bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Crystal Electron Energy and Compton Profile Calculations from X‐Ray Diffraction Data
Authors: Aleksandrov Yu. V. , Tsirelson V. G. , Reznik I. M. , Ozerov R. P. 
Published: July 2007

AbstractThe method of the one‐electron density matrix determination from X‐ray diffraction data is developed. It takes into account the translational symmetry and is applicable to covalent crystals. The crystal energies and directed Compton profiles are calculated in impulse approximation for silicon and diamond. The agreement with the experiments is rather good.
The Soliton Generalization of The Bipolaronic Model Proposed for the High‐Tc Superconductivity in Lanthanum and Yttrium Cupric Oxides
Authors: Mańka R. , Molak A. 
Published: July 2007

AbstractA modified bipolaronic model of high‐Tc superconductivity is proposed. The model includes electron‐phonon and antiferromagnetic bipolaron mechanisms. Characteristic property of high‐Tc superconductivity is the lowered dimensionality which is essential for the formation of topological soliton. This model is related to the layered structure of La‐Sr‐Cu‐O and Y‐Ba‐Cu‐O compounds.
Theoretical Study of Density of States and Specific Heat of Itinerant Ferromagnetic Superconductors
Authors: Kakani S. L. , Paliwal R. K. 
Published: July 2007

AbstractDensity of states and specific heat of itinerant ferromagnetic superconductors are studied by using the mean field approximation. The results are applied to the system Y9Co7. There is satisfactory agreement between theory and experimental results.
To Magnetic Solutions of the Hubbard Model
Authors: Lindner U. , Schumacher W. 
Published: July 2007

AbstractFrom the existence of double solutions of the Néel temperature in the Hubbard model for nearest neighbour overlap and simple cubic lattice in the framework of the Hartree‐Fock approximation as well as within the unified theory of Moriya and Hasegawa it follows that it is necessary to conclude further magnetic (commensurable and incommensurable) phases in the magnetic phase diagram. The investigation is restricted to magnetic long‐range order.
The Shape of the Multi‐Plasmon Radiation Band in Direct Gap Semiconductors
Authors: Klyukanov A. A. , Senokosov E. A. , Chibotaru L. E. 
Published: July 2007

AbstractThe form‐functions of the multi‐plasmon light absorption spectra are obtained using the fluctuation‐dissipation theorem. Transitions with photon and plasmon absorption leads to the absorption edge shift into the longwavelength spectrum region obeying Urbach's rule. It is shown, that the ground state exciton interaction with plasmons is weak due to the smallness of the Bohr radius compared to the Debye screening radius. The band shape of the multi‐plasmon own radiation of the nondegenerative electron—hole plasma is calculated. Multiplasmon transitions are direct ones whereas the radiation band consists of the superposition of equidistant Maxwell bands being apart from each other by the plasmon frequency. The amount of the multi‐plasmon satellites depends on the value of the plasma emission constant and plasma temperature. Indirect multiplasmon transitions lead to more abrupt radiation intensity decay at the short wave edge of the band. It is shown that plasmon dispersion leads to the shift of the peak value positions of the single‐plasmon satellites. The theory of multi‐plasmon transitions in semiconductors developed with account of the LO phonon replicas coincides with experimental data.
Reflectance Spectroscopy on Zn1−xMnxS in the Energy Range from 11 to 20 eV by Use of Synchrotron Radiation
Authors: Flach E. , Gumlich H.‐E. , Jung Ch. , Krause M. 
Published: July 2007

AbstractInterband transitions derived from S 3s‐states and core level excitations of Zn 3d‐states are studied in Zn1−xMnxS. The investigations are performed using synchrotron radiation reflection spectroscopy both at T = 115 K and at room temperature. Below the onset of transitions from the Zn 3d‐levels into the conduction band two peaks are found due to the excitation of Zn 3d core level excitons, originating in the spin—orbit splitting of the Zn 3d‐level. The amount of the splitting is 0.23 eV for zincblende structure and 0.55 eV for wurtzite structure. Tentative assignments are given for the higher transitions and the influence of increasing manganese concentration on the shape of the reflectance spectra is discussed.
Simulation of Perfect Vacancy Loops in B.C.C. Metals
Authors: Kapinos V. G. , Osetskii Yu. N. , Platonov P. A. 
Published: July 2007

AbstractStructure parameters and energies are calculated by computer simulation for faulted vacancy loops (VL) on the {110} plane in α‐Fe. The interaction between ions is described by a potential developed within the scope of the local pseudopotential theory. The size of the Frank VL dislocation core is found by comparing simulation results and continuum theory calculation. A structure simulation for small vacancy loops on the {110} plane without stacking faults with Burgers vectors b =〈100〉and b = (1/2)〈111〉 is performed.
Phase Transformation in F.C.C. Thorium and its Theoretical Stability on the Path of Transformation
Authors: Thakur K. P. , Ahmad S. 
Published: July 2007

AbstractTheoretical calculations are carried out to locate the stress‐free b.c.c. phase in f.c.c. thorium on the basis of physical computations of the forces of atomic interactions. Internal energies corresponding to the stress‐free b.c.c. and stress‐free f.c.c. phases and the required stress and energy changes for the f.c.c. → b.c.c. transformation in thorium are presented. Ranges of G and S stability are identified according to the Born stability criterion, by computing the numerical values of the respective elastic moduli on the line of deformation connecting the stress‐free b.c.c. and stress‐free f.c.c. phases of the crystal. The generalised Morse potential model is used to carry out the calculations.
Two‐Component Solitary Excitations in α‐Helical Protein Molecules
Authors: Ichinose S. 
Published: July 2007

AbstractInterspine interaction effects on stationary and thermodynamic properties of α‐helical protein molecules are studied using a perturbation formalism. It is shown from zeroth order condition that intrapeptide vibration Amide I corresponds to a total of three types of solitary excitations. At low temperatures, such solitary excitations are valid for obtaining information about thermodynamic properties of α‐helical protein molecules.
Structural Network and Some Photoelectrical and Optical Parameters of Amorphous Hydrogenated Silicon
Authors: Golikova O. A. , Grekhov A. M. 
Published: July 2007

AbstractThe results of an experimental study of a‐Si: H films are presented: dark and photoconductivity hydrogen concentration and SiH2/SiH ratio, optical gap, and Raman frequency. The deposition temperature is shown to be the main factor of the transformation of the density of localized states and corresponding shifts of the Fermi level. Theoretical calculations are made of the model of SiHSi bonds in the cluster approximation. The results concerning the Fermi level shifts are interpreted on the basis of this model.
Polariton Theory of Light Propagation in Crystals I. Connection between the Microscopic Theory of Exciton—Phonon Polaritons and Maxwell Equations
Authors: Glinskii G. F. , Koinov Z. G. 
Published: July 2007

AbstractThe light propagation in a crystal is considered as a polariton propagating through the crystal assuming no polariton damping. With the use of the Legendre transforms a set of nine independent exact equations is derived for the corresponding vertex and Green's functions. All possible correlation and screening effects are included in principle. Knowledge of the solutions of the above equations provide the excitation energies of the quasi‐particles (polaritons) formed by coupling of excitons with photons and phonons. Examination of the poles of the two‐particle electron—hole Green's function leads to an equation for the Bethe‐Salpeter amplitudes, as well as to the microscopic derivation of the Maxwell equations.
Optical and EXAFS Investigations of ZnS:Tm3+ Powders
Authors: Dexpert‐Ghys J. , Charreire Y. , Esteban‐Puges P. , Albert L. , Dexpert H. 
Published: July 2007

AbstractThe EXAFS (extended X‐ray absorption fine structure) analysis at the thulium LIII edge is applied to ZnS:Tm3+ luminescent powders. EXAFS oscillations are observed only for higher initial dopant concentrations of 1% and are attributed to oxysulfide (TmO)2S. This parasitic phase is not detected in the fluorescence spectra. By site selective excitation the emission spectrum of the same ZnS:Tm3+ (1%) powder is separated into two components. One of them is attributed to substitutional Tm on Zn sites. The nature of the other one could not be established, it is tentatively interpreted as due to a TmO complex.
Plasmons in Randomly Layered Systems
Authors: Zimpel M. , Barnas J. 
Published: July 2007

AbstractCollective electronic excitations (plasmons) in layered structures with randomly distributed thicknesses are analysed theoretically in the classical approximation. The plasmon localization length λ and the density of plasmon states (DOS) are calculated numerically. Self‐averaged results are obtained for structures consisting of 105 to 106 elementary units. The dependence of λ and DOS on the disorder strength is also discussed.
Magnetic Properties of Disordered Ising Ferrimagnets
Authors: Zheng Siming 
Published: July 2007

AbstractThe magnetic properties of disordered Ising ferrimagnets with S = 1/2 and S = 1 are investigated by means of a new simple method. The equations for magnetization and Curie temperatures are obtained as functions of concentration p of S = 1/2 atoms. Calculations for s.c. lattice are carried out and the results discussed.
Diffraction X‐Ray Radiation under Multiwave Diffraction
Authors: Ba Ha Truong , Dubovskaya I. Ya. 
Published: July 2007

AbstractThe general expressions for the spectral‐angular distributions of quasi‐Cherenkov and diffraction radiations from relativistic particles are derived in the multiwave diffraction case. The transition of the expressions obtained to the well‐known formulae is demonstrated in the two‐wave approximation.
Intersubband Raman Scattering in Size‐Quantized Narrow‐Gap Semiconductor Films
Authors: Okulski W. , Załużny M. 
Published: July 2007

AbstractThe problem of the influence of c‐v mixing on the intersubband Raman scattering in size‐quantized narrow‐gap semiconductor films is considered in the framework of the two‐band effective mass approximation. An expression for the scattering cross section is derived in the infinite deep square well model employing the dipole approximation. A comparison with the results obtained in the one‐band effective mass approximation by Genkin and Sokolov is given. The quadrupole correction to the scattering cross section is also dicussed.
Alkali‐Metal‐Intercalated Indium and Gallium Selenides Non‐Monotonous Shift of Exciton Lines
Authors: Lukyanyuk V. K. , Voronyuk S. P. , Kovalyuk Z. D. 
Published: July 2007

AbstractAbsorption spectra are measured in layered semiconductors InSe and GaSe intercalated with lithium and sodium. A non‐monotonous shift is found of the free exciton lines for NaxInSe, NaxGaSe, and LixGaSe when x increases: at specific values of intercalant content the short‐wavelength shift changes into the long‐wavelength one. Interpretation of the results is made in terms of the strain effects of van der Waals and intralayer bondings which shift the electronic levels of the semiconductor.
Extension of the Crystal Chemistry Approach for the Location of Muonium in Crystals
Authors: Souiri M. , Goltzené A. , Schwab C. 
Published: July 2007

AbstractBy introducing a simple screening parameter, former correlation between the hyperfine coupling constant of normal muonium and the difference of cation electronegativity is improved with respect to that of hydrogen. Further crystal chemistry considerations show why small electronegativity values are required for the occurrence of bond‐centred anomalous muonium.
Theoretical Interpretation of EXAFS Results for the Relaxation in Mixed Crystals
Authors: Maiti S. N. , Sengupta S. , Roy D. 
Published: July 2007

AbstractUsing EXAFS technique it is possible to measure the relaxation of the nearest neighbours around a substitutional defect and at a finite concentration one obtains distinctly two types of nearest‐neighbour distances in a binary solid solution. A relation is derived containing a single parameter for the variation of these two types of nearest‐neighbour distances with concentration which predicts the results successfully both, for alkali halide solid solutions and covalently bonded tetrahedral solid solutions of zincblende structure. The parameter is calculated for alkali halide solid solutions using information of the perfect crystals only.
Calculation of Phase Diagrams in the Lattice‐Gas Model by Modified Cluster Field Method Application to High‐Temperature Superconductors
Authors: Zubkus V. E. , Lapinskas S. , Tornau E. E. 
Published: July 2007

AbstractA modified cluster field method is proposed to investigate the phase transition thermodynamics and phase diagrams of systems described by the lattice‐gas model. By comparison with the exactly solved hard hexagon model and the competing interaction model on a triangular lattice the high accuracy of this method is demonstrated. The method proposed is also used to calculate the phase diagram in the high‐Tc superconductor YBa2Cu3O7‐x. The absence of two‐phase regions in this crystal at 0 ≦ x ≦ 1 and superconducting temperatures is shown. A chain mechanism for change of the oxygen content is proposed.
Thermodynamic Properties of Binary Alloy and Lattice Gas in Gaussian Fluctuation Approximation
Authors: Markowski M. , Murakowski J. , Onyszkiewicz Z. 
Published: July 2007

AbstractGaussian fluctuation approximation (GFA) is used to calculate free energy and the equation of state for two models equivalent to the Ising one: binary alloy and lattice gas. The results are compared with the results obtained within the molecular field approximation (MFA). The equations of state are used to draw phase diagrams.
Analysis of Combination Rules for Elastic Constants of Mixed Ionic Crystals
Authors: Shanker J. , Singh R. , Kumar M. 
Published: July 2007

AbstractVarious combination rules, proposed so far, for predicting the elastic constants of mixed ionic crystals are critically examined. The mathematical forms of different combination rules are derived, and the numerical results estimated from them are compared with one another. It is found that although the mathematical forms of the combination rules appear to be different from each other the numerical results obtained from them are closer to each other.
Generalized Formulae of Frequency Dispersion and Raman Scattering Cross‐Section of Phonon‐Polaritons
Authors: Jiang Yi‐Jian , Liao Li‐Ji , Chen Gang , Zhang Peng‐Xiang 
Published: July 2007

AbstractBased upon the work of Born and Huang, the general dispersion relation for long‐wave phononpolaritons of Borstel and Claus is retreated as a result of crystal optics. The dispersion relation is a generalized Fresnel's equation and can be used in monoclinic and triclinic crystals. And a generalized formula of the differential cross‐section of Raman scattering by phonon‐polaritons is derived by way of fluctuation dissipation theory. This formula is applicable to monoclinic and triclinic crystals as well.
Temperature Dependence of Entropies and Specific Heats of Liquid Na and K
Authors: Joarder R. N. , Mujibur Rahman S. M. 
Published: July 2007

AbstractThe temperature dependence is investigated of the entropies and specific heats of liquid Na and K. The systems are primarily modelled with a hard sphere (hs) description, but contributions arising from the soft forces and electronic part are also included with the basic hs model. The hard sphere ingredients at various temperatures are determined through the consideration that the difference between the relevant pair potential and its minimum value is just equal to the kinetic energy of a free particle. The basic ingredients thus obtained are employed to calculate the entropies and specific heats of the systems at various temperatures. The calculated values are found to be in good agreement with experiments.
Surface Electromagnetic Waves in Quasiperiodic Superlattices
Authors: Goliney I. Yu. , Rudko V. N. 
Published: July 2007

AbstractDispersion equations are obtained and the conditions of existence are considered for surface electromagnetic waves in quasiperiodic dielectric superlattices with layers arranged according to the recurrent Fibonacci rule. It is shown that in the quasiperiodic superlattices an immense number of surface modes exists approximately proportional to the number of layers in the structure. Excitation of surface waves is studied in quasiperiodic superlattices using attenuated total reflection (ATR) technique. Angular and frequency dependences of reflection coefficient for ATR technique are of fractal character.
Surface Polarons at the Contact of Two Polar Crystals
Authors: Pokatilov E. P. , Beril S. I. , Fomin V. M. , Riabukhin G. Yu. 
Published: July 2007

AbstractA theory of surface electron states at the contact of two polar media is developed. The electron—phonon Hamiltonian for a contact of two polar layers is given. Ground state and effective mass energies are determined in a weak coupling approximation. Conditions for polaron localization in the contact region are discussed.
Thermo‐Galvanomagnetic Phenomena in Spin Quantum Wells
Authors: Karyagin V. V. , Lyapilin I. I. 
Published: July 2007

AbstractTransport phenomena in spin quantum wells (SQW) are studied based on narrow‐gap magnetically mixed semiconductors. In contrast to compositional quantum wells, the depth of SQW is easily changed under the action of temperature or magnetic field, which leads to a change in the concentration of quasi‐two‐dimensional electrons in SQW. It is shown that in this case the coefficients of transverse magnetoresistance and thermoelectric power display non‐monotonic dependence on temperature and magnetic field.
Simple Analysis of Atomic Forces Acting on Silicon Surfaces
Authors: Tomášek M. , Pick Š. , Gadiyak G. V. , Morokov Yu. N. 
Published: July 2007

AbstractExtensive recursion method calculations of silicon (001), (111) and (111) surfaces, both ideal and with adatoms and steps, are analyzed and a simple, transparent picture of the origin of forces acting between surface atoms is arrived at. The results fall into three distince groups depending on the character of surface states near EF. Within each of these groups, the interactions have a pair‐wise character. The interpretation is made using the generalized Hückel rule and low order moments of the Hamiltonian. The comparison with ab initio calculations is much improved when direct interactions between surface nearest neighbours are included. The relation of the conclusions to recent empirical approaches is shortly mentioned.
Theory of Surface Polariton Excitation by Charged Particles in a Layer with Account of Retardation
Authors: Arakelian V. H. , Bagdassarian L. A. 
Published: July 2007

AbstractSurface electromagnetic waves or surface polariton (SP) excitations are considered in material layer by means of moving charged particles. A general theory of the problem is given (including retardation) without any limitations for its parameters. Compact expressions for the energy spectrum of the two possible SP branches are obtained, as well as a number of calculation curves for surface phonon‐polaritons and surface plasmons. Certain particular cases of the problem are considered. SP excitation with high phase velocities is treated in detail. SP are shown to be intensively excited only at those frequencies for which ‐1 ⪅ ε (ω) < 0.
One‐Particle Excitation Spectrum in a Bisoliton Model of Superconductivity
Authors: Ermakov V. N. , Kruchinin S. P. 
Published: July 2007

AbstractA bisoliton model of high‐temperature superconductivity is formulated in terms of one‐particle states. The transition to a superconducting state is shown to be accompanied by the energy spectrum rearrangement. The dielectric gap typical for BCS theory is appeared. Its dependence on concentration of carriers is of nonmonotonous character. The conditions for realization of a bisoliton mechanism of superconductivity are considered.
One‐ and Two‐Dimensional Sublattices as Preconditions for High‐Tc Superconductivity
Authors: Krüger E. 
Published: July 2007

AbstractIn an earlier paper it was proposed describing superconductivity in the framework of a nonadiabatic Heisenberg model in order to interprete the outstanding symmetry properties of the (spin‐dependent) Wannier functions in the conduction bands of superconductors. This new group‐theoretical model suggests that Cooper pair formation can only be mediated by boson excitations carrying crystal‐spin‐angular momentum. While in the three‐dimensionally isotropic lattices of the standard superconductors phonons are able to transport crystal‐spin‐angular momentum, this is not true for phonons propagating through the one‐ or two‐dimensional CuO sublattices of the high‐Tc compounds. Therefore, if such an anisotropic material is superconducting, it is necessarily higher‐energetic excitations (of well‐defined symmetry) which mediate pair formation. This fact is proposed being responsible for the high transition temperatures of these compounds.
On the Microscopic Theory of Optical Properties of Crystals with Incommensurate Phases
Authors: Shvaika A. M. , Mokhnyak S. M. , Stasyuk I. V. 
Published: July 2007

AbstractThe microscopic description and symmetry analysis of the refracting properties for incommensurate phases of dielectric crystals are performed. The contributions conditioned by anharmonicities and nonlinear electron polarizabilities are distinguished. It is shown, that the symmetry of tensors describing refracting properties is not changed at the commensurate—incommensurate phase transition.
The Gauge Theory of Point Defects
Authors: Grachev A. V. , Nesterov A. I. , Ovchinnikov S. G. 
Published: July 2007

AbstractClassification of affine‐metric space theories can form the basis for geometric classification of defects. A GL(3, R) ⊳ T(3) gauge theory of linear and point defects is constructed. An asymptotic behaviour for spherical point defect is obtained by solution of fiels equations.
The Effect of a Third Component Impurity C on the Heat Capacity of A3B‐Type Ordered Alloys
Authors: Mekhrabov A. O. , Babaev Z. M. , Matysina Z. A. 
Published: July 2007

AbstractFor the first time theoretical (in terms of the classical theory of ordering) and experimental (with the adiabatic calorimeter method) investigations are made of the effect of a third component impurity C on the heat capacity of A3B‐type ordered alloys with FCC structure. The effect of the impurities Mn, Cr, Mo, or W on the heat capacity of Ni3Fe alloys is analysed as an example. The comparison of the theoretical results with the experimental data shows good qualitative agreement.
Calculation of the Auger Spectra of Clusters Modelling Solid Hydrogen Fluoride
Authors: Liegener C. ‐M. 
Published: July 2007

AbstractThe Auger spectrum of solid hydrogen fluoride is calculated by an ab initio Green's function method. Already small clusters lead to saturation with respect to cluster size. The differences which arise when going from the gas to the solid phase Auger spectrum are mainly a broadening of the lines and the emergence of an additional feature at high kinetic energies. This additional feature is assigned to transitions to delocalized final states.