Materials Literature
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Starting from an atomistic sterical hindrance potential, translational and orientational motion of the N${\mathrm{O}}_{2}$ group in the deformable lattice are described. The reorientations of the N${\mathrm{O}}_{2}$ group in the paraelectric phase occur essentially by rotations around the crystallographic $\stackrel{\…
Dispersing coarse grains of Al2O3 in a fine-grained matrix of the same material a bending strength of about 500 MPa and fracture toughness of 8 MPa m1/2 are realized on conventionally as-sintered specimens. The improved mechanical properties of the bidisperse structure can be explained by residual stress initiated mic…
Complex admittance measurements are performed on high-purity ceramics prepared by means of the alkoxide synthesis and on less pure ceramics obtained from the citrate synthesis. The results on ceramic materials with grain sizes ranging from 0.4 to 20 μm are compared with those from a single crystal. The activation enth…
As an extension of Table 7.1.5B of International Tables for X-ray Crystallography [(1967), Vol. II. Birmingham: Kynoch Press], the possible stacking variants up to ten layers are arranged according to the percentage of hexagonal stacking. A method is given which allows one to calculate the number of possible stacking…
On the basis of the available force fields for the S8 ring the vibrational Raman intensities of an α-S8 single crystal and of a randomly oriented polycrystalline sample are interpreted in the frame of the bond polarizability model. The whole set of Raman tensors of the S8-molecular ring and of the single crystal inclu…
The surface-enhanced Raman spectrum of CO adsorbed on colloidal silver particles of about 100 Å diameter is reported. The spectrum resembles that observed for CO adsorbed on vapor-deposited silver. Only three strong Raman lines appear, at 2113, 160, and 64 cm−1. These are assigned, respectively, to the CO stretching,…
The fluorescence spectrum of ${\mathrm{Eu}}^{3+}$ in monoclinic ${\mathrm{Gd}}_{2}$${\mathrm{O}}_{3}$ is analyzed at 300, 77, and 4.2 K. There are three distinct ${C}_{s}$ crystallographic sites for the rare earth in the monoclinic structure. Through selective excitation of the three $^{5}D_{0}$ levels with a dye lase…
A theory of lattice thermal conductivity is formulated in which phonons are divided into propagating and reservoir groups. At high temperatures, the groups are differentiated according to whether they occupy nondispersive modes below or dispersive modes above the U-process combination frequency threshold. Below this t…
Transparent heat mirrors of the antireflecting metal type with a dielectric/metal/dielectric structure are studied. It is found that dielectrics of lower refractive index give a higher cutoff wavelength, but the transition becomes more gradual. The angular behavior of these mirrors is also analyzed. The optimum mechan…
The wave number dependence of the diffusion coefficient measured by dynamic light scattering is predicted in the dilute limit through a relatively simple, but rigorous, equilibrium analysis of the diffusion process. For hard sphere interactions with ak≲0.2 the gradient diffusion coefficient should be detected, but for…
Photoluminescence spectra of undoped crystals of the layer semiconductor GaSe have been measured from 80 K up to room temperature. The direct and indirect excitonic emissions are clearly observed in the intrinsic part of the spectrum. Moreover, a detailed analysis of the luminescence intensity has been made as a funct…
A method is described to derive average atomic-displacement energies from damage-rate measurements on polycrystalline materials under electron irradiation. The results for several cubic metals are compared to data obtained from electron irradiations of single crystals and to effective displacement energies derived fro…
The Raman spectra of trans-polyacetylene excited with various laser wavelength (4579, 4880, 5145, 5682, and 6471 Å) show the lines at 1100 cm−1, 1500 cm−1 in (CH)x, and 860 cm−1 and 1400 cm−1 in (CD)x broadened. From a valence-force-field calculation of the optical modes, force constants in agreement with results from…
Detailed studies of the pressure and temperature dependences of the ionic conductivities of TlCl and TlBr have allowed determination of the lattice volume relaxations and energies associated with the formation and motion of Schottky defects in these crystals. The volume relaxations deduced from the conductivity are fo…
The magnetic susceptibility of the layered compound V${\mathrm{Se}}_{2}$ is known to be very sensitive to preparation conditions. Preparation at temperatures above 580\ifmmode^\circ\else\textdegree\fi{}C produces interstitial (intercalated) V atoms that induce a paramagnetic moment and a Curie contribution to the susc…
Optical absorption and thermoluminescence spectra of nominally pure X-irradiated KDP have been obtained between 13K and room temperature. Absorption spectra and their associated thermal bleaching curves exhibit a strong dichroism. Two glow peaks are observed at 73K and 123K which correlate well with main decay steps o…
The collective translational structure of dilute suspensions (\ensuremath{\sim} 0.1% by weight) of charged, spherical, and colloidal particles under shear is investigated by light scattering. When subjected to increasing shear rate, the equilibrium bcc Wigner lattice exhibits two major, reversible, disordering transit…
The temperature dependences of the c axis thermal expansion and elastic constant c 44 have been measured in single-crystal samples of dysprosium between the Neel temperature T N and Curie temperature T C . Anomalous behaviour is observed at several temperatures in the range T C <T<T N , and the anomalies are attribute…
The temperature-induced high-spin(HS)-low-spin(LS) transition of the 3d 4 -3d 7 transition-metal ions in crystals (oxides and sulphides) are investigated on a semiquantitative basis by taking into account the elastic interaction between HS (or LS) clusters produced in a LS (or HS) crystal. The critical temperature at…
A neutral protease has been extracted from the media of cultured metastatic tumor cells and purified approximately 1000 times after sequential ammonium sulfate fractionization, concanavalin A column chromatography, and molecular sieve chromatography. The protease has an apparent molecular weight of 70 000--80 000, is…