Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
A method for determination of lattice parameters of small particles is used which is not an integrale one – in contrast to the commonly employed techniques – and which is utmost sensitive for very small changes in lattice parameters. Thus individual particles can be investigated as well as the variation of lattice par…
The ordering of the trivalent and pentavalent cations in the perovskites Pb(Sc1/2Nb1/2)O3 and Pb(Sc1/2Ta1/2)O3 can be varied by suitable heat treatments. The degree as well as the kind of order strongly affects the character of the FE → PE phase transition. A spatially homogeneous disorder leads to a diffuse phase tra…
Solid state, low temperature IR (25–7400 cm−1) and Raman (100–2600 cm−1) spectra were obtained for Np(BH4)4 and Np(BD4)4 from which most of the allowed fundamentals were assigned based on the Td molecular structure. Those assignments were used in a normal coordinate analysis to derive a simple force field using eight…
Pulsed nuclear quadrupole resonance (NQR) experiments have been performed on three forms of elemental arsenic: amorphous ($a$), rhombohedral ($\mathrm{rh}$), and orthorhombic ($or$). The temperature dependence of the spin-lattice relaxation time (${T}_{1}$) provides evidence for the existence of disorder (tunneling) m…
Dielectric constant and the initial permeability of Fe 3 O 4 have been measured from 4.2 K to room temperature. Magnetic and dielectric relaxations were observed in the temperature range of 30 to 60 K. These relaxations were considered to be caused by the transfer of electron between ferrous and ferric ions. The magne…
Crystalline ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ (orpiment) is a layer-structure semiconductor whose optical properties, under ordinary conditions, are determined by its diperiodic layer symmetry. We have investigated the effect of hydrostatic pressure on the optical-absorption edge and the Raman scattering spectrum…
The incorporation of homovalent ions, e.g., I− in AgBr, leads to a substantial increase in ionic conductivity σ. The charge compensation concept does not explain the enhancement. AgBr+30 mol. % AgI exhibits σ∼7 Ω−1 cm−1 at 380 °C, which is ∼170% larger than that of α-AgI, the best known supersonic conductor, at its me…
The pressure dependence of the Raman peaks of CuGa${\mathrm{S}}_{2}$ and AgGa${\mathrm{S}}_{2}$ (chalcopyrite structure) has been studied up to 20 GPa in a gasketed diamond anvil cell. Nonlinear pressure dependence of several phonon frequencies have been noted, including a softening of the lowest ${\ensuremath{\Gamma}…
The effects of large amplitude shearing rates on 108 particle amorphous Lennard-Jones systems have been examined. A resolution of the structural and dynamical properties reveals that there is a tendency for shear to reorganize the liquid into layers to facilitate flow and hence reduce shear viscosity. The first steps…
A simple phenomenological model is presented for the calculation of intensity of Stokes scattered light due to vibrations of molecules adsorbed on a metallic grating or a rough metal surface. The surface roughness is assumed to be represented by a superposition of sinusoidal gratings of different periodicities, with e…
We discuss the nature of the lattice instability in a highly disordered quasi-one-dimensional conductor, where the electronic states near the Fermi energy are localized in space. The resulting lattice and charge-density distortions are random in space and are frozen. The mathematical and physical similarities of this…
The optical properties of MgCl 2 have been studied by means of reflection spectra in the region from VUV to XUV, absorption spectra in the VUV region, XPS and UPS spectra. In order to interpret the experimental results, the electronic band structure of MgCl 2 has been calculated by means of the tight binding method fo…
The effect of intermolecular interaction on the Raman spectrum of two modes which are in Fermi resonance has been investigated theoretically. The theory includes the resonance exchange of vibrational energy as well as the inter- and intramolecular Fermi coupling interaction and is expected to be a realistic model for…
High-resolution angle-resolved x-ray photoemission (XPS) valence-band spectra from a clean W (001) single crystal have been observed to show strong spectral variations both with electron-emission direction and temperature. The spectral changes with direction are in very good agreement with the predictions of a simple…
A molecular dynamic calculation on vitreous B2O3 reveals a structure in which boron is trigonally coordinated to oxygen. Boron atoms are at the center of approximately regular triangles. The triangles are connected at apices to form a three-dimensional network of interconnected ribbons and sheets. No tendency to form…
A series of molecular-dynamics calculations has been carried out to examine melting in the classical Gaussian core model at reduced density ${\ensuremath{\rho}}^{*}=0.2$. The stable crystal form at this density is body-centered cubic. Thermal equilibrium values of mean-square particle displacement have been evaluated…
The effects of supporting materials (Al 2 O 3 , SiO 2 , TiO 2 ) on the catalytic activity and selectivity of V 2 O 5 in the reduction of NO x with ammonia are reported. The adsorbed state and the reactivity of the surface species were examined by an ir spectroscopy together with volumetric measurements, and the electr…
The quadratic response formalism is used to derive a general expression for the Auger electron current in the limit of high energies of both photo- and Auger electrons. The Auger decay of the initial core hole is treated to all orders in the decay rate. General formulas for the first and second moments of the Auger sp…
Paraphenylene oligomers (biphenyl, p-terphenyl, p-quaterphenyl, p-quinquephenyl, p-sexiphenyl) form electrically conducting complexes with AsF5. Prolonged exposure to AsF5 causes a polymerization of these p-phenylene oligomers to give highly conducting charge-transfer complexes of poly(p-phenylene). Conductivities as…
The optical transition 2 F 7/2 → 2 F 5/2 of Yb 3+ in the antiferromagnet YbCrO 3 has been studied. The exchange splittings for the ground and excited Kramers doublets were observed in the antiferromagnetic state. From the analysis of the splitting of the ground Kramers doublet as a function of applied magnetic field,…