Structure cristalline de K2V3O8 ou K2(VO)[V2O7]
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Electronic band structure of the alkali halides. II. Critical survey of theoretical calculations
A review of the results of published energy-band calculations for the alkali halides is presented in which the experimental results of the preceding paper are used as a basis for critical comparison of theory and observation. Band calculations employing Slater exchange are shown to be inadequate, while calculations wh…
Unified model of the insulator-metal transition inTi2O3and the high-temperature transitions inV2O3
A unified band-crossing model of the insulator-metal transition in ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ and the high-temperature tranistion in ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ is presented. The model is based on a Hartree-Fock free-energy calculation including electron-electron Coulomb energy, elastic energy, and…
Crystal Structure of the Glaserite Form of BaNaPO4
Crystals of BaNaPO 4 were grown from a Ba 3 P 2 O 8 –Na 2 B 4 O 7 melt. The crystals are trigonal, space group [Formula: see text]with a = 5.622(4) and c = 7.259(5) Å. The structure, isotypic with that of glaserite, was refined by full-matrix least-squares methods to a final R value of 0.042 using 218 unique reflectio…
Energy transfer betweenEr3+ions in LaF3
The decay of the excited $^{4}S_{\frac{3}{2}}$ state of ${\mathrm{Er}}^{3+}$ ions in La${\mathrm{F}}_{3}$ at 295\ifmmode^\circ\else\textdegree\fi{}K has been investigated in detail. The energy is transferred from the thermally populated multiplet $^{2}H_{\frac{11}{2}}$. The decay curve of the luminescence from $^{4}S_…
An X-Ray Line Broadening Analysis in the Vacuum-Evaporated Silver Films
An X-ray integral breadth analysis has been made for the 111, 200, 220, 311 and 222 diffraction profiles recorded on a Geiger counter X-ray diffractometer from the vacuum-evaporated thin films of silver in the range of thickness 580 to 2125 Å. The analysis based on the methods of single and multiple order of reflectio…
Crystal Structure of Antiferromagnetic NiO Determined by X-Ray Topography
Spontaneous magnetostriction of NiO, which consists of two strain components, is reexamined in detail by Berg-Barrett method. The strain components thus determined are e x ' x ' -e y ' y ' =-5.4×10 -4 and e z ' x ' =0.91×10 -4 , respectively. These values are a few times as large as those found previously by Yamada et…
A comparison of generalized cumulant and projection operator methods in spin-relaxation theory
The general spin-relaxation theories of Albers and Deutch and of Argyres and Kelley based on different projection operator methods, and the theory of Freed based on generalized cumulant expansions are compared. It is shown that the first two yield equivalent expressions for the time evolution of the spin density matri…
Distribution of charge in electrets
Measurements are reported of the total charge and its mean position in liquid-charged FEP electrets. A new nondestructive technique has been used. The large difference in decay rates of positive and negative liquid-charged electrets is accompanied by quite different behavior of the deposited charge as it migrates thro…
Interface excitations in metal-insulator-semiconductor structures
The interface excitations associated with the inversion layer of a metal-insulator-semiconductor structure are investigated. These excitations can be regarded as coupled modes whose components are the two-dimensional-electron-gas plasmon and the surface plasmon of the metal-insulator interface. The dependence of the c…
Onsager mechanism of photogeneration in amorphous selenium
The Onsager theory of dissociation has been used to explain the electric field, excitation wavelength, and temperature dependence of photogeneration in amorphous selenium. The Onsager theory was formulated to explain the departure from Ohmic behavior in either weak electrolytes or solid dielectrics, and the analysis o…
The structure of the clean Mo[001] surface
An analysis of low-energy-electron-diffraction data from a clean Mo{001} surface was carried out, which has determined the atomic structure of this surface and provided the parameters of a scattering model needed to analyze ordered overlayers. The analysis was based upon the comparison between the intensity spectra ca…
Further studies on the genusBerkeleyaGrev.
Detailed light and electron microscopical studies on the diatom genus Berkeleya Grev. clarify relationships between the four species and support the separtion of B. fragilis and B. micans as two distinct taxa.
ChemInform Abstract: THE CRYSTAL STRUCTURE OF MAGNESIUM TETRAMETAPHOSPHATE, MG2P4O12
Abstract Die Kristallstruktur von (I) wird durch direkte Methoden bestimmt und anhand von 3‐dimensionalen Röntgenbeugungsdaten verfeinert.
Raman study of polar phonons in lithium sulphate monohydrate
A detailed Raman study of phonons in monoclinic Li 2 SO 4 H 2 O and its deuterate is given. The spectrum for two directions of the phonon wave vector at 45 degrees to the y axis from liquid nitrogen to room temperature have been determined and the majority of the lines observed have been identified: although the conve…
Optical anisotropy in GaSe
Normal-incidence reflectivity spectra of layer-type beta -GaSe crystals have been measured for E perpendicular to c as well as E//c at 78K. A strong anisotropy in the selection rules for interband transitions has been observed and a suitable energy level scheme is proposed. The reflectivity spectra of the mixed polyty…
The low-temperature thermal conductivity of polyethylene
Measurements are presented of the temperature variation between 2K and 100K of the thermal conductivity, kappa of several samples of extruded polyethylene. At high temperatures ( approximately 100K) there is an anisotropy in kappa , with the values measured parallel to the extrusion direction up to 5 times greater tha…
Optical theorems for three-to-three processes
Optical theorems for three-to-three processes are derived from S-matrix principles. These theorems express all single, double, and multiple discontinuities across all combinations of normal threshold cuts in terms of physical scattering amplitudes. The 216 functions corresponding to all combinations of sides of the 16…
Effects of diffusion on gaseous cavitation bubbles
Rectified diffusion is a mechanism whereby a gas bubble, set into pulsation by a sound field, grows in size because of an effective gating action by the bubble surface area. Bubbles that might otherwise dissolve will grow instead if the sound pressure amplitude exceeds a threshold that depends on the bubble size. A th…
Determination of the crystal symmetry of the polymorphs of thallium indium disulfide, TlInS2
Several modifications of TlInS 2 crystallize from melts of this composition with annealing at various temperature. Symmetries and lattice parameters determined by the x-ray precession method are as follows: I. ( = β ), monoclinic, a ∼ b = 7.76 ± 0.01 Å, c = 30.01 ± 0.02 Å, β = 90°10′ ± 5′, P 2 1 / m , Z = 16, D x = 5.…