Materials Literature
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The discrete dipole approximation (DDA), a flexible method for computing scattering of radiation by particles of arbitrary shape, is extended to incorporate the effects of radiative reaction and to allow for possible anisotropy of the dielectric tensor of the material. Formulas are given for the evaluation of extincti…
In many materials with a highly anisotropic band structure, electron-phonon interactions lead to a novel type of ground state called the charge-density wave. The condensate is pinned to the underlying lattice by impurities and by boundary effects, but can, even for small electric fields, carry current in a fashion ori…
For pt.I see ibid., vol.21, p.4795 (1988). Optical absorption spectra under magnetic field and uniaxial stress in (NH 3 (CH 2 ) n NH 3 )MnCl 4 (n=2, 3, 4, 5) were analysed within the framework of a ligand-field approximation. All of the lines that appeared at low temperature are magnon-assisted transitions, and they m…
Optical absorption spectra in the quasi-two-dimensional antiferromagnet (NH 3 (CH 2 ) n NH 3 )MnCl 4 (n=2, 3, 4, 5) were investigated. In the transitions 6 A 1g (S) to 4 A 1g (G), 4 E g (G), 4 T 2g (D), 4 E g (D) and 4 T 1g (P), much fine structure caused by electric dipole transition appeared at low temperature. It w…
Structure factors of dilute binary colloidal suspensions of various compositions, particle diameter ratios and ionic impurity concentrations are investigated using polarised light scattering. For the first time, a split in the second peak of the measured structure factor is observed, suggesting the existence of glass-…
Optical third-harmonic generation was used to measure third-order nonlinear susceptibilities χ(3) for thin films of planar zigzag polysilanes and polygermanes. A χ(3) of 11.3×10−12 esu was measured, the largest value ever reported for a polymer with transparency throughout the visible. The value of χ(3) was found to v…
Abstract Electron diffraction and high-resolution transmission electron microscopy indicate that the radial segments composing coccoliths of the marine alga Emiliania huxleyi are individual single crystalline units of calcite. The top and bottom surfaces of the plate-like lower element correspond to the (12̄10) and (1…
Abstract Mother-of-pearl (nacre) is a platelet-reinforced composite, highly filled with calcium carbonate (aragonite). The Young modulus, determined from beams of a span-to-depth ratio of no less than 15 (a necessary precaution), is of the order of 70 GPa (dry) and 60 GPa (wet), much higher than previously recorded va…
The author considers a quantum Ising model where the exchange couplings and the transverse fields follow a quasiperiodic two-valued sequence. The model is shown to exhibit an Ising-like critical point. The spectrum of the critical Hamiltonian is in accordance with the predictions of conformal theory.
Abstract The effect of several additives such as CaC 2 , CaO, Y 2 O 3 , and C on the thermal conductivity of hot‐pressed AlN ceramics is studied.
Abstract The acid‐catalyzed chemical degradation of polyesters is discussed, with emphasis on the chemistry of the reactions involved. Using primary amines as degrading agents in presence of water as the acid‐ionizing medium, mechanisms consistent with the chemistry of the reaction and those of realted esters are prop…
Linear polarisation, with respect to the z axis, and the effect of the subsequent laser-induced excitation on the luminescence and transient optical absorption induced by irradiation of crystalline SiO 2 with an electron pulse have been studied. It is found that the luminescence spectrum consists of two bands peaked a…
Abstract Polypyrrole–PMMA composite films have been prepared with the chemical oxidative polymerization by spreading the water‐insoluble solvent solution of pyrrole and PMMA mixture on the surface of the aqueous solution containing K 2 S 2 O 8 , the oxidizing agent. The conductivity of the films increases rapidly, pas…
A photoelectron hologram is a two-angle photoelectron diffraction pattern: Direct photoemission plays the role of the reference wave and the scattered waves are the object waves. When the hologram is created from the core-level photoemission of single emitting species on an ordered surface, a complete three-dimensiona…
Transmission electron diffraction and imaging are applied to derive a proposal for the tilt scheme of the perovskite based structure of silver niobate (AgNbO3). Electron diffraction data enable a reduction of the possible spacegroups down to two, each compatible with a number of tilt schemes for the octahedra in the p…
Characteristic features of the dislocation structure developed in the first stage of deformation of single-glide oriented crystals of concentrated f.c.c. alloys like α-CuZn are extended multipoles in the primary slip planes. Their various configurations are explained by considering their formation in the case that the…
It is found with TEM that there is a new phase, called M phase, coexisting with the normal P and Q phases at room temperature. All kinds of ferroelectric domains in the Q phase and antiferroelectric domains in the P phase are observed. They are in good agreement with the results given by the symmetry theory on domains…
Raman scattering measurements were performed to investigate optical modes of scheelite-type double molybdates XY(MoO 4 ) 2 (X=Li, Na and Y=La, Nd). In the polarized Raman scattering measurements, we have found four modes in NaLa(MoO 4 ) 2 , one in low frequency region (with B g symmetry) and three in high frequency re…
We have observed a new, strong feature at 47 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in the first-order Raman spectrum of ion-implanted GaAs, prior to any anneal. It is not present in the Raman spectrum of either amorphous or single-crystal GaAs. The peak is strong between excitation photon energies \ensuremath{\si…
Vapor-grown carbon fibers possessing a high degree of preferential orientation have been prepared using either a catalyzed substrate or a fluidized catalytic method, yielding fibers with diameters of about 10 and 1 μm, respectively. After heat treatment at 2600–2960 °C, the fibers were used as a host material for brom…