Materials Literature
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First- and second-order Raman scattering from graphite has been studied. The second-order spectra of single crystals and of highly oriented pyrolytic graphite are continuous and exhibit several well-defined bands which can be attributed to features in the density of vibrational states as determined from current lattic…
Semiempirical molecular orbital calculations have been carried out on some of the common substitutional species in diamond-nitrogen, boron, silicon, oxygen, and the nitrogen pair. The results show that this model reproduces many of the electronic and vibrational properties of these defects extremely well. In particula…
Two semiempirical crystal orbital schemes are outlined for the calculation of the properties of perfect and defective solids. Both use periodic boundary conditions with a large unit cell (LUC) to map special points of the Brillouin zone onto the point k=0. One method involves the complete neglect of differential overl…
The results of a neutron diffraction study on the short-range order in the TeO 2 -Li 2 O glassy system are presented. On the basis of the obtained atomic radial distribution function a model for structural recombination in TeO 4 tetrahedra for tellurite glasses is proposed. This model takes into account the influence…
(Second of Two Parts)How Do Defects in Biosynthesis Explain Genetic Diseases of Collagen?There are many rare genetic diseases that involve connective tissues, such as skin and bone.As the information reviewed above about collagen structure and biosynthesis accumulated, biochemical data were quickly obtained to explain…
Rates of plagioclase crystal growth at constant temperature have been measured for a series of compositions in the system CaAl 2 Si 2 O 8 (An)—NaAlSi 3 O 8 (Ab). A microscope heating stage was used at temperatures near the liquidus to observe and photograph the growing crystals, and a resistance furnace quenching tech…
We present a theory to explain the anomalous enhancement of light scattering from molecules adsorbed at a metal-solution interface. It is found that tunneling of electrons between a surface molecule and the metal induces a resonance at a point in the vicinity of the Fermi surface. A dynamical equilibrium due to photoi…
A background continuum in the Raman spectrum of adsorbed molecules at a silverelectrolyte interface is observed experimentally. This background continuum is potential dependent on the Stokes and anti-Strokes of the spectrum and fits a Fermi distribution function on the anti-Stokes side of the spectrum. The continuum i…
A wall-induced birefringence in a nematic liquid crystal above the nematic-isotropic phase transition point has been observed for the first time. It is expected that this phenomenon will provide a useful tool to study the nature of aligning forces at liquid-crystal-solid interfaces.
The lowering of the Fermi energy in stage-1 Fe${\mathrm{Cl}}_{3}$-intercalated graphite is directly measured in the spectrum of electronic excitations from carbon $1s$ core states to empty carbon $2p$ states which appear after intercalation. The shape of the core exciton spectrum is related to the initial distribution…
New structural models for 2\ifmmode\times\else\texttimes\fi{}1 and 4\ifmmode\times\else\texttimes\fi{}2 reconstructed (100) surfaces of Si determined from energy-minimization claculations are presented. The optimal 2\ifmmode\times\else\texttimes\fi{}1 and 4\ifmmode\times\else\texttimes\fi{}2 structures are found to co…
The catalytic activity of MnO/sub 2/ prepared by different methods has been determined from the initial rate of decomposition of H/sub 2/O/sub 2/ and the conversion of CO to CO/sub 2/. The activity is correlated with various physicochemical properties such as active oxygen, surface excess oxygen, surface OH groups, cr…
Abstract With the purpose of obtaining information needed for hazard prevention, pure liquid dialkyl peroxides (di-t-butyl peroxide (1), bis(1-methyl-1-phenylethyl) peroxide (2), t-butyl 1-methyl-1-phenylethyl peroxide (3), 2,5-bis(t-butyldioxy)-2,5-dimethylhexane (4)) were subjected to thermal-decomposition experimen…
Dislocation damping as a function of strain amplitude following quenching and during 1-MeV electron irradiation was investigated by measuring Young’s modulus and the logarithmic decrement in high-purity polycrystalline copper. A ’’peaking effect,’’ an initial increase and subsequent decrease in the damping, was observ…
A method is presented for localizing molecular orbitals, based on diagonalizing subunits of the density matrix. First, nonbonding orbitals are found by diagonalizing the monatomic subunits; then, diatomic sigma or pi bonding and antibonding orbitals are obtained from the diatomic subunits for all bonded pairs of atoms…
The radical anions of methyl-, methoxy-, fluoro-, cyclopropyl-, and cyanocyclooctatetraene were generated by electrolytic reduction of the neutral compounds in liquid ammonia.The electron spin resonance spectrum of each radical anion is assigned, and a clean even-odd alternation of the spin densities is observed in ea…
Abstract Na 2 S 2 CO 3 crystallizes in 4 modifications. The familiar monoclinic a-form stable at ambient temperature transforms into the trigonal β-form at 330 °C which at 388 °C converts to b ccy-Na 2 S 2 O 3 . These transformations are reversible. Unstable orthorhombic α'-Na 2 S 2 CO 3 (Pna2 1 ) is obtained by dehyd…
Abstract A magnesian halotrichite [(Fe 0.63 Mg 0.37 ).Al 2 (SO 4 ) 4 .22H 2 O] from a fumarole deposit on the active andesitic volcano of White Island, New Zealand, occurs as the major component in the mixture halotrichite—H 2 S0 4 ‐H 2 0—alunogen, with accessory gypsum, alunite, anhydrite, quartz, cristo‐balite, and…
Abstract Two new intermetallic compounds K 3 Ag 3 As 2 and K 3 Cu 3 As 2 have been prepared and their crystal structures determined. They crystallize in the rhombohedral space group R3̅m with K 3 Cu 3 As 2 : a = 576(2) pm, c = 2026(5) pm, K 3 Ag 3 As 2 : a = 599(2) pm, c = 2135(4) pm. and are isotypic to K 3 Cu 3 P 2
Abstract A procedure is described which permits the classification of solvents according to their effect on polycarbonate (PC): Class I—dissolve amorphous or crystalline PC Class II—dissolve only amorphous PC Class III—convert amorphous PC to crystalline PC Class IV—none of the above. This classification is achieved b…