bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersion and Propagation of Light in Crystals in the Exciton Absorption Region
Authors: Kudykina T. A. 
Published: July 2007

AbstractAnalogues are obtained of Fresnel's formulas for the reflectivity and transmission of light in the exciton absorption range. Boundary conditions for electromagnetic waves in absorbing media obtained in a previous paper and following from them the law of light refraction are used. Calculation of the light propagation in the An = 1‐exciton absorption range in CdS crystals is in good agreement with the experiment.
A New Approach in the Optical Characterization of Amorphous Hydrogenated Silicon–Carbon Alloys
Authors: Amato G. 
Published: July 2007

AbstractAn expression for the imaginary part of the dielectric function for amorphous silicon–carbon alloys is assumed following previous treatments already adopted for other amorphous semiconductors like silicon, germanium, gallium arsenide, and silicon nitride. The real part of the complex dielectric function is obtained using Kramers‐Kronig analysis. The model requires the knowledge of four parameters. Suitable values of these parameters can be obtained by fitting the optical spectra of the samples. The results show that the parameters allow a deep physical insight and are strictly related to the composition of the films and to the preparation methods.
Time Resolved Spectroscopic Investigations of Pure YAIO3and Ti‐Doped YAIO3Crystals
Authors: Chosrovian H. , Rentsch S. , Grummt U.‐W. 
Published: July 2007

AbstractThe difference of optical densityΔD(λ, t)after light pulse excitation for Ti doped and pure YAIO3crystals is measured within 6, and 1000 ps and 10 μs and 10 s. After laser or flashlamp excitation Ti doped YAIO3crystals show a broad light induced transient absorption (LIA) between 350 to 750 nm, which consists of some independent bands. The bands are formed within a few hundreds ps and have about 103to 105times longer lifetimes as the fluorescence of Ti3+ (11 μs). Flashlamp‐spectroscopic investigations in the 10 μs region of both, Ti doped and pure YAIO3crystals show a similar spectral and temporal behaviour of absorption differences. In order to explain the experimental results the model of bound small‐polaron is used.
Scattering and Annihilation of Positrons in Magnetically Ordered Samples
Authors: Szuszkiewicz S. 
Published: July 2007

AbstractMeasurements are made of the angular distributions of annihilation quanta for metallic glass (CoFe)74 (MnMoSiB)26 samples. It is found that if the spins of annihilating particles are antiparallel, the number of two‐quantum annihilation acts with 3d‐like electrons increase at about 7%. The measurements are also performed for the counting rate of coincidences for tH = 0 as a function of B. A change of the counting rate with the change of the direction of the ordering of the sample indicates the change of number of scattered positrons. However the scattering depends on the electron and positron spins.
Energy Spectrum and Phonon Excitation Damping in Many‐Component Amorphous Solids
Authors: Vakarchuk I. A. , Myhal V. M. , Tkachuk V. M. 
Published: July 2007

AbstractPhonon excitations in many‐component amorphous solids are treated using the Green's function method. The equation for the energy spectrum of phonon excitations is obtained. This equation takes into account the hard core in the interatomic interaction potential, the temperature dependence of phonon frequencies, and their damping, caused by phonon scattering on structure fluctuations. Zeroth approximation is considered in a space with arbitrary dimensionality. In this case it coincides with the quasi‐crystalline one. The explicit expressions for the optic and acoustic modes as well as for the longitudinal and transverse velocity of sound are obtained as example in the two‐component case. In the space of arbitrary dimension the asymptotic of damping is studied for the one‐component system in the long‐wave region. Numerical calculations of the “frequency‐wave vector” dependence are performed for some amorphous metals in the quasi‐crystalline approximation.
Effects of Disorder and Electron Correlation in Disordered Systems
Authors: Brezini A. 
Published: July 2007

AbstractA disordered Hubbard model with diagonal disorder is used to examine the electron localization effects associated with both, disorder and electron–electron interaction. Extensive results are reported on the ground state properties and compared with other theories. In particular two regimes are observed: when the electron–electron interaction, U, is greater than the disorder parameter and when it is smaller.
Mean Field Renormalization Group and Path‐Integral Methods for Spin‐One Disordered Ising Model in a Transverse Field
Authors: Yang C. Z. , Song W. J. 
Published: July 2007

AbstractA new approximate scheme which is combined by mean field renormalization group theory (MFRG) with the discretized path‐integral renormalization (DPIR) is employed in the study of the disordered transverse Ising model. The critical properties of random bonds spin‐one Ising systems on a d‐dimensional lattice are calculated with this new approximate scheme.
Raman Scattering in Amorphous Selenium Molecular Structure and Photoinduced Crystallization
Authors: Baganich A. A. , Mikla V. I. , Semak D. G. , Sokolov A. P. , Shebanin A. P. 
Published: July 2007

AbstractRaman scattering measurements are reported for amorphous selenium. It is found that the molecular structure of a‐Se on the scale of medium‐range order differs from the structure of most inorganic glasses. A laser‐induced glass‐crystalline transition is also studied. The experimental results suggest the existence of successive phases in such transition with pronounced threshold behaviour.
Interaction of Cascade‐Generated Nonlinear Elastic Waves with Dislocation Structure Elements in Metals
Authors: Zhukov V. P. , Boldin A. A. 
Published: July 2007

AbstractThe collective action of spherical elastic waves generated in atomic collision cascades under ion bombardment is shown to give rise to a random force similar to white noise in the dislocation glide plane. By way of example, the behaviour of radiation‐produced perfect dislocation loops and dislocation structure segments under the action of this force is investigated. It is found that the loop depth distribution obeys the diffusion equation with a “diffusion coefficient” proportional to the ion current density J while dislocation generation due to Frank‐Read source activation can be described in the framework of first‐order phase transformation theory, with J in the role of temperature.
The Origin of Electrically Active Centers in a Near‐Coincidence Σ9 Grain Boundary in Germanium
Authors: Wang N. , Wilbrandt P. J. , Haasen P. 
Published: July 2007

AbstractThe electronic defect states of a near‐coincidence Σ9 tilt grain boundary (GB) in germanium is characterized by means of deep level transient spectroscopy (DLTS). An energy level at (0.52 ± 0.02) eV below the conduction band of Ge is found for 1 × 1016 m−2 defect states. The structure of this boundary, which contains GB dislocations (b = 1/9 [221] a), is further studied by high resolution electron microscopy (HREM). The dislocations are found to have many jogs (3 × 1016 m−2) which create dangling bonds. This finding may represent experimental evidence that the dangling bonds are at the origin of the electrical activity of the GB in Σ9 bicrystal.
The Electronic Structure of the Copper Oxide Plane within the Green's Functions Projection Method
Authors: Hayn R. , Yu. Yushankhai V. 
Published: July 2007

AbstractThe projection method for two‐time Green functions is used to derive a self‐consistent set of equations for the spectrum of the two‐dimensional Emery model with infinite copper correlation. In the relevant parameter region near the filling n = 1 a charge‐transfer gap is found, but in difference to the Gutzwiller approximation a finite bandwidth occurs at the transition point. The critical Δc = ϵp — ϵd at which the transition to metallic behaviour occurs is found to be approximately Δc = 2t.
Density of States and Wave Function of Excitons Localized by Alloy Potential Fluctuations in Semiconductor Solid Solutions
Authors: Gourdon C. 
Published: July 2007

AbstractUsing a variational wave function for excitons localized by alloy potential fluctuations, the density of localized states, the exciton localization length, and the effective Bohr radius are calculated as a function of the localization energy. Results are shown for the specific case of CdS1—xSex alloys and compared with experimental results and other previous calculations.
Supraleitung — der Weg zu hohen Sprungtemperaturen
Authors: Urland W. , Tietz F. 
Published: July 2007

AbstractMit Hilfe eines früher entwickelten „Phasendiagramms”︁ zum Verständnis von Supraleitung wird der Weg zu supraleitenden Oxocupraten mit hohen Sprungtemperaturen aufgezeigt.
Lowering of Dimensionality in Phase Transitions with Correlated and Uncorrelated Random‐Exchange or Random‐Field Ising Systems
Authors: Silva P. R. 
Published: July 2007

AbstractThe excess of free energy in the phase transitions of Ising systems is calculated due to the presence of quenched impurities which could generate random exchanges or random fields. Dimensionality reduction is detected in the obtained hyperscaling relation both, in the case of correlated and uncorrelated random‐exchange or random‐field Ising models.
The Magnon Excitations and Magnetic Properties of Quasi‐One‐Dimensional Organic Polymer Ferromagnets
Authors: Su Gang , Xue De‐Sheng , Li Fa‐Shen , Ge Mo‐Lin 
Published: July 2007

AbstractThe magnon excitations and magnetic properties of a theoretical model proposed for quasi one dimensional organic polymer ferromagnets are investigated. It is found that two non‐degenerate magnons exist in the system, and their excitations are analog with those ones in ferrites. The specific heat, magnetization, and zero‐field susceptibility of the system are also obtained, and found that the model shows some exotic behaviors.
(TMTSF)2(2,5‐DBr‐DCNQI) — A Novel Kind of CT‐Complex Electrical and Magnetic Properties Originating from Different Stacks
Authors: Söderholm S. , Von Schütz J. U. , Schaumburg G. , Helberg H. W. , Erk P. , Hünig S. 
Published: July 2007

AbstractElectric and magnetic properties of the new charge‐transfer complex (TMTSF)2(2,5‐DBr‐DCNQI) are reported. The microwave conductivity is thermally activated with an activation energy of 10 meV, and the room temperature conductivity is 10−1 to 10−2 Ω−1 cm−1. The charge transport is due to hopping between TMTSF sites. The real part of the dielectric constant is unexpectedly large, 200 at 300 K, and shows a weak temperature dependence. The presence of localized charge carriers can explain the magnitude of the dielectric constant. The spin systems associated with the TMTSF and DCNQI molecules, respectively, are strongly coupled. The dominating contribution to the ESR linewidth, above 130 K, is spin‐orbit coupling. The temperature dependence of the linewidth is due to electron phonon interaction and the hopping of the charge carriers. The susceptibility is high, 8 × 10−4 e.m.u./mol at 300 K, and is dominated by the contribution from the spins associated with the DCNQI molecules. The temperature dependence is the one of an antiferromagnetically coupled one‐dimensional Heisenberg chain with an exchange interaction of about 6 K.
Photoluminescence of RbPb2Cl5
Authors: Nikl M. , Nitsch K. , Polak K. 
Published: July 2007

AbstractEmission and absorption properties of RbPb2Cl5 crystals are reported for the first time at the temperature 4.2 to 300 K. The lowest energy absorption peak at 275 nm is ascribed to a cationic exciton at Pb2+ site analogically to PbCl2. Two emission bands are found peaking at 340 and 510 nm under excitation in the exciton absorption region. They are ascribed to radiative decay of the cationic exciton at two different minima of excited APES at the Pb2+ ion. A comparison of RbPb2Cl5 emission properties with those of PbCl2 and RbCl:Pb is made.
Compton Scattering Studies in ZnS and ZnSe
Authors: Panda B. K. , Padhi H. C. 
Published: July 2007

Abstract59.54 keV γ‐ray Compton profiles (CP) of polycrystalline samples of ZnS and ZnSe are reported for the first time. Both the profiles scaled to lattice momentum are found to be similar except for the low momentum region where ZnS profile is more peaked. The difference in the two profiles at the low momentum region could be a core‐orthogonalisation effect which needs to be evaluated.
Strain‐Induced Magneto‐Optical Anisotropy in Semimagnetic Quantum‐Well Structures
Authors: Goede O. , Heimbrodt W. , Köpp Th. , Gumlich H.‐E. , Lunn B. , Ashenford D. E. 
Published: July 2007

AbstractIt is shown that the lattice‐misfit induced biaxial strain in quantum‐well structures with semimagnetic barriers leads to a significant anisotropy of the shift and splitting of the subvalence bands in the barriers by an applied magnetic field. The calculated barrier exciton energies in dependence of a magnetic field parallel or perpendicular to the sample axis are confirmed by the measured anisotropic shift of the luminescence and reflection peaks for various CdTe/(Cd, Mn)Te quantum‐well structures grown by MBE on InSb substrates. Consequences on the behaviour of the well excitons in a magnetic field are discussed.
Diffusion Constants for the Vacancy Mechanism in Mg and α‐Zr Calculation
Authors: Monti A. M. 
Published: July 2007

AbstractSelf‐diffusion coefficients for the monovacancy mechanism described in terms of the Arrhenius law are calculated in Mg and α‐Zr from computer simulation results. Different short‐range pair interatomic potentials which reproduce some material properties are used. Special interest is devoted to the results obtained for the α‐Zr lattice; by assuming a vacancy‐formation energy value Ef = 1.8 eV, a self‐diffusion energy value Q = 3.3 eV and a pre‐exponential factor D0 = 5 × 10−5 m2 s−1 are obtained. These numbers indirectly support some ideas proposed in the literature to understand the self‐diffusion behaviour shown by experimental results, as well as some predictions made by other authors.
Tight‐Binding Approach to the Dangling Bond Feature of Covalent Crystals
Authors: Uemura Y. 
Published: July 2007

AbstractA potential function is proposed which is responsible for dangling bond generation in defect structures of covalent crystals. The defect energy is calculated by the tight‐binding method using this potential. All atoms in the defect region are relaxed in six degrees of freedom (three translations and three rotations of a tetrahedron considered at each atomic site). This method is applied to a (111) twist boundary for calculating the boundary energy and the structure. The boundary energy seems mainly to be governed by the dangling bond density which is determined by dividing the number of dangling bonds by the number of atoms included in a supercell at the interface. But in the low energy region, the dependence between them is not so simple. In the case of a low dangling bond density, the relationship between the boundary energy and the rotation angle resembles the result reported for the twist boundary in ionic crystals.
Computer Modelling of the Dynamics of Space Dislocation Ensembles II. Flexible Dislocations. After‐Effect Stages
Authors: Volyntsev A. B. 
Published: July 2007

AbstractThe dislocation mechanisms of spontaneous plastic flow of deformed solids after their unloading, that is the dislocation reverse mechanical after‐effect (RMA), is considered. A previous model is developed with account of dislocation flexibility and the possibility to conduct a computing experiment in the mode of preliminary loading with a fixed velocity of deformation. The evolution of structure and the RMA temperature dependence in the course of continuous heating of deformed materials is analyzed.
Fractal Analysis of Optical Domain boundaries in Y1Ba2Cu3O7−δ Single Crystals
Authors: Müller J.‐P. , Schurig Th. 
Published: July 2007

AbstractOptical domains on YBaCuO single crystals can be observed under polarized light. These domains are distinguished by different orientations of twins. The arising domain boundaries have a stepped shape and can be regarded as self‐similar in a limited range of magnification. By using different methods it is possible to characterize optical domain boundaries by fractal geometry. Fractal dimensions are obtained which are a measure of the boundary roughness.
Electronic Structure of A1BiS2 Semiconducting Compounds
Authors: Soldatov A. V. , Sukhetskii Yu. V. , Lavrentiev A. A. , Gusatinskii A. N. , Gubskii A. L. 
Published: July 2007

AbstractSulphur X‐ray fluorescent K bands, X‐ray absorption near the edge structure (K‐XANES), and emission L2,3 bands are obtained in semiconducting A1BiS2 (A1 = Li, Na, K, Rb) sulphides. The electronic structure of the [BiS6]9− cluster, which is a fragment of the investigated compounds, is calculated by the self‐consistent field Xα‐scattered wave (Xα‐SW) method. On the basis of a joint analysis of X‐ray emission spectra the fine structure, the XANES data and the results of Xα‐SW calculation the energy band structure and the character of chemical bond in A1BiS2 type compounds is investigated. The origin of the anomalous increase of the energy gap in these compounds is established when the atomic number of alkaline metal increases.
On a Concept of Quasiparticles with Parastatistics
Authors: Safonov V. L. 
Published: July 2007

AbstractA possibility of description of some physical models in solids in terms of quasiparticles with parastatistics is considered. These quasiparticles can be introduced both by Green's generalized second quantization and by means of a nonlinear operator transformation for Bose and/or Fermi operators. Several examples of the nonlinear transformations are given. Some physical properties of the superconducting models are discussed.
Theoretical Calculation of Positron Annihilation Angular Correlation Anisotropy in GaP
Authors: Panda B. K. , Mahapatra D. P. , Padhi H. C. 
Published: July 2007

AbstractAngular correlation of positron annihilation radiation along [100] and [111] directions of GaP are calculated using pseudopotential formalism. The positron wave‐function is solved in point core approximation. The calculated 2γ momentum distribution anisotropy agrees reasonably with the experimental data.
Photochemical Reorganization of Deep Impurity Centres in Silicon. Dissociation of Donor–Acceptor Pairs
Authors: Adilov K. A. 
Published: July 2007

AbstractReversible processes are observed of photochemical reorganization of deep centres in p‐type silicon doped with zinc, selenium, and chromium under the illumination of light in the impurity absorption region. The dissociation is found of donor–acceptor pairs (Zn+iB−s, (Se+iB−s)°, and (Cr+iB−s)° followed by isolated centres of Zn+i and Se+s.
Localized States Induced by Self‐Interstitial Defects in Ultra‐Thin GaP/InP Strained‐Layer Superlattices
Authors: Wang En‐Ge , Wang Ding‐Sheng 
Published: July 2007

AbstractBy the recursion method a theoretical study is made of the electronic structure of a (001)‐oriented (GaP)1/(InP)1 strained layer superlattice with interstitial defects. A Keating model is used to determine the structural parameters. The density of states of all possible interstitials and their neighbors in the stable monolayer superlattice are calculated. Some new self and impurity diffusion mechanisms, which are not found in a GaAs/AlAs matched superlattice, are proposed for the first time.
The Charge Distribution and the Electric Field Gradient in the High‐Temperature Superconductor TlBa2Can−1CunO2n+3 (n = 1 to 3)
Authors: Jia Y. Q. 
Published: July 2007

AbstractThe net charges at atoms in the high‐temperature superconductor TlBa2Can−1CunO2n+3 (n = 1 to 3) are calculated by means of the tight‐binding approximation based on the EHMO method. The results indicate that the charge distribution in this kind of compounds possesses a specially layered arrangement. An insulating Ba–Ba layer is inserted between the CuO layer and the TlO layer. There may exist a weak coupling between the CuO layer and the TlO layer through the interaction of the same O(2) atom with both the Cu atom and the Tl atom. The existence of the Ca in the compounds can cause the valence fluctuation at the Cu atom. The calculated electric field gradients at atoms implies that the conducting electron or hole may move in the CuO layer, which is closest to the TlO layer, along the a–b plane.
On the Gilinskii Branch of the Spectrum of Excitations of a Domain Wall in Uniaxial Ferromagnetics
Authors: Shimokhin I. A. 
Published: July 2007

AbstractA high‐frequency branch of the spectrum of excitations of a domain wall in uniaxial ferromagnetics, discovered by Gilinskii, is studied. A dispersion law for all directions of the wave propagation is derived from the Landau‐Lifshitz equation in magnetostatic approximation. Results are obtained in the long wave limit. A comparison of the theoretical and numerical results is presented.
Frequency and Temperature Dependences of Exciton Damping in CdS Crystals
Authors: Ya. Reznichenko V. , Strashnikova M. I. , Cherny V. V. 
Published: July 2007

AbstractDispersion curves of the refractive index and absorption spectra measured on thin wedge‐shaped and plane‐parallel CdS crystals are compared with corresponding dependences calculated on the framework of Pekar's theory. Frequency and temperature dependences of exciton polariton relaxation parameter are determined from the best fit.
Raman Spectra of [N(CH3)4]2ZnCl4 Single Crystals. II. Raman Spectra of Low‐Symmetry Phases
Authors: Torgashev V. I. , Yuzyuk Yu. I. , Rabkin L. M. , Durnev Yu. I. 
Published: July 2007

AbstractPolarized Raman spectra of [N(CH3)4]2ZnCl4 single crystals are studied in five low‐symmetry phases in the frequency range 10 cm−1 < ν < 3500 cm−1. The observed lines are assigned on the basis of a factor‐group analysis and corresponding correlational relationships. The order of the crystal lattice is increased as the temperature is lowered. The phase transition in this compound are of order–disorder type.
Channels of Relaxation of Elastic Stresses in Pentagonal Nanoparticles
Authors: Gryaznov V. G. , Kaprelov A. M. , Romanov A. E. , Polonskii I. A. 
Published: July 2007

AbstractOn the basis of continuous elastic models relaxation channels of elastic stresses inside the pentagonal needle‐like nanoparticles (PNNPs) are considered. Six models are analyzed: 1. creation of a dislocation inside the PNNP; 2. opening of a gap in the PNNP; 3. creation of a disclination bound with the PNNP surface; 4. splitting of the pentagonal axis; 5. growth of monocrystalline region around the PNNP axis; 6. displacement of the pentagonal axis towards the periphery of the PNNP. An energetic balance and the possibility of realization for each of these channels are discussed.
A Correlation Study of Large Potassium Cationic Clusters
Authors: Ray A. K. , Kanal K. M. , Howard I. A. 
Published: July 2007

AbstractFourth‐order many body perturbation theory is used to investigate the properties of large potassium cationic K (8 ≦ n ≦ 13) clusters. Detailed electronic structures of these clusters are studied. Stabilities from the points of view of binding and fragmentation energies are discussed and, wherever possible, results are compared with published data in the literature.
Investigation of Cu and Ni Band Structure above the Vacuum Level Using Low Energy Electron Reflection
Authors: Strokov V. N. , Komolov S. A. 
Published: July 2007

AbstractIncidence angle dependent elastic electron reflection curves in the 0 to 30 eV range are measured on Cu(111) and Ni(111) using target current regime. They are compared with the calculated ones. Computations are made very fast using a simple approximation. The extrema of the reflection energy derivative are shown to correspond unambigiously to definite critical points of bands. These points are mapped when the energies of the experimental extrema are compared with the calculated ones. Varying the incidence angle, in this way bands in the variety of Brillouin zone directions may be investigated.