Materials Literature
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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic exchange in transition metal complexes. V. Ferromagnetic spin coupling in a tetranuclear nickel(II) clusterAlvin P. Ginsberg, J. Aaron Bertrand, Roy I. Kaplan, C. E. Kirkwood, Raymond Leslie Martin, and Richard C. SherwoodCite this: Inorg. Chem. 1971, 10, 2, 240–246…
The molecular properties of optically active molecules are used to extend the molecular statistical theory of the nematic phase in order to explain the helical structure of the cholesteric phase. In order to account for these properties the dispersion energy between two molecules is calcualted taking into account not…
Abstract The shear creep and creep recovery behavior of narrow molecular weight distribution polystyrene samples of low molecular weight, 1.1 × 10 3 , 3.4 × 10 3 , and 1.57 × 10 4 are reported as a function of temperature, near and above the glass temperature. Time‐temperature equivalence for the total creep complianc…
An n-component substitutional solid solution in a perfect crystal can be characterized uniquely by n−1 independent composition functions. There are n(n−1)/2 distinct short-range-order parameters αij(i,j = 1,2,... n−1) corresponding to these (n−1) independent compositions. The SRO parameters are linearly but not quadra…
This paper reports polarized infrared and raman studies on zircon, zrsio 4 . The 36 k=0 modes of vibration are classified using group theoretical methods. The dielectric parameters epsilon minutes and epsilonseconds have been derived from the reflection spectrum using kramers-kronig theory. Measurements have also been…
The weight loss of Cr 2 O 3 in oxidizing environments (Po 2 = 1 to 10 −3 atm) at 1200°C was measured. Both hot‐pressed and sintered Cr 2 O 3 pellets were investigated in O 2 /Ar gas mixtures, and the dependence of the weight loss on the O 2 partial pressure, the gas flow rate, and the total pressure was determined ind…
A theory of electron scattering by complex atoms is developed in which the target atomic eigenstates and pseudostates are written as linear sums of configurations and the incident electron wave function is expanded in terms of orbitals which satisfy logarithmic boundary conditions on the surface of a sphere. The radiu…
Powder samples of high-density polyethylene and nickel of particle sizes Rp and Rm, respectively, were mixed and compacted at room temperature under a pressure of 1000 kg/cm2. Microscopic examination of polished sections of the compact, by reflected light, showed that the metallic particles did not penetrate the polym…
We assume that (1) the local state of order in the isotropic phase is a symmetric traceless tensor Qαβ, proportional to the anisotropic part of a tensor property such as the magnetic susceptibility; (2) the free energy may be expanded in powers of Qαβ and of its gradients. This allows a unified description covering th…
The spin-wave dispersion relation for the $c$ direction of dysprosium metal in the ferro-magnetic phase at 78\ifmmode^\circ\else\textdegree\fi{}K and in the helical magnetic phase at 98\ifmmode^\circ\else\textdegree\fi{}K has been measured by triple-axis neutron spectrometry. The energy gap measured in the ferromagnet…
According to Munz and Macherauch [1], the dependence of the mobile dislocation density on the strain rate can be estimated from the reduction of stress increments (Δτ/Δ ln \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \varepsilon \limits^. $\end{document}) after a strain rate change. The high strai…
Single crystals of α-MoSe2 have been prepared which are superior to those grown using a chemical transport agent. The dielectric constant of α-MoSe2 has been measured over the range 0.5 to 3.5eV and a value for the direct optical band gap deduced from the observed exciton spectrum; this is compared with the measured a…
A high-temperature mass spectrometric investigation of the vaporization of titanium monosulfide, TiS(s), from 1700–2150°K has shown that the three principal vaporization reactions produce TiS(g), Ti(g) + S(g), andTi(g) + 12S2(g), the second being about four times as important as the first and both more important than…
On the basis of recent optical and EPR work, it has been suggested that the ionized and thermally stable photochromic centers in Ca${\mathrm{F}}_{2}$ consist of one and two electrons bound at an anion vacancy adjacent to a trivalent impurity cation. For the ionized center, we have shown that the energy levels and wave…
Raman spectra of calcite, CaCO3 II, and CaCO3 III have been studied at various pressures as high as 40 kbar. Thirteen lines have been observed in the previously unreported spectrum of CaCO3 II and 20 lines are reported for the CaCO3 III spectrum. These spectra are compared with Raman spectra of aragonite, KNO3 III, an…
Etch-decoration reveals that the rate of removal of carbon atoms exposed at monolayer steps on graphite surfaces is very different from the rate of removal, under identical conditions, at multilayer steps. At 1113 degrees K and a pressure of 1.33 newtons per square meter of oxygen, the rate of oxidation (along the lay…
Nonhindered aromatic α-dicarbonyl molecules show abnormal spectroscopic behavior when compared to other molecules containing carbonyl groups. Taking benzil as a typical example, its photoabsorption and emission spectra cannot be accounted for by the normal Jablonski scheme. The spectral data are consistent with a mech…
The eigenvalues λi of an Hermitian matrix A of order n satisfy the inequality ∑ i = 1n | λi | ≤ n1/2N, where N is the Frobenius norm of A. Let n and ν be, respectively, the numbers of atoms and bonds in the conjugated system of a hydrocarbon, and let E be the corresponding Hückel matrix. Then the Hückel π-electron ene…
Amorphous ice prepared under a wide range of conditions has a density, determined from its buoyancy in liquid oxygen, of 0.94+/-0.02 gram per cubic centimeter, the same as that of ordinary hexagonal ice, with no indication of the glassy superdense ice (2.32 grams per cubic centimeter) reported recently. The diffuse re…
The temperature dependence of the rotational displacement parameters below the second-order phase transitions in SrTi${\mathrm{O}}_{3}$ and LaAl${\mathrm{O}}_{3}$ at ${T}_{a}=105.5 \mathrm{and} 797$\ifmmode^\circ\else\textdegree\fi{}K is described by an exponent $\ensuremath{\beta}=0.33\ifmmode\pm\else\textpm\fi{}0.02…