Materials Literature
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Moderately strong, very broad absorption bands observed in dilute lanthanide bromide solutions in nearly anhydrous ethanol are interpreted as electron transfer from the highest filled M.O. to the partly filled 4f shell in the case of Nd(III), Sm(III), Eu(III), Tm(III) and Yb(III). Good agreement is obtained with a the…
Abstract The dynamic shear modulus at very high strains, ( G ∞ ), of carbon black filler loaded vulcanizates is regarded as due to the product of two factors: ( a ) a hydrodynamic interaction due to filler particles, and ( b ) a second factor for which evidence is given suggesting that it arises from a few strong link…
On the basis of 190 runs made up to 1860°C in sealed noble‐metal containers the following revisions have been made in the equilibrium diagram for the system A1 2 O 3 –SiO 2 . Mullite melts congruently at 1850°C. The extent of equilibrium solid solution in mullite at solidus temperature is from approximately 60 mole %…
A set of best values for t he te mperatures a nd enthalpies of fusion alld transition for the n-paraffins is presented. From a n a nalysis of these data a general qualitative t heory of the phase behavior of the n-paraffins is developed. Four di stinct. crystal structures-h exagonal, t riclinic, monoclinic, and orthor…
Trap depths and densities can be determined from the analysis of the dependence of space-charge-limited currents on applied electric field in insulators. Values obtained from space-charge-limited current measurements are compared with those obtained from thermally stimulated currents and from photocurrent decay on the…
In Hartree-Fock theory and its various generalizations, it is customary to solve an eigenvalue problem involving an effective one-body Hamiltonian. The eigenvectors determine the Fock-Dirac density matrix, which also appears in the effective Hamiltonian, and solution proceeds iteratively until self-consistency is achi…
Compositions in the system KNbO 3 ‐NaNbO 2 have been hot‐pressed to yield ceramics with relative densities greater than 99%. Because these materials lack any degree of pyroplastic behavior, temperatures approaching those required for air sintering are needed. These hot‐pressed specimens exhibit a finer microstructure…
Abstract Electron microscope observations on some polycrystalline metals suggest that after small to moderate deformation, recrystallization occurs by the migration of the original grain boundaries. A theory based on this mechanism can account for the known form of the recrystallization kinetics without necessarily in…
P-type semiconducting diamonds can be formed at high pressures and temperatures out of mixtures of graphite and catalyst metal (Ni, Fe, etc.) to which small amounts of B, Be, or Al have been added. The crystals may have resistivities of as low as 103 ohm-cm with activation energies for conduction ranging between 0.1 a…
IT IS WELL KNOWN THAT THE ENERGY, DIPOLE MOMENT, AND MANY OTHER PROPERTIES OF AN ATOM OR MOLECULE CAN BE CALCULATED IF THE PAIR DENSITY MATRIX, A FUNCTION OF 12 VARIABLES, IS AVAILABLE. For a system with N electrons and therefore 3N degrees of freedom, this is a great simplification, at least in principle if not yet i…
An investigation of the magnetic structure and properties of Mn${\mathrm{Cr}}_{2}$${\mathrm{O}}_{4}$ has been carried out by means of neutron diffraction and an evaluation of the suitability of various proposed theoretical models has been made. From room-temperature diffraction patterns it is established that Mn${\mat…
Semiconducting crystals of cubic BN may be prepared at high pressures and temperatures by adding small amounts of selected impurities to the synthesis mixture (hexagonal boron nitride plus lithium or magnesium nitride). P-type crystals, blue in color, can be prepared by adding Be; they may have resistivities of about…
Using a simple one-dimensional model of H bonds, vibrational-energy eigenvalues, eigenfunctions, transition moments, and absorption intensities are calculated for a series of symmetric and asymmetric double-minimum (D.M.) potentials. On the basis of the results obtained, the necessary requirements for observing double…
The thermal conductivity from 3\ifmmode^\circ\else\textdegree\fi{} to 300\ifmmode^\circ\else\textdegree\fi{}K of single crystals of the two spinels, diamagnetic Mg${\mathrm{Al}}_{2}$${\mathrm{O}}_{4}$ and paramagnetic ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, has been measured and analyzed. The heat is transported by pho…
The polarized absorption spectra of Ni2+ and Co2+ in crystals of ZnO, ZnS, and CdS; Ni2+ in crystals of Cs2ZnCl4 and Cs2ZnBr4; and Cu2+ in ZnO have been measured at 4°K, 77°K, and room temperature. The spectra have been interpreted by the use of crystal field theory for the states of the (3d)n configuration acted on b…
The quantum theory of the frequency- and wave-number-dependent dielectric constant in solids is extended in order to study the full dielectric constant tensor and to include local-field effects. Within the framework of the band theory, an explicit expression for the dielectric constant tensor, neglecting local-field e…
Abstract After a brief introduction discussing the basis of molecular-field theories, we introduce a generalization of Anderson’s treatment of antiferromagnetism which enables us to take higher-order exchange interactions into account as well as anisotropy terms. We restrict ourselves to terms quadratic in the spins.…
Abstract X-ray analyses of selected samples from the argillaceous subdivisions of the English Wealden indicate that illite, kaolinite, and mixed-layer structures are present in variable amounts. The clay mineral assemblage is thought to reflect parent material, weathering conditions in the source area, and possibly so…
Browsing in books, review articles and conference reports, one sometimes nowadays comes across pictures like fig. 1. This peculiar object, which might be mistaken for a piece of modern sculpture, is labelled “The Fermi surface of magnesium”. What does it mean, to say that magnesium has a Fermi surface, and how is it d…
Abstract The principle of the new gas‐phase method of polycondensation consists of carrying out the polycondensation reaction of two high reactive compounds at a liquid—gas interface. The gas‐phase method permits the synthesis of polyamides with rapidly hydrolyzing diacid chlorides (e.g., oxalyl chloride), which canno…