bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemical Properties of SH− Ions in KCl and KBr Crystals
Authors: Facey O. E. , Jacobs P. W. M. 
Published: July 2007

AbstractThe photochemistry of KCl and KBr containing SH− impurity ions has been investigated. In addition to the formation of S− and U2‐centres reported previously, U‐centres are formed in high yield and F‐centres in low yield. The thermal contribution to the photochemical process is slight (≈︁ 0.013 eV). The kinetics of the decay of U2‐centres has been shown to be bimolecular and to correspond mainly to the reaction S− + Hi → SH−, where Hi denotes an interstitial hydrogen atom. A model involving the utilization of the thermal energy released during a radiationless transition from the excited state is successfully used to give a qualitative explanation of the data.
Clustering of Defects in Neutron‐Irradiated Beryllium Oxide
Authors: Rau R. C. , Chase G. A. 
Published: July 2007

AbstractTransmission electron microscopy and X‐ray diffraction have been combined to study clustering of defects in BeO irradiated to neutron dosages ranging from 0.5 to 11.7×1020 nvt at pile ambient temperature (≈︁ 100°C). Dot clusters which form in the microstructure at dosages greater than about 1.0×1020 nvt are interpreted as being small interstitial loops, oriented on basal planes. X‐ray diffraction patterns contain duplex peaks consisting of sharp components, which reflect changes in the bulk lattice, and broad components which are related to the basal clusters. The observations are consistent with a model containing interstitial basal clusters and random point interstitials, but do not necessarily rule out the presence of point vacancies.
On the Superstructures of Ta2O5 and Nb2O5
Authors: Spyridelis J. , Delavignette P. , Amelinckx S. 
Published: July 2007

AbstractThe superstructures of tantalum and niobium pentoxide are studied. The observations made support the assumption that these, and related crystals, have a “shear structure” and that this shear structure can be observed directly. It is shown that the size of the unit cell depends on the exact stoichiometry of the compound. A model is proposed which explains both the details of the diffraction pattern and the geometry of the line system.
The Lattice Vibrations of Nickel in Krebs's Model
Authors: Shukla M. M. , Dayal B. 
Published: July 2007

AbstractThe vibration spectrum of nickel is studied using Krebs's model. The phonon dispersion curves for the three symmetry directions [100], [110], and [111] are presented and are found to be in very good agreement with neutron scattering measurements. Good agreement is also obtained with the curve of θ against T. The computed G(v) curve is compared with the experimental curves and some agreement is found.
Lattice Dynamics of Solid Adamantane
Authors: Stockmeyer R. , Stiller H. H. 
Published: July 2007

AbstractThe frequency distributions of the translational and rotational motions of H‐atoms in C10H16 and their corresponding amplitudes are determined by means of neutron time‐of‐flight spectroscopy for several temperatures. An estimate of the frequency distribution for the low temperature phase with the statement of James and Keenan (octopole‐octopole interactions) leads to an agreement with the experimental results.
Spin‐Orbit Splitting of the Valence Band of Wurtzite Type Crystals
Authors: Gutsche E. , Jahne E. 
Published: July 2007

AbstractA 12×12 representation is given of the valence band Hamiltonian at k = 0 which includes the spin‐orbit interaction. Expressions are derived for the energies and the linear combinations of the wave functions for the Γ7, Γ8, and Γ9 subbands. The whole valence band is completely determined by eight parameters: three energies, two parameters coupling states of equal spin, and three parameters coupling states of opposite spin. In principle, all parameters can be obtained experimentally from the energy separations and oscillator strengths for interband transitions for polarization ⟂ c and ∥ c. Anisotropic spin‐orbit interaction and mixing of states originating from the two anions per unit cell are discussed.
Absorption and Dispersion of Light by Molecular Excitons
Authors: Davydov A. S. , Myasnikov E. N. 
Published: July 2007

AbstractA calculation is made of the real and imaginary parts of the dielectric permeability of molecular crystals due to exciton states, using retarded Green's functions. The interaction of excitons with acoustic and optical phonons is taken into account at different temperatures of the crystal. The dependence of the optical refractive index and the damping coefficient on the frequency of the incident light is obtained in the region of the exciton bands.
Electrical and Photovoltaic Properties of PbSSi Heterodiodes
Authors: Sigmund H. , Berchtold K. 
Published: July 2007

AbstractThe electrical and photo‐electrical properties of PbS‐Si heterodiodes are investigated. The PbS films are grown on Si by a water‐solution reaction at room temperature. The forward and reverse characteristic is similar to that for other heterojunctions (recombination‐tunneling mechanism). The spectral response is in the wavelength range 1 to 3 μm at room temperature. The sensibility in the PbS peak is about 6 × 103 V/W.
Calculation of the Specific Surface Energies of Crystal Planes by Investigating the Orientation of Crystal Nuclei on Inert Substrates
Authors: Pangarov N. A. 
Published: July 2007

AbstractOn the basis of the Stranski‐Kaischew method of the average works of separation, a method is presented for calculating the specific surface energies of crystal planes by investigating the axes of prefered orientation during crystallization on inert substrates. This method is applicable both to crystallization from the gaseous phase and to metal electro‐deposition. The method is applied to the electro‐deposition of silver, and the values of the specific surface energies for the (111), (100), and (110) planes are calculated.
Mikromagnetische Behandlung der Wechselwirkung zwischen Versetzungen und ebenen Blochwänden. I. Allgemeine Theorie
Authors: Pfeffer K.‐H. 
Published: July 2007

AbstractInfolge der inneren Spannungen, die von den Versetzungen hervorgerufen werden, wird der Magnetisierungsverlauf innerhalb und außerhalb einer Blochwand modifiziert. Für das Gesamtsystem Versetzung‐Blochwand werden durch Minimalisierung der Gesamtenergie die mikromagnetischen Gleichungen in linearisierter Form abgeleitet, wobei die magneto‐elastische Kopplung in Voigtscher Näherung behandelt wird. Die linearen Differentialgleichungen besitzen im Unterschied zu den Gleichungen, die in der Theorie der Einmündung in die ferromagnetische Sättigung auftreten. Koeffizienten, die von dem Magnetisierungsverlauf der ungestörten Blochwand abhängig sind. Zur Lösung derselben wird das Differentialgleichungssystem entsprechend dem nicht‐lokalen Charakter des magnetischen Streufeldes in ein System von zwei linearen, inhomogenen Integralgleichungen übergeführt. In der zugrunde gelegten linearen Näherung ergibt sich die Energieänderung, die mit der Änderung der Magnetiaierungsverteilung verknüpft ist, als die Hälfte der hiermit verbundenen Änderung der magnetoelastischen Kopplungsenergie. Aus der Struktur der magnetoelastischen Kopplungsenergie werden qualitative Aussagen über die Magnetisierungsverteilung und das hieraus resultierende Wechselwirkungspotential im System Blochwand–Versetzung abgeleitet.
Effets de la desaimantation thermique sur les cycles d'hystérésis
Authors: van Dang N. 
Published: July 2007

AbstractUn échantillon ferromagnétique désaimanté thermiquement pouis soumis à des cycles d'hystérésis symétriques d'amplitude ±HA présente un curieux effet de bascule tres différent des phénomènes de reptation et de bascule positive ou négative déjà connus par de nombreux chercheurs travaillant sur l'hystérésis. On a étudié systématiquement ce phénomène et comparé les données expérimentales avec le schéma de Néel‐Preisach.
Some Relations for Straight Dislocations
Authors: de Wit R. 
Published: July 2007

AbstractExpressions are presented for the stress, strain, dilatation, and displacement due to an infinitely long straight dislocation, as well as the force per unit length and the total force on a straight dislocation due to another infinite straight dislocation. They differ from previous expressions in the literature in that they are given completely in tensor or vector notation. They are limited to the case of a linear, isotropic, infinite continuum.
Optical and Photoconductive Phenomena in Cuprous Oxide
Authors: Spyridelis J. , Stoimenos J. , Economou N. 
Published: July 2007

AbstractThe optical absorption of cuprous oxide is affected by the defect structure and this is most pronounced in the middle of the stability range, indicating that the observed absorption bands are due to aggregates of vacancies. A simultaneous measurement of the photoconductivity leads to a direct relationship between the exciton stimulated photoresponse and the defect structure.
The Model Potential for Systems with Closed Shells
Authors: Abarenkov I. V. , Antonova I. M. 
Published: July 2007

AbstractThe pseudo‐potential is set up for the Cauchy problem of the Hartree‐Fock equation for an extra electron outside of an atomic system with closed shells. As an approximation to this potential a “model” potential is set up and the method of its determination is developed. The results of calculations for Na+ and Cl− ions are given. The quality of the approximation of the model potential is discussed. The model potential can be applied to the calculation of the valence electron in ionic crystals.
Noncentral Force Model for Hexagonal Close‐Packed Crystal Lattices
Authors: Metzbower E. A. 
Published: July 2007

AbstractA Born‐von Karman model of the hexagonal close‐packed lattice was considered using a combination of central and angular forces between various sets of neighbors. The interactions between nearest neighbors in the plane were regarded as central forces while the interactions between nearest neighbors out of the plane and next nearest neighbors out of the plane were considered to be noncentral, i.e. both central and angular. Three materials with different axial (c/a) ratios were considered: beryllium (1.568), magnesium (1.624), and zinc (1.855). The equations of motions were evolved and the force constants were related to the elastic constants of the material. The eigenvalues of the secular equation were solved for one hundred twenty one (121) points in that portion of the Brillouin zone irreducible under symmetry operations. The frequency spectrum for each material was obtained from these eigenvalues. The temperature dependence of the specific heat of each material was calculated using the appropriate frequency distribution function. The Debye characteristic temperature and the Einstein characteristic temperature were also obtained as a function of temperature.
The Orientation and Shape of θ Precipitates Formed in an AlCu Alloy
Authors: Vaughan D. , Silcock J. M. 
Published: July 2007

AbstractSeveral new orientation groups have been observed for θ precipitates in an Al‐4% Cu alloy. All orientations so far known for θ in relation to both θ′ and the aluminium matrix are summarised. There are 159 known possible orientations for a θ particle relative to the aluminium matrix. Details of the matching interfaces and some of the factors governing nucleation and growth of θ particles are discussed.
X‐Ray Diffraction and Magnetic Studies of Solid Solutions Bi1−xCaxMnO3
Authors: Bokov V. A. , Grigoryan N. A. , Bryzhina M. F. 
Published: July 2007

AbstractSolid solutions with the general formula Bi1–xCaxMnO3 (0.2 ≦ x ≦ 1) are found to possess the perovskite structure. The phase diagram based on X‐ray diffraction studies involving cubic, orthorhombic and monoclinic modifications is constructed. It is concluded from conductivity and X‐ray data that the transition into the monoclinic II modification is connected with some type of electron ordering on manganese ions. The changes in the paramagnetic Curie temperature resulting from these structural transitions are discussed. The magnetic ordering occurring in the system at about 110 °K can be explained if Zener's double exchange interaction Mn3+‐O2−‐Mn4+ is assumed to occur only in modifications in which electron ordering does not exist. The antiferromagnetic exchange interaction Mn4+‐O2−‐Mn4+ and the weak exchange interaction Mn3+‐O2−‐Mn3+ (the latter being ferromagnetic at a > 3.8 Å or antiferromagnetic at a < 3.8 Å) are proved to be responsible for ferromagnetism in the range 0.2 ≦ x < 0.4, antiferromagnetism in the range 0.4 ≦ x ≦ 0.8 and weak ferromagnetism in the range 0.8 < x ≦ 1.
Exciton Absorption in Doped Germanium
Authors: Asnin V. M. , Rogachev A. A. 
Published: July 2007

AbstractA study is made of the variation in the shape of the direct absorption edge in germanium with doping level. Increasing the impurity density leads to a broadening and disappearance (at a concentration of about 1016 cm−3) of the direct exciton maximum as well as affecting the shape of the absorption spectrum near the edge.
Valence Band Structure of Wurtzite Type Crystals
Authors: Jahne E. , Gutsche E. 
Published: July 2007

AbstractThe valence band structure of wurtzite type materials is investigated using a k · p approximation. The E(k) dependence for the bands A, B, and C is completely determined by six parameters: two for k ∥ c, three for k⟂c and one additional parameter for a general direction. Relationships between the effective masses at k = 0 are given for the three bands. Even near k = 0 the sub‐bands are strongly non‐parabolic. The constant‐energy surfaces retain their rotational symmetry. Numerically calculated E(k) curves are presented for k ∥ c and k ⟂ c for CdS and CdSe.
Magnetic Field Dependence of Current Oscillations in Piezoelectric Semiconductors
Authors: Hervouet C. 
Published: July 2007

AbstractCurrent oscillations are observed in various piezoelectric semiconductors when an electric field, applied in a piezoelectrically active direction, exceeds a certain critical value. The threshold field and the current minimum are decreased by a transverse magnetic field which increases the piezoelectric amplification. This phenomenon is studied theoretically using Spector's model for all values of the magnetic field. There is good agreement between theory and experiment for materials with a low value of σ τ (σ is the conductivity and τ the relaxation time of carriers) but only qualitative agreement for materials with a high value of σ τ because of the classical limit of the theory.
Optical Observation of Domain Motion in Ferroelectric BaTiO3
Authors: Kobayashi J. 
Published: July 2007

AbstractMicroscopic observations are made of a BaTiO3 crystal cut in parallel to the ferroelectric axis. Besides nucleating and forward growth of antiparallel domains, sidewards motion of the expanding domains is clearly observed. The fine structure of a nucleating domain is found to consist of a pair of bright stripes in the microscopic view at the point of extinction. The visibility of the antiparallel domains is explained.
A Note on the Consistency of Values of the Spontaneous or Saturation Magnetization of Polycrystalline Iron and Nickel at 298 °K
Authors: Arajs S. , Dunmyre G. R. 
Published: July 2007

AbstractMass magnetization of polycrystalline iron and nickel, σ(Hi, 298 °K), where Hi is the internal magnetic field, has been studied by means of a vibrating sample magnetometer at 298 °K using spherical samples. An absolute technique, based on the soft magnetic nature of iron, has been used to calibrate the magnetometer. The spontaneous magnetization, determined by the [σ(Hi, 298 °K)]2 vs. σ(Hi, 298 °K)/Hi technique, is found to be (217.1 ± 0.2) G cm3 g−1 for iron and (55.07 ± 0.11) G cm3 g−1 for nickel. The ratio of these two quantities is in excellent agreement with the corresponding ratio of the saturation magnetizations at 288 °K determined by Danan [2] but not with that reported by Weiss and Forrer [1].
Nuclear Quadrupole Interaction of 23Na and 11B and the Crystal Structure of NaBF4
Authors: Weiss Al. , Zohner K. 
Published: July 2007

AbstractThe nuclear quadrupole interaction of 23Na and 11B in NaBF4 is investigated between 23 and 260 °C using single crystals and crystalline powder respectively. At 23 °C the following results are found: e2 q Q/h (23Na) = 1008.4kHz; e2 q Q/h (11B) = 59.9 kHz; η (Na) = 0.095; η (B) = 0.65. The crystal structure is as follows: Space group Cmcm; a = 6.841 Å, b = 6.266 Å, c = 6.799 Å; Z = 4; Na and B in (4c) with y (Na) = 0.656; y (B) = 0.161; F(I) in (8 f) with y = 0.290; z = 0.086; F(II) in (8 g) with x = 0.163; y = 0.032. The point charge model, NMR‐investigation and the crystal structure agree well assuming a 55% ionic character for the B‐F bond. The high temperature phase of NaBF4 (between 250 and 260 °C) has non‐cubic point symmetry of the B: e2 q Q/h (11B) = 34 kHz.
Einfluß der Nahordnung um Magnesiumverunreinigungen in Wismutschmelzen auf die Kernresonanzfluoreszenz‐Ausbeute
Authors: Holtmeyer G. , Kalus J. 
Published: July 2007

AbstractEs wurden Kernresonanzfluoreszenz‐(KRF‐)Untersuchungen als Streuexperiment an Mg24 durchgeführt, das als Verunreinigung in Bi eingebaut war. Bei Anhebung der Quellen‐temperatur von Raumtemperatur bis knapp über den Bi‐Schmelzpunkt (300 °C) änderte sich die KRF‐Ausbeute nicht, bei hohen Temperaturen (800 °C) trat eine starke Zunahme um 50% ein. Es wird ein Hartkugelmodell für Schmelzen entwickelt, das diese Zunahme durch Veränderung der Bi‐Nahordnung um die Mg‐Kerne zu deuten versucht.
Threshold Energy for Atomic Displacement in Cadmium Telluride
Authors: Bryant F. J. , Webster E. 
Published: July 2007

AbstractA study of the luminescence emission spectrum of cadmium telluride at 77 °K before and after bombardment with monoenergetic electrons in the energy range 100 to 400 keV has been made. Enhancement of the luminescence emission band at 1.13 μm after radiation damage of p‐type cadmium telluride permits the measurement of an energy threshold at 340 keV. This is an energy threshold for the production of primary damage in the crystal. An electron of 340 keV energy could transfer a maximum of 7.8 eV to a tellurium atom or 8.9 eV to a cadmium atom. The damage causing the enhancement of the 1.13 μm luminescence emission band is found to anneal completely in a single stage between 110 and 140 °K. The damage causing a decrease in the 0.89 μm luminescence emission band anneals partially (40%) in the same temperature range (110 to 140 °K). The remainder of the damage causing a decrease in the 0.89 μm luminescence emission band anneals in a continuous manner between 140 °K and room temperature.
Study of Electron Lifetime in p‐Si
Authors: Abdullaev G. B. , Iskender‐Zade Z. A. , Dzhafarova E. A. , Chelnokov V. E. 
Published: July 2007

AbstractThe lifetime τn of minority carriers in p‐Si is studied over a wide range of temperatures (17 to 245 °C) and injection levels (0.05 to 6). It is found that at a temperature of T ≈ 160 °C and within the injection level range Δ = 0.05 to 2.5, τb ≈ 35 μs; below this temperature, τn increases from 1 to 20 μm, and above it, decreases from 160 to 55 μs with increasing directly flowing current through the p‐n junction. Comparison of the experimental results with the Shockley‐Read theory indicates that within the range Δ = 0.5 to 6, recombination takes place via donor‐type centres (σn/σp = 1.7) situated (0.36 ± 0.02) eV above the edge of the valence band. These levels are therefore attributed to atoms of gold in the p‐Si.
Bubble Diffusion and the Motion of Point Defects near Surfaces. (Diffusion Theory for Discrete Media, Part IV
Authors: Kelly R. 
Published: July 2007

AbstractThe theory of diffusion of inert‐gas bubbles in solids is important in a variety of fields, including reactor technology, ion bombardment, powder metallurgy, and the study of large defects. Bubble diffusion also provides a convenient frame of reference for discussing the motion near surfaces of point defects, i.e. of surface defects, vacancies, and vapourized atoms or molecules. It is shown that the bubble diffusion coefficient, Db, for a surface‐diffusion mechanism is equal to (3/2 π a4) Ds, where a is the bubble radius in units of λ, the mean atomic spacing, and that this expression is independent of the surface‐diffusion jump distance. The formation of vacancies at a surface should occur at a frequency given by Γfv = Dvol α/f pvλ2 per area λ2 of the surface, where αv is the vacancy condensation efficiency, f is the correlation factor, and pv (in units of λ) is the atom layer spacing next to the surface. With this assumption, Db for a volume‐diffusion mechanism will be equal to (3/2 π a3 f) Dvol. The frequency at which vapourized atoms or molecules are formed is shown to be given by a relation very similar to that for vacancy formation. The corresponding expression for Db, i.e. that for a vapourization‐condensation mechanism, is of the form (3/4 π a3) (Dg Cg λ3), where Dg is the vapour diffusion coefficient and Cg is the equilibrium vapour concentration in atoms/cm3.
Preparation of Cu2Se Single Crystals and Investigation of their Electrical Properties
Authors: Abdullaev G. B. , Aliyarova Z. A. , Asadov G. A. 
Published: July 2007

AbstractA study is made of the electrical conductivity, σ, the thermo e.m.f., α, and the Hall constant, R, in single crystals of Cu2Se. The temperature dependence of these phenomena in the range 22 to 650 °C is also investigated. From the temperature dependence of σ a value of 1.2 eV is found for the activation energy, ΔE, in the inherent region, whereas the value obtained from the optical absorption edge is 1.3 eV.
Fließspannung und Versetzungsdichte Kalzium‐dotierter NaCl‐Einkristalle
Authors: Hesse J. 
Published: July 2007

AbstractKalzium‐dotierte NaCl‐Einkristalle werden im dynamischen Druckversuch verformt. Die Änderung der Verfestigungskurve (VK) und des Zusammenhangs von Versetzungsdichte N und Schubspannung τ mit dem Ca‐Gehalt werden bestimmt. Die VK erweist sich als dotierungsabhängig: Der Verfestigungsanstieg im Bereich I und die Länge dieses Bereichs nehmen mit steigendem Ca‐Gehalt zu. Der Verfestigungsanstieg im Bereich II ist dagegen von der Dotierung unabhängig. Der lineare Zusammenhang von τ und N, der für “reines” NaCl erst im Bereich II gefunden wird, setzt für Ca‐dotiertes NaCl schon im Bereich I ein. Für Ca ⪆ 60 ppm gilt dann τ ∼ N bereits an der kritischen Schubspannung. Diese Ergebnisse werden in Verbindung mit der Temperaturabhängigkeit der Verfestigungsparameter diskutiert.
The Geometry and Energy of a Twist Boundary between Crystals with Unequal Lattice Parameters
Authors: Jesser W. A. , Kuhlmann‐Wilsdorf D. 
Published: July 2007

AbstractThe geometry of “twist‐misfit boundaries” is investigated. These are dislocation networks such as arise in the interfaces between epitaxial overgrowths and substrates with unequal lattice parameters when they are slightly twisted relative to each other with respect to an axis normal to the interface. In the particular cases examined the interface has simple cubic or close‐packed hexagonal symmetry. By introducing the equations obtained for the dislocation spacings and orientations into the theory of interfaces developed by Frank and van der Merwe, the interfacial energy is calculated as a function of misfit and twist. By further combining the expressions thus derived with the theory of Cabrera, the equilibrium elastic strain in hemispherical epitaxial nuclei on infinite substrates is calculated. This is found to decrease with increasing size and with increasing misalignment of the nuclei. Because of the complexity of the equations, all numerical computations were performed with a B 5500 computer.