bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monte Carlo Simulation Analysis of Proton‐Energy Spectra for Axial Channeling in Silicon in the Intermediate Energy Region
Authors: Lenkeit K. , Trikalinos Ch. , Balashova L. L. , Kabachnik N. M. , Shulga V. I. 
Published: July 2007

AbstractA detailed theoretical analysis of experimental energy spectra of axial‐channeled protons transmitted through thin silicon targets is performed by Monte Carlo calculations. Energy spectra are calculated for 〈110〉, 〈111〉, and 〈112〉 channels in the energy region from 50 to 300 keV. The Monte Carlo program is based on the continuum string model. The energy loss on valence electrons is calculated on the basis of a modified Lindhard model for channeling energy loss and the stopping number is taken from the local density approximation of the Lindhard‐Winther formalism. The anisotropic distribution of the valence electron density in a semiconductor is taken into account. Stopping due to core electrons is considered by a semiclassical approximation. Multiple scattering and energy straggling are included in the simulation program. The calculated energy spectra and channeling stopping powers are in good agreement with experimental ones.
LCAO Recursion Approach in k‐Space Representations for the Treatment of Bulk and Surface Problems
Authors: Hergert W. , Rennert P. 
Published: July 2007

AbstractThe recursion method in a k‐space representation is used to calculate the electronic density of states for bulk and surface problems. The separability property of the Hamiltonian and the Green function is consequently used to avoid the discussion of the asymptotic behaviour of the recursion coefficients. The results of the recursion calculations in k‐space representation are compared with recursion calculations in a local basis and conventional LCAO calculations. Results are presented for silicon. The connection of local and k‐space representations for the treatment of adsorbate systems is discussed.
Microscopic Derivation of a Transport Equation for the Acoustic Polaron
Authors: Liu S. , Sak J. 
Published: July 2007

AbstractStarting with the Kubo formula, a transport equation for the acoustic polaron is derived. The collision integral in the transport equation contains not only irreducible vertex parts, but also “products” of them. These are products of irreducible verteces connected by non‐singular parts of Green's functions. They are important when one considers the second or higher order perturbations, as in the case of an acoustic polaron at very low temperatures.
Spin–Lattice Coupling Coefficients Gij for Trigonal Al2O3:Fe3+ and ZnSiF6 · 6H2O:Ni2+ Crystals2)
Authors: Zheng Wen‐Chen 
Published: July 2007

AbstractBy expressing the six spin–lattice coupling coefficients G in trigonal symmetry in terms of the coefficients G and G in cubic symmetry, the coefficients G for trigonal Al2O3 : Fe3+ and ZnSiF6 · 6 H2O : Ni2+ crystals are calculated from the values of G and G obtained from a simple and uniform method within the framework of cubic symmetry approximation. The results for the Al2O3 : Fe3+ crystal is in agreement with the experimental findings, whereas for ZnSiF6 · 6 H2O : Ni2+, the agreement for part of coefficients is poor. The reasons for the disparity are discussed.
On the Carrier Spectrum of CuO2 Planes in High‐Tc Superconductors and Its Dependence on Stoichiometry
Authors: Loktev V. M. 
Published: July 2007

AbstractAn attempt is made to analyse the problem of the conduction band type (σ or π) in HTSC copper oxides. It is established that the σ‐character of this band may take place only under the condition of strong pd‐hybridization between p‐ and d‐holes from the upper Hubbard subband. The effect of nonstoichiometry on delocalized carriers consists in a possible appearance of discrete levels or a change in the spectrum as a whole. The estimate of these carriers damping as a function of nonstoichiometry shows that the damping may be a nonmonotonous function of doping that makes it possible to speculate of various HTSC properties dependent on lattice disordering.
Superconducting Current in a Bisoliton Superconductivity Model
Authors: Ermakov V. N. , Kruchinin S. P. , Ponezha E. A. 
Published: July 2007

AbstractIt is shown that the transition into a superconducting state with the current which is described by a bisoliton superconductivity model is accompanied by the deformation of the spectrum of one‐particle states of the current carriers. The deformation value is proportional to the conducting current force. The residuary resistance is absent in such states.
The Capture of an Extra Electron by Supersonic Acoustic Solitons in a Molecular Chain in the Presence of Thermal Vibrations
Authors: Kadantsev V. N. , Lupichev L. N. 
Published: July 2007

AbstractThe possibility for an extra electron to be transferred by a supersonic acoustic soliton in a thermalized one‐dimensional (1D) lattice with quintic anharmonism is studied. Existence conditions for solitonic solutions and electron states in a distorting potential produced by the acoustic soliton are analyzed. The effect of thermal vibrations of the molecules on the state of an extra electron held by a periodic molecular chain is demonstrated.
Absorption of Impurity Centres of a Crystal in the Field of a Strong Monochromatic Wave
Authors: Apanasevich P. A. , Kruglov V. I. , Tralle I. E. 
Published: July 2007

AbstractOn the basis of the non‐Markovian kinetic equation the nonlinear susceptibility and the absorption coefficient are investigated for different models of the impurity centre and electron—phonon interaction in the field of a strong electromagnetic wave. An analytical expression is obtained for the nonlinear absorption coefficient which differs greatly from the formula of the Bloch theory.
Accurate Numerical Calculation of the Electron Density at a Bijellic Interface within the Gradient Expansion Method
Authors: Kaschner R. , Vojta Th. 
Published: July 2007

AbstractThe differential equations of the gradient expansion method (concerning corrections to the kinetic, exchange, and correlation energies of the local density approximation) for the electron density at a bijellic interface are solved accurately by means of a discretization of the Euler and Poisson equations. The resulting set of nonlinear algebraic equations is solved by iteration (Newton‐Raphson method). The results are checked by means of several rigorous theorems. The accuracy of earlier approximate solutions of this problem is estimated. A comparison of the adhesive forces with the results of Vannimenus and Budd is performed.
Induced Absorption Spectroscopy by Lattice Defects in Sillenite‐Type Crystals
Authors: Efendiev Sh. M. , Gavryushin V. , Raciukaitis G. , Bagiev V. E. , Kazlauskas V. , Puzonas G. , Aliev R. A. , Mustafaev E. R. 
Published: July 2007

AbstractIn sillenite‐type crystals. Bi12XO20 (BXO) (X = Si, Ti, Ge), the effects of laser modulation of two‐step absorption (LM TSA) by deep local centres with spectroscopic regularities common to all the crystals of such type are observed. It is shown that to explain the nature of LM TSA, the indirect energy‐band structure of such crystals and the direct optical transitions from strongly localized states of deep defects extending in k‐space both, to “indirect” minimum and “direct” extremum of the conduction band should be taken into account. In sillenite‐type crystals the LM TSA processes involve intercenter optical transitions from the states of dominant intrinsic defects of extremly great concentration.
Phonon Spectrum of the One‐Dimensional Two‐Component Quasiperiodic Crystal
Authors: Gumen L. N. , Usatenko O. V. 
Published: July 2007

AbstractThe properties of an one‐dimensional quasicrystal consisting of two types of atoms with masses m and M, and with nearest neighbour elastic interaction constants k and K, are studied. The velocity of long‐wavelength phonons and the dependence of the maximum oscillation frequency on lattice parameters are derived analytically. The classification procedure of quasicrystal spectra is performed in the limit of large difference of masses and elastic constants. Five different limiting kinds of the spectra are shown to occur.
Electronic Structure and Thermodynamic Properties of PdHx
Authors: Anagnostaras P. , Sikakana I. , Lowther J. E. 
Published: July 2007

AbstractThe cluster‐Bethe model developed for the electronic and cohesive properties of nonstoichiometric palladium hydride is now extended to compute thermodynamic properties. A plateau region in the computed isotherms is seen to emerge consistent with that suggested from observed hydride behaviour. The model is employed to give the critical concentration of hydrogen at which the gas will leave the metal. Results are presented for a range of different temperatures.
Temperature Variation of Optical Energy Gap and Deformation Potentials in AgInTe2
Authors: Quintero M. , Tovar R. , Bellabarba C. , Woolley J. C. 
Published: July 2007

AbstractValues of the optical energy gap E0 of AgInTe2 as a function of temperature T in the range 10 to 300 K are obtained by optical absorption measurements. The variation of E0 with T is fitted well by a Manoogian‐Leclerc equation of the form E0(0) − E0(T) = UT + Vφ (coth φ/2T − 1). Values of (dE0/dT)1, the electron–phonon interaction contribution to the variation of the energy gap with temperature, and (dE0/dT)2, the lattice dilation contribution, are obtained from the Vφ and U terms, respectively. From these values of (dE0/dT)1 and (dE0/dT)2, values are determined for the acoustic deformation potentials of the conduction band Ce and the valence band Ch.
Spectroscopic Properties of Pr3+ and Nd3+ Ions in Zinc Tellurite Glasses
Authors: Kanoun A. , Alaya S. , Maaref H. 
Published: July 2007

AbstractThe optical absorption and emission of Pr3+ and Nd3+ ions in 1 ZnO, 2 TeO2 glasses are measured in the visible and near‐infrared region and an energy level scheme is established. The intensity parameters (Ω2, Ω4, Ω6) are calculated using the Judd‐Ofelt formulae. Using these parameters and the matrix element of Pr3+ and Nd3+ oscillator strengths, transition probabilities, and branching ratios are obtained.
Picosecond Photoconductivity Studies on Phenyl‐Substituted Poly (Phenylenevinylene) Derivatives
Authors: Li Haoliang , Rentsch S. , Yang Jiping , Lenzner M. , Bergner H. 
Published: July 2007

AbstractTime resolved transient photoconductivity (PC) measurements are performed on phenyl‐substituted poly (phenylenevinylene) (P‐PPV) derivatives and one oligomer. The photogenerated carriers are assigned to be polarons and bipolarons, which are responsible for the picosecond and nanosecond PC components, respectively. By a deconvolution procedure the relaxation times are obtained for both components. The PC, the mobility, and the migration distance of carriers are obtained. Polymer and oligomer exhibit nearly the same value of electrical mobility. The hopping mechanism of carriers in the P‐PPV seems to be the dominating process for PC.
On the Critical State and Surface Barrier of a Type II Superconducting Long Cylinder
Authors: Saif A. G. , Refai T. F. 
Published: July 2007

AbstractThe creation and annihilation of the surface barrier in the frame of the general critical state theory of a type II superconducting long cylinder is studied. It is shown that the value of the superheating field is reduced when a transport current is allowed to flow along the cylinder's axis.
The Ising Antiferromagnet with Competing Interactions. Locating the Tricritical Point
Authors: Jäger I. 
Published: July 2007

AbstractA thorough Monte Carlo investigation of the critical surface of the Ising antiferromagnet in the region of competing interactions is made with special respect to the location of the tricritical point. Results are that presumably the tricritical point is located at its Onsager value J2 = −0.4407kT not only for J1 = 0 but for all J1 (antiferro) and the tricritical field attains the value HT = 4J1 asymptotically. A drawing of the critical surface in the J1/kT−J2/kT−H/kT space is given.
EPR of a VO2+‐Doped Fe(NH4)2 (SO4)2 · 6H2O Single Crystal. VO2Fe2+ Exchange Interaction and Spin–Lattice Relaxation Time of Host Fe2+ Ions
Authors: Misra Sushil K. , Sun Jiansheng , Orhun U. 
Published: July 2007

AbstractX‐band (≈9.5 GHz) electron paramagnetic resonance (EPR) studies of the VO2+ ion are carried out on a single crystal of the Tutton salt Fe(NH4)2(SO4)2 · 6H2O (FASH) at 295, 80, and 4.2 K. The data indicate two physically‐equivalent VO2+ sites in the unit cell, each consisting of three magneticallyinequivalent VO2+ ions. The principal values and direction cosines of the principal axes of the g2 and A2 tensors are evaluated, using a least‐squares‐fitting program. An impurity [VO(H2O)5]2+ complex model of the vanadyl ion is found to explain the data well. The V4+O2− bond directions for the VO2+ ions are deduced. The VO2+Fe2+ exchange‐interaction constant in FASH is estimated. The host‐ion (Fe2+) spin‐lattice relaxation time is estimated from VO2+ EPR linewidth.
Charge Distribution of Electrons at Intercalated Atoms in Layer Crystals
Authors: Lukiyanets B. A. 
Published: July 2007

AbstractThe charge distribution of electrons at intercalated atoms in a layer crystal is considered in the two‐impurity model of the Anderson type. The dependence of this distribution on the Coulomb interaction between intercalants and on the electron mixing of the intercalate–intercalant system is analyzed.
Theory of Germanium‐Related Defects in Vitreous Silicon Dioxide [GeO4]−‐Center
Authors: Dianov E. M. , Sokolov V. O. , Sulimov V. B. 
Published: July 2007

AbstractThe properties of the anisotropic paramagnetic [GeO4]− center (tetrahedral coprdinated Ge substitutional atom with an electron trapped) in vitreous silicon dioxide are investigated in a cluster approach by means of the MNDO quantum‐chemical method taking the atomic relaxation into account.
On the Energy Transfer in the Thermally Annealed KCl: Pb2+, Eu2+ System
Authors: Muñoz‐Santiuste J. E. , García‐Solé J. , Manfredi M. 
Published: July 2007

AbstractPb → Eu energy transfer mechanisms in the thermally annealed KCl: Pb2+, Eu2+ system are examined by means of optical absorption, emission, and time decay spectra of the luminescence. The thermal annealing produced the formation of the Pb2+ Suzuki phase and the results show that the Eu2+ ions enter this phase by substituting for some Pb2+ ions. The Pb → Eu transfer is found to be a very efficient process, with a very short transfer time. The analysis of the time decay signals shows that the transfer is a single pair mechanism; no migration of the excitation energy is experimentally detected.
High‐Temperature Equilibrium between High‐Tc Oxide and Gas Phase
Authors: Tsidilkovskii V. I. , Leonidov I. A. , Lakhtin A. A. , Mezrin V. A. 
Published: July 2007

AbstractThe equilibrium between the high‐Tc oxide YBa2Cu3O7‐δ and the gas phase is studied for some models of the ioic and electroic (e.g., two‐band model) systems of the compound. The calculations show that the contribution of the electron‐hole system to this equilibrium is essential. The comparison of the theory with experiment allows to obtain such paramenters as binding energy of oxygen ions, their effective Einstein frequency Δ, the hole effective mass mp, etc., the Δ and Mp values being in agreement with those reported elsewhere. A number of relations, e.g. the electron and hole concentrations versus oxygen pressure Po2 and T, as well as the influence of doping (with donors of acceptors) on these relations and on the oxygen content ae predicted using the parameters obtained. The region of high Po2 is also studied.
Relativistic Wave U‐Equation of the Internal Q‐State of the Θ‐(Cu) Superconductor
Authors: Gangan N. A. 
Published: July 2007

AbstractThe coherent (“condensate”) pairing of “Kaino” electrons (those braced by the “nuclei”) in the “perovskite” Θ‐(Cu) superconductor (YBa)CuO3‐θ (θ small) is considered. The invariant definition of the physical S matrix and of the geodesic (on 𝔐) projective variables of the (“inertial”) relative (in the Cayley‐Beltrami metric) three‐variable movement of particles is given. The (Beltrami) W‐invariant (relativistic) three‐dimensional wave equation of the internal (“relative motion”) condensate Q‐state of the Theta;‐(Cu) superconductor is obtained.
Isochoric Thermal Conductivity and Thermal Pressure of Solid CCI4
Authors: Konstantinov V. A. , Manzhelii V. G. , Smirnov S. A. 
Published: July 2007

AbstractIsochoric thermal conductivity and thermal pressure are studied of monoclinic and rhombohedral phases of solid CCl4 at different densities in the temperature range 210 to 300 K and up to the pressures of 200 MPa. It is found that at constant density the thermal conductivity increases with increasing temperature in both the phases. The experimental results are discussed on the basis of the conception of the minimum value of the thermal conductivity.
Antiferromagnetism and Anisotropic High‐Temperature Superconductivity A Further Macroscopic Study
Authors: Shehata L. N. 
Published: July 2007

AbstractThe macroscopic studies of the possible coexistence of antiferromagnetism (AF) with anisotropic high‐temperature superconductivity (SC) are reviewed. A modified Ginzburg‐Landau energy functional is presented. The temperature condition for such coexistence is estimated in terms of the GL coefficients for the uniform SC and AF. The derived equations with the appropriate boundary conditions are used to study the vortex structure and evaluate the first and second critical fields in the new materials. Applications and comparison with the available data are also presented.
A Theoretical Investigation about the “F” Centre in MeF2:A+ (MeCa, Sr; ALi, Na, K)
Authors: Amara A. , Cremer G. , Martin‐Brunetiere F. , Thuau M. 
Published: July 2007

AbstractOne of the most conspicuous colour centres in MeF2:A+ (Me=Ca, Sr; A=Li, Na, K) is the so‐called “Fe”. It is investigated whether this centre may really be composed of three neighbouring fluorine vacancies, along a [0, 0, 1] direction, decorated by two electrons, with an alkaline impurity A+ in the vicinity. This structure seems to be ruled out by a comparison of the experimental magnetic circular dichroǐsm data of other authors with the results of present Hartree‐Fock calculations of the energy levels of linear F centres in fluorite‐like lattices. For this calculation, an H hydrogen molecular ion model is used similar to the ones which have already proved efficient in several other colour centre problems.
Vibrational Spectroscopy of the Structural Phase Transition and Raman Evidence of Librational Fluctuations in Thallium Thiocyanate
Authors: Sathaiah S. , Bist H. D. 
Published: July 2007

AbstractA detailed analysis of Raman and IR spectra of thallium thiocyanate (TINCS) in the temperature (T) range 293 to 438 K is carried out. The orthorhombic‐to‐tetragonal structural phase transition (SPT) near T ≈ 367 K (= Tc) is spectroscopically characterized as an order‐disorder transition exhibiting predominant second‐order features. Remarkably, consistent mean field type exponents:order parameter exponent β = 0.45 ± 0.04 and correlation length exponent v = 0.46 ± 0.04, and activation energy for the reorientational motion of NCS− ions U = (0.32 ± 0.02) eV, are extracted from characteristic spectral changes in the thermosensitive Raman modes. The appearance of side bands in each of the internal modes of the NCS− group in the Raman spectra are attributed to splittings due to an internal field in the ordered orthorhombic phase; the continuous growth in the relative intensities and decrease in splitting energies reveal the gradual diminution of the internal field as T approaches Tc.
Non‐Linear Elastic Behaviour and Third‐Order Elastic Constants of a Roller‐Bearing Steel and Some Standard Steels
Authors: Wasserbäch W. 
Published: July 2007

AbstractThe deviations from Hooke's law in the hardened roller bearing steel SAE 52100 (100Cr6) in cyclic stress—strain experiments are related to the third‐order elastic constants of standard steels and α‐iron. The comparison of the measured values of the non‐linear constant kM, with the values calculated from the third‐order elastic constants reveals a surprisingly good agreement, even for the case that kM, is calculated using the single‐crystal data of α‐iron.
On the Theory of Coupled Phonon—Plasmon Polariton Excitation on the Surface of Polar Semiconductors
Authors: Arakelian V. H. , Hovsepian N. M. 
Published: July 2007

AbstractThe problem of polariton formation on the surface of polar semiconductors is considered. Polaritons are excited by charged particles crossing the interface between vacuum and polar semiconductor. The part of particle energy expended on excitation of coupled phonon‐plasmon polaritons on the interface is calculated. Excitation frequency zones and intensities are found, as well as the loss‐energy dependence on the phase velocity of surface polaritons.
Interpolation of the One‐Electron Energies Using Theoretical‐Numerical Nets
Authors: Kanalin A. G. , Mokhracheva L. P. 
Published: July 2007

AbstractThe method of global Fourier‐series approximation of the one‐electron energies ϵ(k) in the Brillouin zone is considered. To calculate the Fourier series expansions of the ϵ(k)‐functions optimal for trigonometric polynomials theoretical‐numerical nets are used. Convergence and accuracy of the approximation is investigated using one‐ and two‐band models of the ϵ(k)‐dependence. It is shown that the method described is more accurate then piecewise linear interpolation in the volumes of elementary tetrahedra, generated in regular nets, and is comparable to piecewise quadratic interpolation.
Magnetic Field Dependence of Hydrogen Energy Levels in GaAsGa1−xAlxAs Quantum‐Well Structure
Authors: Shen Zhong‐Jun , Zhong Shu‐Au , Gu Shi‐Hei 
Published: July 2007

AbstractA calculation is made of the binding energies of the hydrogenic donor ground state in a GaAsGa1−xAlxAs quantum well of finite barrier height in the presence of a magnetic field, which is taken to be parallel to the growth axis of the quantum‐well structure. Strong‐pertubation theory and pertubative‐variational approach are used. The results are given as a function of the size of the quantum well.
Dissipative Processes Due to Fluxoid Motion in Superconductive YBCO Specimens
Authors: Abbattista F. , Appino C. , Masoero A. , Mazzetti P. , Stepanescu A. , Vallino M. 
Published: July 2007

AbstractComparative measurements are made on the dissipative effects due to dc current flow and ac magnetization processes on the same YBCO superconducting specimen at 77.3 K. The material is brought into the Abrikosov mixed phase by a dc magnetic field H0. Different sets of data are reported concerning: (a) the dependence of the dc resistivity ϱ on H0 and on the current density J, (b) the dependence of H(t) on the frequency and on the value of H0 of the magnetic power loss generated by a very small (0.34 A/m) sinusoidal magnetic field H(t) superimposed to H0. By a numerical calculation it is shown that at high frequencies the magnetic power loss is very closely equal to the one expected for eddy current dissipation in a conducting material whose resistivity depends on the current density and has a value rather closely equal to the one measured on the YBCO specimen with a conventional four‐terminal technique. A second component of the magnetization power loss, which is closely proportional to the magnetization frequency and corresponds to the hysteretic loss, is also seen.
Magnetic Phase Diagram of (Ni1−xMgx)O Solid Solutions
Authors: Menshikov A. Z. , Dorofeev Yu. A. , Klimenko A. G. , Mironova N. A. 
Published: July 2007

AbstractA magnetic phase diagram of the (Ni1−xMgx)O solid solutions is drawn by the results of elastic magnetic neutron scattering and magnetic measurements. The ranges of homogeneous antiferromagnetism (0 ≦ x ≦0.37), tricritical behaviour or frustrated antiferromagnetism (0.37 < x ≦ 0.6), cluster spin glass (0.6 < x ≦ 0.75) and paramagnetic behaviour of the Ni2+ spin moments in the ground state (x ≧ 0.8) are determined. It is shown that diamagnetic Mg2+ ions serve as a source of a random field inducing an extra diamagnetic moment of value 0.35μB.