bluuebunny/crossref_metadata_2025_split huggingface dataset:
Angular Dependence of the Ti K Edge in Rutile TiO2
Authors: Poumellec B. , Cortes R. , Tourillon G. , Berthon J. 
Published: July 2007

AbstractThe angular dependence is investigated of the X‐ray absorption spectrum of TiK edge in TiO2 recorded in the total electron yield mode. Despite the weak distortion of the octahedral coordination, the absorption spectra exhibit wide contrast which enables designation of the excited state orbitals involved in the strong transitions. The energy splittings between the degenerate transitions in perfect octahedral symmetry are much more pronounced than could be expected from a one‐electron ground state analysis. It is deduced that the first allowed transitions (i.e. 1s → 4p) seem to show sensitive dependence on the local symmetry. However, for the weak transitions before the edge, the analysis is not straightforward and is still in progress.
19F NMR study of the fluorite‐Type Ca1−xThxF2+2x solid solution
Authors: Suh Kyung‐Soo , Senegas J. , Reau J. M. , Hagenmuller P. 
Published: July 2007

AbstractAn investigation is made by 19F NMR of the disordered fluorite‐related solid solution Ca1−xThxF2+2x (0 ≦ x ≦ 0.18). The existence is shown of different fluoride sublattices at low temperatures and the setting‐up of partial exchanges between them at increasing temperature. The identity of these sublattices with those identified by neutron diffraction is discussed. The NMR study allows to confirm the formation of clusters of 1:0:3 type in Ca1−xThxF2+2x. The results obtained are so in good agreement with the composition dependence of the ionic conductivity properties and are satisfying with respect to the model of the processes of clustering proposed for the anion excess CaF2‐type solid solutions: indeed, within Ca1−xThxF2+2x, the F‴ interstitial fluoride ions seem to play the main role in the long‐range motions.
The influence of surface states on the photovoltage of real silicon surface
Authors: Schulz J. , Würfel P. , Ruppel W. 
Published: July 2007

AbstractThe surface photovoltage caused by band‐to‐band generation within the semiconductor depends on light intensity. This dependence differs significantly in two limiting cases. When recombination via fast surface states is negligible, the slope of the photovoltage versus the logarithm of intensity is always less than kT/e and depends on the amount of semiconductor band bending in the dark. When recombination via fast surface states becomes strong, this slope is kT/e, independent of the band bending. These differences are experimentally observed using a structure with ferroelectric NaNO2 deposited on a real silicon surface. The switching of the direction of the spontaneous polarization of the ferroelectric results in significant changes of the semiconductor band bending in the dark. The charge exchange with slow surface states results in a continuous change of the band bending in the dark. The measurements reveal a pronounced minimum of the density of fast surface states near mid‐gap. The results compare well to those from measurements on a field effect transistor structure with NaNO2 as gate insulator.
MT effective medium approximation in R‐representation for the electron structure of 3d metals
Authors: Ya. Asanovich V. , Miklashevich I. A. 
Published: July 2007

AbstractA continuum model for the electron structure of 3d melted metals in coordinative submission is proposed. The electron state density n(E) is defined by site scattering matrix tj, Green functions, and derivatives from these figures. The nearest — neighbour order is evaluated with the help of radial distribution scatterers g(r). The d‐bond of Fe is filled in partly, and its width is about 0.2 Ry. This figure is a little bit more then in cluster models. The peak width is connected with a more correct calculation of the nearest — neighbour order.
Electron‐energy‐loss spectroscopy of a n—i—p—i semiconductor superlattice
Authors: Albuquerque E. L. , Farias G. A. , Auto M. M. 
Published: July 2007

AbstractA semi‐infinite superlattice structure consisting of a periodical array of n‐ and p‐doped semiconductors layers intercalated by an insulator is considered and it is examined how the electron‐energy‐loss spectroscopy can be used to probe the spectra of surface plasmon modes which propagate in these structures. A backscattering geometry is used for the scattered electron and a semiclassical theoretical approach for interpreting the electron‐energy‐loss spectra.
Self‐consistent states of a flow of quasi‐particles and immobile deformation in one‐dimensional systems
Authors: Ermakov V. N. , Ponezha E. A. , Tkach V. I. 
Published: July 2007

AbstractNew solutions are obtained of a set of two‐component nonlinear equations that correspond to a self‐consistent state of moving quasi‐particles and immovable deformation. The deformation is a periodic structure that consists of potential wells. It is shown that in the case considered the effective mass of carriers is determined by the probability of tunneling and may rise appreciably.
Static Skin Effect at High Current Densities
Authors: Oyamada K. , Peschanskii V. G. , Stepanenko D. I. 
Published: July 2007

AbstractThe nonlinear effects in the conductivity of metals and intrinsic semiconductors placed into a homogeneous magnetic field H0 are investigated under the conditions of the static skin effect. The electric current distribution and the intrinsic magnetic field of the current Hj in the sample are obtained by the asymptotic solution of the system of Maxwell and kinetic equations in the case of a slowly changing total magnetic field over a distance of the order of the electron Larmor radius. It is shown that by varying H0 one can study separately the dynamic nonlinear effect associated with the Hj influence on the ballistics of conduction electrons, and the deviation from Ohm's law due to charge carrier heating by electric current.
On the Possibility of Exchange Induced Pairing Mechanism in Model Heavy Fermion Superconducting Systems
Authors: Ghosh S. C. , Ghosh N. K. , Sarkar R. L. 
Published: July 2007

AbstractThe periodic Anderson model extended by exchange induced non‐phononic pairing interaction between f‐ and d‐electrons is investigated in the context of singlet like superconductivity. d–d, f–f, and f–d pair density functions are calculated and the stability of different pairing due to various interactions are studied. f–d cross‐over effect is observed and the exchange interaction is found to have the effect of stabilising the pairing; low temperature specific heat is calculated and explained.
Thermal Quenching of the Eu2+ Photoluminescence in KCl and NaCl Crystals
Authors: Sokólska I. , Mugeński E. 
Published: July 2007

AbstractThe photoluminescence spectra, lifetimes, and intensity of emission of Eu2+ are examined for KCl:Eu2+ and NaCl:Eu2+ crystals within the range of 15 to 800K. The quantum yield of emission related to the dipoles and aggregation products formed up to 400 K is found to be temperature independent. Thermal quenching of the emission related to the aggregation products formed at 425 to 525 K is explained by the two‐channel nonradiative de‐activation of excited t2g(4f65d) levels.
X‐Ray K‐Absorption Edge Shift of Copper in Some of Its Compounds and Organo‐Metallic Complexes
Authors: Pandey S. K. , Chetal A. R. 
Published: July 2007

AbstractChemical shift, ΔE, of the X‐ray K‐absorption edge is measured in some compounds and organometallic complexes of copper possessing formal oxidation states 1+ and 2+. The best fit correlation between the chemical shift, ΔE, and the effective charge, q, using the least‐squares regression analysis procedure is found to be a non‐linear equation ΔE = Aq + Bq2 + Cq3, where A, B and C are constants. In the light of statistical treatment it is shown that the effective charge, q, is a significant explanatory factor of the variation in the X‐ray absorption chemical shift, ΔE. Interpretations to the variations in X‐ray absorption chemical shift are also given on the basis of electronegativity, oxidation state, the valence d‐orbital electrons, atomic number, crystal structure, etc.
Raman Spectra of [N(CH3)4]2ZnCl4 Single Crystals I. Raman Spectra of the Parent Phase
Authors: Torgashev V. I. , Yuzyuk Yu. I. , Rabkin L. M. , Durnev Yu. I. , Latush L. T. 
Published: July 2007

AbstractPolarized Raman spectra of [N(CH3)4]2ZnCl4 crystals are studied in phase I in the frequency range between 10 and 3500 cm−1. An assignment of the lines observed to motion types is carried out. The sublattice of the TMA ions is found to behave as a quasi‐liquid. The distorsion of the ZnCl tetrahedra is insignificant. A considerable orientational disorder is shown to occur in this phase.
Helical Nature of Collective Excitations in α‐Helical Protein
Authors: Ichinose S. 
Published: July 2007

AbstractCollective excitations in long α‐helical proteins are investigated, including two types of peptide groups displacements provided by changes of the helix pitch and its radius. It is shown that the motion of asymmetric excitations along the protein molecule have a helical nature. For these excitations there occurs an exchange of excitations between chains as a result of the resonance interaction between peptide groups belonging to different chains.
Vortex Nucleation in Thin Film of an Uniaxial Anisotropic Superconductor
Authors: Krzysztoń T. 
Published: July 2007

AbstractIn the framework of London theory the problem of vortex nucleation in a thin film of an anisotropic superconductor is studied. The Gibbs free energy of a vortex as a function of its distance from the surface of the film is calculated. This energy is considered as a surface barrier opposing penetration of the vortices into the film. The barrier disappears when a certain value of external magnetic field – the field of first penetration – is applied. The strength of this field is calculated as a function of an angle between the anisotropy axis and the direction of external magnetic field.
Phonon‐Polaritons in Isotropic Ferromagnets I. The Influence of the Magnetization on Surface Phonon‐Polaritons
Authors: Dimitriev O. P. , Lozovskii V. Z. , Getsko O. M. 
Published: July 2007

AbstractIn the frame of a phenomenological approach the propagation of phonon surface polaritons (SP) on an isotropic isolator having non‐zero magnetization is considered. Dispersion relations of SP are presented for following orientations of the magnetization: 1) magnetization in the surface plane and perpendicular to the wave vector of SP; 2) magnetization parallel to the wave vector of SP; 3) magnetization perpendicular to the surface plane It is shown that for the two last geometries new SP arise which are not TM‐waves, and their properties are dependent on the values of medium magnetization and applied magnetic fields.
Temperature Dependence of the Structure Factor of Liquid Alkali Metals
Authors: Nigam S. K. , Khanna K. N. 
Published: July 2007

AbstractThe temperature dependence of the structure factor, S(q), of liquid alkali metals is studied using a Percus‐Yevick‐tail reference system including a Cummings potential in a random phase approximation. The Cummings potential parameters, determined at the melting temperature for each metal are also used at higher temperatures and are found to be related to the atomic number of the metal.
Self‐Diffusion in Crystals
Authors: Buchbinder G. L. 
Published: July 2007

AbstractThe mobility of a vacancy in the lattice is considered. The jump of the vacancy is interpreted as a transition of the system from some quantum state with localized vacancy into another one in which the vacancy is localized at a neighbouring site. The expression for the jump rate W is obtained. At high temperatures the temperature dependence of W describes an activation process with an activation energy defined by the second moment of the frequency distribution function of the defective crystal. At low temperatures the influence of resonant modes on mobility of the vacancy is considered.
Disclinations in Heterogeneous Small Particles
Authors: Gryaznov V. G. , Kaprelov A. M. , Polonskii I. A. , Romanov A. E. 
Published: July 2007

AbstractElastic effects in elastically inhomogeneous pentagonal small particles are analyzed. Two continual elastic models are applied and considered in detail: a wedge Frank disclination in an infinite elastic cylinder consisting of two coaxial layers of different phases and a Marks‐Yoffe disclination in an elastic sphere consisting of two concentrical layers of different phases. The corresponding boundary problems are solved. It is shown on the basis of these solutions that the disclination–interface elastic interaction stimulates interface migration and hence may either promote or retard phase transformation processes. Disclination elastic fields may initiate dislocation generation at the interface and cause a point‐defect diffusion flux resulting in an inhomogeneous distribution of impurities in the particle.
Existence of Two‐Phonon Bound States in Deuterated Naphthalene
Authors: Bhandari R. , Jindal V. K. 
Published: July 2007

AbstractA numerical calculation is performed to search for the existence of two‐phonon bound states in deuterated naphthalene crystals. The quartic anharmonic force constant needed for the calculation of the poles in the two‐phonon Green's function is approximated by using Peierls approximation and already calculated results of the explicit anharmonic shifts to the phonon frequencies. The results indicate that the existence of two‐phonon bound states is possible in a deuterated naphthalene crystal at various temperatures.
Approximation of Local‐Field Effects in the Dielectric Formalism of Lattice Dynamics
Authors: Falter C. , Klenner M. , Ludwig W. 
Published: July 2007

AbstractThe phonon dispersion is investigated of a crystal where local field effects are taken into account using a first‐order perturbation expansion with respect to the off‐diagonal of the dielectric matrix. Such an expansion is used in other applications in the literature. It is shown that a straightforward application of this approach is not sufficient for a proper description of acoustic phonons in semiconductors and insulators in the limit of long wavelength because the acoustic sum rule is violated. A general expression for the correction term being of second order is given. Furthermore, the relations are illustrated with the phonon dispersion and certain phonon induced polarization charge densities in Si using a suitable model for the dielectric function.
The Time‐Dependent Ising Model on the 2D Penrose Lattice
Authors: Doroba A. , Sokalski K. 
Published: July 2007

AbstractThe kinetics of the Ising model on the 2D quasicrystal (Penrose) lattice is investigated. On the base of the Glauber method the system of the differential equations describing the temporal evolution of the expectation values of the averages of spins occupying the vertices of the Penrose “kite and dart” lattice is constructed. The mean field approximation, modified for the case of the nonperiodic system is applied. The stationary solution and their stability are discussed. The time‐dependent solutions of the problem in the case of the ferromagnetic and antiferromagnetic couplings between spins are found. The qualitative changes of the attractors under the changes of the external parameters are analysed. The limitations of applying the mean field approximation for the problems of the kinetics are discussed.
Scattering of Laser Light by an Acoustic Wave in Magnetoactive Noncentrosymmetric Semiconducting Crystals
Authors: Jat K. L. , Ghosh S. 
Published: July 2007

AbstractConsidering that the origin of nonlinear interaction lies in the second order optical susceptibility arising from the nonlinear induced current density and using the coupled mode theory, an analytical investigation of scattering of laser by acoustic wave and the consequent amplification of scattered modes and acoustic wave is carried out in a transversely magnetised semiconductor of noncentrosymmetric nature. The influence of carrier density is also considered. The threshold value of the pump electric field is obtained. Eoth is found to decrease with increasing magnetic field and decreasing scattering angle. The steady state growth rates for piezoelectric (gp) and deformation potential (gd) scattering and both (gb) ones are also obtained. The numerical estimations are made for n‐InSb crystals at 77 K. The gain constants are found to be higher in the presence of a strong magnetic field when the cyclotron frequency is near to the pump frequency. The doping level is also found to have a significant influence on the gain constant.
Bi2 Te3 Crystals Heavily Doped with Tin Atoms
Authors: Horák J. , Lošťak P. , Geurts J. 
Published: July 2007

AbstractThe values of transport coefficients (Hall constant and Seebeck coefficient) of Bi2Te3 crystals strongly doped with Sn atoms are determined at room temperature. From reflectivity measurements in the IR region, the plasma resonance frequency ωp, relaxation time τ, and high frequency permittivity are found. The interpretation of the results obtained in the concentration interval, 0 < x < 3 × 1020 Sn atoms per cm3, leads to the conclusion that one part of the Sn atoms incorporated enters into the bismuth sublattice giving rise to negatively charged substitutional defects Sn'Bi, the other part forms uncharged defects. The formation of uncharged defects produced by the incorporation of Sn‐atoms into the Bi2Te3 crystal lattice is explained in the following way: Sn‐atoms form seven‐layer‐lamellae of the composition Te‐Bi‐Te‐Sn‐Te‐Bi‐Te which corresponds to the structure of the SnBi2Te4 compound; this seven‐layer‐lamella is uncharged. The formation of such a seven‐layer‐lamella can easily explain the experimental results: Sn‐atoms incorporated into the seven‐layer‐lamella are electrically inactive.
Energy‐Dependent Connection Rules of Envelope Functions at Heterointerfaces
Authors: Paasch G. , Nguyen P. H. , Gobsch G. 
Published: July 2007

AbstractIt is shown that the energy‐dependent connection rule of Bastard can be derived in a simple manner. The method can be generalized to more general ones than the Kane band structure. Moreover, starting from a complete two‐band model a classification of different former approaches of connection rules is presented and that one of Ishibashi et al. is derived with less restrictions and in a simple way. It is shown that the use of the two‐band model modifies the tunneling probability as it is usually calculated from a one‐component description.
The Biexciton Influence on Bose‐Einstein Condensation of Orthoexcitons in Cu2O
Authors: Bobrysheva A. I. , Moskalenko S. A. , Russu S. S. 
Published: July 2007

AbstractThe influence of the biexcitons formed from two orthoexcitons on the Bose‐Einstein condensation (BEC) of orthoexcitons and the possibility of the BEC of biexcitons is studied theoretically. It is shown that the existence of biexcitons in Cu2O crystal leads to a considerable difficulty for the observation of the BEC of orthoexcitons. The lineshape of the net gain of biexciton transition in Cu2O crystal is calculated. The obtained line is characterized by a strongly marked asymmetric form with a gentle sloping long‐wave tail and a sharp peak which is peculiar to BEC of biexcitons.
Electronic Structure of Point Defects in Semiconductor Alloys
Authors: Das A. , Barbero C. J. , Singh V. A. , Corbett J. W. 
Published: July 2007

AbstractA simplified tight‐binding approach based on the coherent potential approximation (CPA) formalism is presented for the host electronic structure of semiconductor alloys (e.g. Ga1−xAlxAs). Several schemes to locate the gap level due to point defects are discussed. In particular, a novel scheme is introduced: the deep level approximation (DLA). It is pointed out that the vacancy results in the CPA are identical to the simpler virtual crystal approximation (VCA). In addition, the electronic band structure of SixGe1−x alloys is presented using a non‐orthogonal tight‐binding approach, namely the extended Hückel theory (EHT). Preliminary calculations of the dependence of the band gap on concentration are also presented.
Molecular‐Field Theory Analysis of Rare‐Earth Ternary Carbides Derived from R2Fe17 Compounds
Authors: Qiao W. H. , Wang Q. , Zhong X. P. , Luo H. L. 
Published: July 2007

AbstractOn the basis of a two‐sublattice model, the temperature dependent magnetic properties of the intermetallic compounds R2Fe17C (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Lu) are analyzed using the molecular‐field theory. The results of the analysis show that the molecular‐field coefficients nRF are rather sensitive to the kind of the rare earth spin, but the spin‐exchange parameters ARF hardly change. The intersublattic molecular (ISM) field H and the spin‐exchange field H are calculated, the results are compared with other ones and discussed.
The Continuous Background of SERS from Ag Colloids in Alkali Halide Crystals
Authors: Abel H.‐B. , Fischer F. 
Published: July 2007

AbstractThe continuum background of the SERS spectrum from thermally or photochemically prepared Ag colloids in alkali halide crystals is studied from − 5000 to + 1400 cm−1 and for counting rates covering three decades. The Stokes side consists of three contributions extending to about − 1500, − 3800, and beyond − 5000 cm−1 for 488 nm exciting light. As long as there is no evidence for hot luminescence it may be interpreted as SERS caused by charge‐transfer from the Fermi sea of the silver to mobility states and band‐tail states of the host and to localized surface states of the colloid. The anti‐Stokes intensity of the continuum background is found to follow a Boltzmann law between room temperature and 80 K.
Dipole Tensors and Volume Changes of Point Defects in H.C.P. Lattices
Authors: Monti A. M. 
Published: July 2007

AbstractBy computer simulation techniques dipole tensors and relaxation volumes of point defects in h.c.p. lattices are calculated for the fully relaxed lattice. Short‐range pair interatomic potentials to represent Mg and α‐Zr are used. Calculations for the vacancy at its equilibrium and activated states are reported. Quantitative differences due to the material elastic properties are found. For self interstitials, dipole tensor symmetries and volume‐change values are analyzed taking into account the defect‐lattice symmetries.
Generation of LO‐Phonons in a Time‐Dependent Electric Field at the Surface of III – V Materials
Authors: Scholz R. , Stahl A. 
Published: July 2007

AbstractRecent experiments with ultrashort light pulses have shown that in the semiconductor samples under study the surface field is screened so quickly that it can generate coherent LO‐phonons. A theoretical description of this effect necessitates the simultaneous consideration of a number of interacting quantities: the exciting light field, the time dependent distributions of electrons and holes evolving towards equilibrium, the LO‐phonon amplitude, and the electric field self‐consistent with monopolar and dipolar charges. It turns out that the wave‐like nature of electronic distributions plays a decisive role via quantum mechanical boundary conditions. In the theory presented here this is accounted for by the use of a real space density matrix description.
The Role of the Electron‐Hole System in the Thermodynamics of YBa2Cu3O7−δGas Equilibrium
Authors: Tsidilkovskii V. I. , Leonidov I. A. , Lakhtin A. A. , Mezrin V. A. 
Published: July 2007

AbstractThe YBa2Cu3O7−δ‐gas equilibrium is studied theoretically in terms of the approach proposed earlier by the authors. The contribution of the electron‐hole system of the HTSC oxide to the equilibrium thermodynamics is studied for several models of the electronic structure. Oxygen—oxygen interactions in the basal plane are taken into account to calculate the chemical potential of oxygen ions in the oxide, distinct from the previous paper where these interactions are disregarded. It is shown that the equilibrium is well described for a sufficiently broad (much broader than kT) valence band with a hole effective mass mp ≈ 3 to 5 free electron masses.