bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of the Size Quantization on the Cyclotron Effective Mass and the Density of States in Bi Films
Authors: Zaluzny M. 
Published: July 2007

AbstractThe influence of the size quantization on the cyclotron effective mass and the density of states at the Fermi level in Bi films with normal along the trigonal axis is discussed. Calculations are performed in the framework of the Cohen non‐ellipsoidal non‐parabolic model. A comparison with the results obtained in the framework of the ellipsoidal non‐parabolic model is given. A critical discussion of the results reported by Mustafaev and Shakhtakhtinskii is also given.
Interpretation of the Group‐Theoretically Unexpected Shape of the Contour Appearing in the Experimental LCW Data for Si and Ge
Authors: Aourag H. , Khelifa B. , Belaidi A. , Kobayasi T. 
Published: July 2007

AbstractThe discrepancies between the measured and the calculated LCW folding distribution in silicon and germanium are discussed on the basis of symmetry considerations.
Charge Ordering of Multielectronic Clusters in Mixed‐Valence Molecular Crystals
Authors: Klokishner S. I. , Koryachenko A. V. , Tsukerblat B. S. 
Published: July 2007

AbstractMixed valence molecular crystals consisting of multielectronic clusters of transition metal ions of the type of d2–d3 are considered. A theory of charge ordering in these crystals is developed. The conditions for the occurence of one, two, or three phase transitions are eludicated. The peculiarities of the temperature behaviour of the magnetic moment are investigated.
Determination of the Effective Absorption Cross‐Section of F‐Centres in KBr—In by Photostimulated Luminescence
Authors: Kalniņš A. , Pļaviņa I. , Popov A. I. , Tāle A. 
Published: July 2007

AbstractUsing photostimulated luminescence of F, In2+ defect pairs in KBr‐In are proposed to be a very sensitive method for the determination of the effective absorption cross‐section of F‐centres. It is shown that the effective absorption cross‐section of F‐centres equals to 2.0 × 10−16 cm2. Some criteria for the applicability of this method are analysed.
Investigation of the Thermodynamic Properties of Anharmonic Crystals by the Momentum Method. II. Comparison of Calculations with Experiments for Inert Gas Crystals
Authors: Tang Nguyen , Van Hung Vu 
Published: July 2007

AbstractOn the basis of results obtained in a previous paper by the moment method the thermodynamic quantities of the inert gas crystals are calculated. The obtained results are compared with the experimental data and with the ones of other authors.
Size Changes of Lattice Parameters in Ultradisperse Diamond and Silicon
Authors: Gamarnik M. Ya. 
Published: July 2007

AbstractA relative increase of the lattice parameters equal to 2.05 × 10−3 ± 1.8 × 10−4 is established by X‐ray analysis in ultradisperse powder diamond with average size of crystallites equal to 4.6 ± 0.4 nm as compared with the lattice parameter of a large‐crystal sample. The effect found for diamond as well as the experimental data of the increase of the lattice parameters in ultradisperse samples of silicon established previously are explained by the size change of intracrystalline pressure stipulated by the interaction of the excess negative charges arranged on the bond lines CC (or SiSi), and the positive cores of the atoms of the covalent crystal. The size dependences of the relative change of the lattice parameters are calculated in the frameworks of the point model of the charge lattice for diamond and silicon. The dependences show a monotonous increase of the lattice parameters when decreasing the sizes of the crystals. Calculated dependences are in good agreement with experimental data.
Electron and Positron Distributions in Grey Tin
Authors: Aourag H. , Soudini B. , Khelifa B. , Belaidi A. 
Published: July 2007

AbstractElectron and positron charge densities are calculated as a function of position in the unit cell for grey tin,α‐Sn. Wavefunctions are used derived from pseudopotential band structure calculations and the independent particle approximation (IPM), respectively, for the electrons and positrons. Detailed plots of the distributions are along the 〈111〉 (the bond axis). Electron and electron‐positron momentum densities are calculated for (001, 110) plane. The results are used to analyze the positron effect in α‐Sn.
Electronic Structure and Charge State of Oxygen Vacancies in Perfect ZrO2 Crystals
Authors: Sobolev A. B. , Varaksin A. N. , Keda O. A. , Khaimenov A. P. 
Published: July 2007

AbstractCalculations are given for clusters, modeling the electronic structure of the oxygen vacancies in ZrO2 crystals by means of the self‐consistent scattered waves method. The crystalline cluster model is used for the description of the properties of a perfect crystal, while the properties of a defect are described by the embedded cluster model. Forming of vacancies in a ZrO2 perfect crystal is shown to result in trapping of one or two electrons on a vacancy and forming of F+‐ and F‐centers with local states in the perfect crystal energy gap. The characteristics obtained of the electronic structure of F+‐ and F‐centers are in satisfactory accord with the known experimental data.
Two‐Dimensional Character of Electron Gas in Layered InSe Crystals
Authors: Dmitriev A. I. , Kovalyuk Z. D. , Lazorenko V. I. , Lashkarev G. V. 
Published: July 2007

AbstractAn analysis of investigation results of kinetic, galvanomagnetic, and quantum oscillation properties in the range of 4.3 to 300 K permits to construct a phenomenological spatial energy model of the spectrum of the layered semiconductor InSe, pure and intercalated by metal atoms. The dynamics of the temperature variations of the character of kinetic phenomena is suggested. The model suggested serves to prove in experiment and to explain the two‐dimensional character of the current carrier gas in the range of low temperatures as well as the peculiarities of the temperature dependence of transversal and longitudinal specific resistance, magnetoresistance, oscillation, and resonance phenomena in the range of 4.3 to 300 K. An analogy is drawn between the band structure of a single crystal of the layered semiconductors InSe and semiconductor superlattices.
Model Calculation of the Dislocation Resistivity for Copper
Authors: Diallo A. O. Donghol , Mrosan E. , Ziesche P. 
Published: July 2007

AbstractStarting from a cylindrically symmetric scattering potential as a model for the dislocation core and the strain field in the vicinity of the core the specific dislocation resistivity for copper is calculated within the free electron model. Several model potentials are considered. The results are compared with experimental values.
Temperature Dependence of the EPR Spectra of GdBa2Cu3O7−δ Compounds in Orthorhombic and Tetragonal Phases
Authors: Guskos N. , Triberis G. P. , Calamiotou M. , Trikalinos Ch. , Koufoudakis A. , Mitros C. , Gamari‐Seale H. , Niarchos D. 
Published: July 2007

AbstractEPR measurements are presented for two samples of GdBa2Cu3O7−δ of which one is superconducting (orthorhombic phase) and one is nonsuperconducting (tetragonal phase). For the superconducting sample signal associated with Cu2+ and Gd3+ ions are detected above and below Tc (with gGd = 1.999 (2)). The sample with oxygen deficiency gives an EPR signal with a strong temperature dependence up to 30 K coming from Gd3+ ions in GdBa2Cu3O7−δ, with g = 2.063 (3). These characteristics can be ascribed to the semiconducting properties of the tetragonal phase of GdBa2Cu3O7−δ. Below T = 30 K, the sample with tetragonal structure gives an additional EPR line associated with Cu2+ ‐Cu2+ ion pairs. The intensity of the EPR signal strongly depends on the temperature.
Effect of Magnetic Phase Transition on the Electronic Specific Heat Coefficient of Lu(Co1−xAlx)2
Authors: Wada H. , Inoue T. , Hada M. , Shiga M. , Nakamura Y. 
Published: July 2007

AbstractThe low temperature specific heat of Lu (Co1−xAlx)2 is measured between 1.4 and 6.5 K. The electronic specific heat coefficient, γ, is enhanced around the critical concentration for the onset of ferromagnetism, while it is sharply reduced in a ferromagnetic region with a substantial moment. The results are discussed in relation with the magnetism in this system.
Energy Band Structure and Optical Properties of Wurtzite‐Structure Silicon Carbide Crystals
Authors: Gavrilenko V. I. , Postnikov A. V. , Klyui N. I. , Litovchenko V. G. 
Published: July 2007

AbstractThe electroreflection spectra of hexagonal polytypes of SiC, 4H and 6H are measured in the range 1.0 to 5.6 eV. The energies of direct optical transitions are determined using a multiple oscillator model. The electronic band structures of three hexagonal polytypes of SiC (2H, 4H, and 6H) are calculated by the first‐principles self‐consistent linear muffin‐tin orbital (LMTO ASA) method. One‐electron energies and densities of states are obtained in the range ± 15 eV around the top of valence band. The results calculated are compared with experimental data measured in this work and those available in the literature.
Phonon Structure of Raman Scattering Spectra of LiH Crystals
Authors: Tyutyunnik V. I. , Tyutyunnik O. I. 
Published: July 2007

AbstractRaman scattering of light in cubic 7LiH and 6LiH crystals at excitation in the range from 514 to 250 nm is investigated experimentally. Raman spectra of pure crystals are measured at 300 K. For the first time, Raman scattering is found to consist of two components. These components are (1) resonant Raman scattering and (2) nonresonant Raman scattering. Resonant Raman spectrum is obtained and identified as the density of states function of V ‐type defect, whereas the nonresonant Raman spectrum is obtained and identified as the two‐phonon spectrum of LiH. Interesting behaviour of this two‐phonon spectrum is found and used as a basis of the original assignment method. Comparison with data from lattice‐dynamics calculations gives very close agreement and identifies the modes as originating essentially from X, W, and K points at the Brillouin‐zone edges.
Non‐Local Elastic Interaction Energy between a Screw Dislocation and a Point Defect
Authors: Wang R. , Pan K. L. 
Published: July 2007

AbstractThe elastic interaction energy between a screw dislocation and a point defect is given in non‐local elasticity. The interaction energy has no classical singularity. The results show that the interaction energy obtained by classical elasticity is much greater (1.4 eV or so) than the experimental value. However the value obtained by non‐local elasticity is in very good agreement with the experimental value (0.5 eV). It is also proved that the nonlocal interaction energy is lower when in body‐centred cubiciron an interstitial carbon atom locates in the octahedral positions than in the tetrahedral positions.
Slow Relaxation of Bose Qusiparticless on Multilevel Systems
Authors: Safonov V. L. , Farzetdinova R. M. 
Published: July 2007

AbstractA complete microscopic theory is developed for the slow linear and nonlinear relaxation of Bose‐quasiparticles on multilevel equidistant quantum systems in solids. The expressions obtained have general forms and can be used for the determination of the relaxation of the relaxation rate for magnons, phonons, and other elementary excitations in crystals, which contain impurities and defects with an internal structure. It is shown that a process of slow relaxation can influence the spin‐lattice relaxation rate of the nuclear spins of host atoms.
Vacancies and Precipitates in Al–1.9 at% Cu Studied by Positrons
Authors: Gläser U. H. , Dlubek G. , Krause R. 
Published: July 2007

AbstractExperimental and theoretical investigations of positron trapping by disk shaped Guinier‐Preston zones as appearing in AlCu alloys are performed. Using positron lifetime and angular correlation S‐parameter measurements the decomposition phenomena are studied in an Al–1.9 at% Cu alloy. The energy and the wave function of a positron within a cylindrical shaped trap is calculated using Ritz's variational principle. Although a weak localization of the positrons by multilayer Guinier‐Preston zones (GP zones) is to be expected from theory, the experimental spectra are dominated by positron annihilation in vacancies surrounded by Cu atoms. Above 200 °C positron trapping by semicoherent and incoherent precipitates is found.
The Investigation of the Ferroelectric Phase Transition in Cluster Systems of Order‐Disorder Type III. Free Energy
Authors: Yukhnovskii I. R. , Korynevskii N. A. 
Published: July 2007

AbstractThe critical part of the free energy of ferroelectric clusters with dipole–dipole interactions between the particies is obtained. The calculation of physically different contributions to the total free energy is performed. The recursion relations for the coefficients of block Hamiltonians are solved in several approximations. The suitability is examined of each approximation to the appropriate type of critical behaviour of the system. The values of critical exponents of correlation length and heat capacity are calculated.
Impurity Centres in ZnTe Crystals Doped with Be, Mg, Cd, and Hg
Authors: Tsurkan A. E. , Rebrov S. A. , Medvetskii S. P. , Nazarenko L. A. , Shemyakova T. D. 
Published: July 2007

AbstractThe reflection coefficient, Raman scattering, and photoluminescence spectra are investigated in ZnTe crystals, doped by isoelectronic impurities (Be, Mg, Cd, and Hg) up to concentration ≈ 1020 cm−3. It is shown that the above‐mentioned impurities essentially influence the optical and emission properties of ZnTe crystals. It is possible only in that case when the introduced impurity forms a bound exciton complex with the local centre. The bound exciton energies of doped ZnTe crystals are determined.
Positron Radiation at Resonance Dechanneling in Superlattices
Authors: Rudko V. N. 
Published: July 2007

AbstractRadiation of positrons at resonance dechanneling in strained‐layer superlattices is investigated in the case when the wavelength of transverse particle oscillations in the channel is equal to the period of the superlatticeL. It is shown that for various values of the ratio,v, of the first layer thickness toL/2 (another layer thicknesses being constant) the angular dependence of channeling radiation changes from the symmetrical (atv= 1/2) to the strongly asymmetrical one (atv≈ 0 andv≈ 1). Positron radiation in superlattices with strong modulation of the average charges in neighboured superlattice layers is also investigated in the case when the wavelength of transverse particle oscillations is twice as much as the superlattice period. Depending onvthe angular dependence of channeling radiation is changed from the symmetrical one with a single maximum to various two‐maxima dependences.
Optical Absorption by Small Polarons in Palladium Hydride
Authors: Lupu D. , Chirtoc M. , Dadarlat D. , Candea R. M. , Bratu I. , Mecea V. 
Published: July 2007

AbstractThe optical transition of the polaron in Pd‐hydride is evidenced by both, classical and photopyroelectric spectroscopy. The results obtained from comparative studies on PdH0.65 and PdD0.65 are in agreement with the small polaron theory. The photopyroelectric spectroscopy reveals one of the main characteristics of the optical transition of the polaron: maximum phonon emission at the peak frequency.
Calculation of Relaxation Spectrum Function Based on the Quantum Void Model in the Amorphous Alloy Fe40Ni40B20
Authors: Phillips A. H. , Gobran N. K. , Kamel R. 
Published: July 2007

AbstractThe relaxation spectrum function is computed for a model representing a block of atoms forming a metallic glass involving void quanta. This is done by simulating the previously proposed atomic tilting model. By using the Monte‐Carlo method, the atomic positions in the considered block are located. The force of interaction among the atoms is computed by using the Lenard‐Jones potential function for short range order of random close packing. In terms of deduced relaxation spectrum function, the internal friction, Q−1, is calculated. Previously obtained results of Q−1 and the corresponding calculated ones are in good agreement showing the same deviation from the symmetric Debye relaxation spectrum. From a knowledge of the characteristic constants of the distribution function, together with the activation energy of formation of void quanta, the value of the free volume may be determined at any temperature. As a confirmation the amorphous‐crystalline transition temperature at which the void volume became equal to the vacancy volume is calculated and found concordant.
Tensile and Compressive Effect of Intracrystalline Pressure in Small Particles
Authors: Gamarnik M. Ya. 
Published: July 2007

AbstractIt is shown that the volume forces of electrostatic interaction of the crystal lattice elements — ions and electrons — result in intracrystalline pressure (IP) which depends on the size of particles and stipulates the size dependence of the unit cell parameters. Analytical expressions are obtained for the IP by the crystal energy and it is shown that the IP can increase or decrease in small particles depending on the crystal structure, i.e. has tensile or compressing action. The results of the theoretical calculations for NaCl and CeO2 give evidence for the compressing effect of IP in small particles of NaCl and for the tensile effect of IP in small particles of CeO2. These results are in good agreements with experimental data of the changes of the unit cell parameters in small particles of NaCl and CeO2.
Collective Plasmon Modes in Semiconductor Superlattice Structures in the Presence of the Effect of Image Charges
Authors: Aharonian K. H. , Sedrakian D. G. 
Published: July 2007

AbstractDispersion relations are presented of non‐retarded collective plasmon modes in superlattice structures with a strong dielectric mismatch between alternating layers in the presence of the effect of image charges (EICH).
Nonequilibrium Carrier Recombination Channels in Uniaxially Stressed Gapless Semiconductors
Authors: Bakhanova E. V. , Strikha M. V. , Vasko F. T. 
Published: July 2007

AbstractNonequilibrium carrier interband recombination channels such as radiative recombination, transitions with optical phonon emission, and Auger recombination are studied in uniaxially compressed gapless semiconductors. Energy ranges for radiative and phonon recombination are determined. The recombination process with phonon emission, the most efficient at low pressures, is dramatically suppressed when the gap becomes wider than the optical phonon energy. Energy threshold dependences are discussed for the cc → cv Auger process (the recombination energy is carried by a free electron) and for the cv → vv process (the energy is carried by a free hole). Temperature and concentration dependences of the recombination rates for these channels are obtained.
Fine Structure of 2p‐Excitons in KI Single Crystals by Two‐Photon Spectroscopy
Authors: Hasuo M. , Nagasawa N. 
Published: July 2007

AbstractThe fine structure of the 2p‐exciton of KI single crystals due to envelope‐hole coupling is investigated by using high resolution two‐photon excitation spectroscopy. The energies of the split‐off 2P1/2, 2P3/2, and 2P5/2 states are (6.1990 ± 0.0014), (6.1898 ± 0.0003), and (6.1947 ± 0.0004)eV, respectively. The relevant spherical parameter μ and the upper limit for the cubic parameter δ are evaluated to be (0.051 ± 0.022) and 0.004, respectively. The fine structure in the LO‐phonon assisted band is also observed. The LO‐phonon energy at Γ point is obtained to be (16.4 ± 0.4) meV.
On the Nature of the Rhenium Effect. Peculiarities of the Band Structure and Elastic Moduli of W‐ and Mo‐Based Alloys
Authors: Gornostyrev Yu. N. , Katsnelson M. I. , Peschanskikh G. V. , Trefilov A. V. 
Published: July 2007

AbstractIn the rigid band approximation the electronic structure of W–Re and Mo–Re alloys is calculated and their band contribution to the elastic moduli Cik. Critical Re concentrations are determined at which electronic topological transitions occur. An analysis of the computational results for Cik is invoked to discuss variations in the degree of “covalency” and “metallicity” of the chemical bonds in rhenium‐doped tungsten. Consideration is given to the role of the elastic anisotropy constant of W–Re and Mo–Re alloys and to its effect on the individual dislocation mobility and plastic properties of these alloys.
Excitons Bound to Defect Complexes in Heavily Doped CdS
Authors: Georgobiani A. N. , Gruzintsev A. N. , Zayats A. V. 
Published: July 2007

AbstractThe fine structure of the luminescence due to bound excitons is found in CdS crystals doped with alkali metals (AM): lithium or sodium 1018 to 1020 cm−3. In the spectral range of the acceptor–exciton complex emission the optical transitions are explained as recombination of excitons bound to the complexes of nearby‐located defects [AMcdCdi] or [AMcdAMi] with different distances between components: 0.2 to 0.6 nm. The Haynes rule yields Eex/Ecompl = 0.14 for such excitons.
Solutions of the One‐Dimensional Non‐Linearised Ginzburg‐Landau Equations for Optional Vector Potentials
Authors: Bläsing J. 
Published: July 2007

AbstractA possibility to solve the one‐dimensional non‐linearised Ginzburg‐Landau equations is presented. The solutions describe the behaviour of the wave function and density of the Cooper pairs between two points in a weak superconductor as a function of the states in the two points. The coupling between the first and second Ginzburg‐Landau equations is attributed to the influence of the current density and the magnetic field on the solution of the first Ginzburg‐Landau equation. The solutions presented allow the description of the influence of optional vector potentials to a supercurrent in the form of the known Josephson‐current equation.
Electrical Resistivity of Compound Forming Alloys
Authors: Mishra A. K. , Sahay B. B. 
Published: July 2007

AbstractThe harmonic model potential is used to explain the anomalous behaviour in the electrical resistivity of LiPb and NaPb on the basis of pseudo‐binary mixture. The computed results for the electrical resistivity of LiPb and NaPb in the whole concentration range indicate that the Ziman‐Faber formula can safely be used for the study of electrical resistivity of such ternary systems.
Dielectric Properties of Mixed Alkali and Silver Halide Crystals
Authors: Sinha P. K. 
Published: July 2007

AbstractThe static and optical dielectric constants are calculated for the entire range of composition in twelve systems of mixed crystals of alkali halides and silver halides with NaCl‐type structure, by adopting the method developed by Kamiyoshi and Nigara (KN). Transverse and longitudinal optical mode frequencies are also evaluated using the Lyddane‐Sachs‐Teller relation. Calculated values of static dielectric constants are found to exhibit a sharp non‐linear dependence on composition near the equi‐molar region in KClKBr, KClRbCl, KBrRbBr, KIRbI, RbClRbBr, and AgClAgBr mixed crystals and a slight non‐linear dependence on composition near the NaBr end in NaCl‐NaBr mixed crystals, which is in agreement with experimental data. The usefulness of dielectric constants and optical mode frequencies is demonstrated by investigating the composition dependence of the Szigeti effective charge parameter.