ showing the most pronounced dissimilarities. Direct-transition-model calculations predict that such spec…
The impact properties of composites of glass fibre or carbon fibre in polyester or epoxy resin were studied. Impact was by high-velocity water jets ( approximately 700 ms -1 ), which previous work has shown successfully simulate rain erosion damage and other impact situations involving high-stress (of the order of 1 G…
Abstract Cellulose ion exchangers with particles of spherical shape were prepared via chemical transformations of bead cellulose. The products were characterized by measuring their exchange capacity, swelling and by elemental analysis. The spherical shape of the particles was not distorted by chemical reactions. The f…
It is shown that recently reported two-electron, one-photon $K$---x-ray transition energies for collision-excited Fe and Ni ions can be described on the basis of Hartree-Fock calculations, provided that multiple ionic excitation and selection rules for $E1$ transitions are taken into account.
A model calculation shows that each phonon band which couples to the electron density in an organic linear-chain semiconductor effectively develops an infrared activity along the chain axis. The origin of the effect lies in phase oscillations of additional charge-density-wave distortions which inevitably arise in the…
The infrared absorption and the laser excited Raman spectra of BaCl 2 · 2H 2 O powder have been analyzed. The force constants k H and k H governing the librational modes of H 2 O molecules in this crystal are also reported.
Abstract The n.m.r. variable temperature behaviour of the 7‐membered ring in 1,3‐dihydro‐2 H ‐1,5‐benzodiazepin‐2‐one derivatives and in the corresponding 2‐thiones has been investigated. The results indicate that the ring inversion barrier is higher in the thiones and dependent on substituents bonded at N‐1. The acti…