Materials Literature
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Abstract Die Darstellung einer Reihe von Porphyrin‐Metall‐Komplexen wird beschrieben. Unter Berücksichtigung von bekanntem und neuem Tatsachenmaterial wird eine Deutung der unterschiedlichen Elektronenspektren der Porphyrinkomplexe gegeben. Ausgehend von Salzen ms ‐tetrasubstituierter Porphine, die als Alloporphin‐Der…
We present electron diffraction data from amorphous silicon which cannot be reconciled with the intensity profiles derived from small-crystallite models based on the diamond structure. Our diffraction patterns do reveal a pronounced low-angle scattering which anneals out on progressive heating and is indicative of act…
A new energy parameter ${\mathcal{E}}_{d}$ is introduced to describe dispersion of the electronic dielectric constant. This dispersion energy is found to obey an extraordinarily simple empirical relation in the more than 50 ionic and covalent crystals for which reliable refractive-index dispersion data are available.…
By measuring changes in the dielectric constant of a 1.75:1 cholesteryl chloride–cholesteryl myristate (CM) mixture in the presence of magnetic fields H up to 10 kG, the orientation of the molecular and helical axes with respect to the field direction can be deduced, and the possibility of a dependence of the alignmen…
X-Ray diffraction has shown the existence of a low temperature tetragonal phase of (NH 4 ) 2 TeBr 6 having space group P4/mnc(D 4h 6 ) with a = 7.501, c = 10.765 Å.
A, B , and C bands with peaks at about 4910, 4220, and 3990 Å (mean values for split subbands at 77°K), respectively, were found in the excitation or reflection spectra of visible region of ZnS:Pb (zinc-blende) phosphors. These bands were analyzed by means of Sugano's molecular-orbital theory and identified unambiguou…
A quasiequilibrium treatment of heterogeneous reactions is used to compute the rates of evaporation (desorption) of volatile species formed in the reaction of gaseous O2 with solid tungsten, molybdenum, and graphite under conditions of low pressure and high temperature. The results are compared with existing mass–spec…
Structural phase transitions in perovskite crystals involving displacements of the oxygen octahedra due to the condensation of linear combinations of the triply degenerate ${\ensuremath{\Gamma}}_{25}$ modes at the $R$ corner of the Brillouin zone are discussed with the help of a model Hamiltonian. These distortions ar…
The vaporization of uranium mononitride UN has been investigated by the Knudsen effusion technique in combination with a mass spectrometer. The vaporization occurs incongruently by preferential loss of nitrogen forming the two-phase system nitrogen-saturated liquid uranium–uranium-saturated nonstoichiometric uranium m…
The matrix isolation of silicon monoxide vapor leads to the formation of at least three distinct species: SiO, Si2O2, and Si3O3. Infrared absorptions for these molecules are observed at 1223.9 cm−1 (Si16O); 804.7, 766.3 cm−1 (Si216O2); 972.6, 631.5, 312.0 cm−1 (Si316O3). Equations are given for the in-plane vibrations…
Generalized x-ray scattering factors have been determined from the evaluation of Fourier transforms of atomic-orbital products. Self-consistent-field atomic orbitals for first-row atoms have been studied. Analytical scattering expressions for rapid evaluation on digital computers have been developed. Scattering factor…
We construct a dielectric two-band model which describes and predicts ionization potentials and electronic band structures of binary compounds ${A}_{N}{B}_{8\ensuremath{-}N}$. Only the density and dielectrically defined electronegativity difference are required as input data. The method is applied to 19 tetrahedrally…
Electrical conductivity, differential thermal analysis, ac Hall effect, and x-ray diffraction measurements were used to investigate the low-temperature behavior of flux-grown single crystals of the titanium oxides. Monoclinic ${\mathrm{Ti}}_{3}$${\mathrm{O}}_{5}$ and the triclinic Magn\'eli phases ${\mathrm{Ti}}_{4}$$…
The magnetic electron distribution in Mn${\mathrm{Pt}}_{3}$ ferromagnetic alloy has been determined by the polarized neutron technique. The Mn form factor in the ferromagnetic state has been determined and agrees closely with the theoretical one calculated for the free atom. The magnetic moments are $(3.64\ifmmode\pm\…
The contributions of internal strain and charge redistribution to the piezoelectric constants of tetrahedrally coordinated ${A}^{N}{B}^{8\ensuremath{-}N}$ crystals are discussed. It is shown that the reversal of sign of the piezoelectric constant on going from $N=1 \mathrm{and} 2$ to $N=3$ can be explained quantitativ…
The temperature dependence of the longitudinal and the shear sound-wave velocity along the [100] axis in ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ is presented. The longitudinal velocity exhibits an anomaly at 130\ifmmode^\circ\else\textdegree\fi{}K, where there is an easy-axis change from the [111] to the [100]. Both she…
The Jahn-Teller coupling of a triplet state in cubic surroundings to both ${E}_{g}$ and ${T}_{2g}$ modes of vibration can lead to a vibronic ground state that includes both tetragonal and trigonal distortions if the energy difference between the static distortions is small. A simple model is set up to study the proper…
This paper reports optical and magnetic properties of tetramethyl ammonium manganese trichloride, [${(\mathrm{C}{\mathrm{H}}_{3})}_{4}$N][Mn${\mathrm{Cl}}_{3}$]. Magnetically, the system is one of very weakly interacting chains of ${\mathrm{Mn}}^{++}$ ions. Magnetic-susceptibility measurements are given from room temp…
The ferrimagnetic spinels ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, Ni${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$, Co${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$, Mn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$, and Mg${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$ have been prepared and studied with the M\"ossbauer-effect technique over a wide temper…
Within a two-state formalism, a systematic procedure is developed for deriving the difference between the gerade and ungerade state potentials from resonant charge-exchange total cross sections. It is shown that three potential constants may be derived from (i) the relative monotonic velocity dependence of the cross s…