bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cohesive Energies, Equation of State, and Thermoelastic Properties of Mixed Alkali Halide Crystals
Authors: Dixit S. , Niwas R. 
Published: July 2007

AbstractThe cohesive energies and equations of state describing the pressure‐volume relations are studied for nine systems of mixed alkali halide crystals for the entire range of composition. The Harrison analytical potential form for the overlap repulsive energy derived from quantum mechanical considerations is used to describe the nearest neighbour as well as next neighbour interactions. The long‐range electrostatic and the short‐range van der Waals interactions are also considered in the potential model. The thermoelastic properties such as the Grüneisen parameter and its volume derivative, isothermal and isentropic Anderson parameters are also calculated and reported. The results are discussed and compared with experimental data.
Magnetotransport Properties and Subband Structure of the Two‐Dimensional Electron Gas in the Inversion Layer of Hg1−xCdxTe Bicrystals
Authors: Kraak W. , Kaldasch J. , Gille P. , Schurig Th. , Herrmann R. 
Published: July 2007

AbstractThe electronic and magnetotransport properties of conduction electrons in the grain boundary interface of p‐type Hg1−xCdxTe bicrystals are investigated. The results clearly demonstrate the existence of a two‐dimensional degenerate n‐type inversion layer in the vicinity of the grain boundary. The observed quantum oscillations of the magnetoresistivity result from a superposition of the Shubnikov‐de Haas effect in several occupied electric subbands. The occupation of higher subbands is presumable depending on the total carrier density ns of the inversion layer. Electron densities, subband energies, and effective masses of these electric subbands in samples with different total densities are determined. The effective masses of lower subbands are markedly different from the band edge values of the bulk material, their values decrease with decreasing electron density and converging to the bulk values at lower densities. This agrees with predictions of the triangular potential well model and a pronounced nonparabolicity of the energy bands in Hg1−xCdxTe. At high magnetic fields (B > 10 T) it is experimentally verified that the Hall resistivity ϱxy is quantized into integer multiplies of h/e2.
Equilibrium and Kinetics of Ion Exchange in Zinc Selenide Single Crystals
Authors: Aleksanyan A. O. , Ganshin V. A. , Korkishko Yu. N. , Fedorov V. A. 
Published: July 2007

AbstractThe process of ion‐exchange Cd2+ ⇄ Zn2+ in ZnSe single crystals is studied for the first time. A mixture of K2SO4Na2SO4ZnSO4 is used as doping melt. It is shown that the CduZn1−uSe solid solution formed in the surface region of the crystal as a result of the ion exchange has zinc‐blende structure at all values of u and is regular. The thermodynamical and diffusion‐kinetic parameters of exchange and diffusion stage of the process in the temperature range from 400 to 500 °C are determined.
Role of Electron‐Phonon Interaction Induced Hybridisation in Spin Included Mixed‐Valence Phenomena
Authors: Ghosh S. C. , Ghosh N. K. , Sarkar R. L. 
Published: July 2007

AbstractThe phenomenon of valence transition is investigated on the basis of a model which incorporates the electron‐phonon interaction induced hybridisation between f and d bands. Finite temperature specific heat, magnetic intersite spin correlations are also studied. It is shown that strong EP interaction makes the first‐order transition possible. A comparison is also made with results obtained previously.
Non‐Relativistic and Scalar‐Relativistic LAPW Electronic Energy Bands of (001) Cu Films
Authors: Dubrovskii O. I. , Kurganskii S. I. , Rubtsova L. A. , Wolf G. W. 
Published: July 2007

AbstractThe band structures of 1‐, 3‐, and 5‐layer f.c.c. (001) Cu films are calculated using the linearized augmented‐plane‐wave method both, in the non‐relativistic and the scalar‐relativistic modification. The one‐electron potential of the Kohn‐Sham equation, constructed using the film “muffin‐tin” approximation is the same for both the cases. The account of relativistic effects is shown to result in the nearly homogeneous ≈ 16 mRy shift of the energy spectrum towards lower energies.
Calculation of the Normal‐State Thermal Conductivity of the Lattice for High‐Tc Superconductors
Authors: Schiller W. , Weschke K. 
Published: July 2007

AbstractStarting from the method of inverse linear response theory the thermal conductivity of the lattice is calculated for the anharmonic model of high‐Tc superconductors with structurally unstable lattices. This model describes the interaction between strong anharmonic ion vibrations and the electron system. The contribution of this interaction and a contribution due to the structure of the anharmonic model determine the properties of the lattice thermal conductivity. The influence of both scattering mechanisms on the temperature behaviour in the normal‐conducting phase is considered. Results for different parameters of the anharmonic model are discussed and compared with experimental investigations on YBaCuO compounds.
Transport with Microscopic Inhomogeneities. Residual Resistivity Dipole, Landauer Formula, and the Three‐Dimensional Impurity Case
Authors: Lenk R. 
Published: July 2007

AbstractA superposition method for the density matrix of stationary transport processes is developed where an arbitrary perturbation is superimposed on a weakly scattering background. Additional scatterers, areal perturbations of the grain boundary type and/or geometrical confinements in wires or films are candidates for applications. In the present paper an arbitrarily strong added scatterer is treated whose linear size remains small compared with the mean free path within the background. This problem is solved for a one‐channel quantum wire and for the three‐dimensional bulk. In both cases the evolving residual resistivity dipole (RRD) is determined. Already existing results are confirmed, generalized, and complemented by the inclusion of oscillatory density terms. A comparison of both the cases demonstrates the decisive role played by the topology of the problem. Within the scope of a completely formalized nonclassical transport theory, the internal mechanism producing the RRD is analysed. In this way it is shown that the voltage drop due to an added scatterer is given correctly, in the one‐channel case, by an expression of the (R/T)‐type quite similar to the original Landauer formula (LF). This derivation of a modified LF abandons the concept of dissipative reservoirs and ideal leads. The physical difference between ideal and resistive leads yields different results, too. These agree completely only for a sharp Fermi energy while, in the general case of finite temperatures, non‐negligible energy dependences destroy the full equivalence of both approaches.
Drag Effects in Semiconductors with Position‐Dependent Band Structure
Authors: Istrate Mariana , Istrate S. 
Published: July 2007

AbstractIn a semiconductor with position‐dependent band structure if on take into account the drag effects, the expressions for the kinetic coefficients contain terms in addition to those corresponding to the conventional components for such semiconductors. These expressions are developed for a nondegenerate and a degenerate semiconductor, in the case of a phonon—phonon drag. The relations can be used for a variety of materials including graded band gap semiconductors, graded heterojunctions and others.
Spin‐1 Exchange Interaction Model of Ferromagnetism
Authors: Chaddha G. S. , Singh J. 
Published: July 2007

AbstractEffects of biquadratic exchange on the low temperature behaviour of magnetisation, Curie temperature, and zero field susceptibility at high temperatures are investigated in the case of a spin‐1 Heisenberg ferromagnet. The Green function technique with mixed Callen and RPA decoupling approximations is utilized. Some invalid results and drawbacks of earlier treatments are noted.
Interband Resonance Raman Scattering in p‐Type Semimagnetic Semiconductors in Quantizing Magnetic Field
Authors: Gashimzade F. M. , Ismailov T. G. , Nadirzade R. S. 
Published: July 2007

AbstractThe electron Raman scattering in the wide‐gap semimagnetic semiconductor p‐Cd1−xMnxTe in a quantizing magnetic field is studied. Expressions in analytical form for the differential effective cross section depending on frequency shift are obtained. The possibility of determination of exchange parameters from experiment is shown.
Evidence for Order Parameter Spatial Fluctuations in TlGa(Se1−xSx)2 Crystals by Raman Spectroscopoy
Authors: Burlakov V. M. , Anikiev A. A. , Yakheev M. R. 
Published: July 2007

AbstractRaman spectra of the ferroelectric layered crystals TIGa(Se1−xSx)2 are studied for concentrations x = 0, 0.05, 0.15 over a wide temperature range. The contribution of the order parameter spatial fluctuations to the spectral line parameters is defined by comparing the concentration dependence of the low‐frequency integral intensity to that of the splitting of a doubly degenerated hard mode at ≈ 55 cm−1. Large spatial fluctuations of the order parameter are assumed to be caused by the presence of an order–disorder component in the ferroelectric instability of the layered crystal. The order—disorder component is thought to be related to a narrow one‐dimensional soft phonon band.
Temperature Dependence of the Oxygen Absorption Band in ZnTe: O
Authors: Slusarenko V. , Burki Y. , Czaja W. , Berger H. 
Published: July 2007

AbstractAbsorption measurements are made as function of temperature for the isoelectronic trap ZnTe: O. This spectrum is well separated from the intrinsic absorption and from the absorption due to other impurities. The spectra can be semiquantitatively understood using a model developed for AgBr:I. The temperature dependence of the absorption due to LO‐phonon cooperation is given by ∼e−γT2 where γ can be derived from the value for AgBr:I. The fine structure of the absorption is explained and the spectral symmetry between emission and absorption is discussed in detail. The electron—phonon coupling (Huang‐Rhys factor) is found to be different for different phonon modes and smaller in absorption than in emission for optical modes but the inverse is true for accoustic modes.
Lattice Dynamics and Phonon Dispersion in the Narrow Gap Semiconductor Bi2Te3 with Sandwich Structure
Authors: Kullmann W. , Eichhorn G. , Rauh H. , Geick R. , Eckold G. , Steigenberger U. 
Published: July 2007

AbstractThe extremely anisotropic bonding properties of the narrow gap semiconductor bismuth telluride (Bi2Te3) with sandwich structure is studied by inelastic neutron scattering. In combination with lattice dynamical shell model calculations, new information is obtained on the complex bonding forces of this sandwich structured V–VI semiconductor. The sandwich character leads predominantely to three‐dimensional bonding behavior. No characteristic two‐dimensional lattice properties can be observed.
Analysis of Ionic Radii, Second Neighbour Interactions, and Electronegativity Difference for Ionic Crystals
Authors: Singh B. P. 
Published: July 2007

AbstractValues of ionic radii are determined using the additivity rule and experimental information on X‐ray diffraction and electron density measurements for NaCl crystals. The calculated values of ionic radii are found to produce the nearest‐neighbour interionic separations close to the experimental values in I–VII, II–VI, and III–V compounds. In order to demonstrate the suitability of the calculated radii the interionic distances in tri‐atomic compounds are also predicted. The second‐neighbour overlap repulsive interactions and electronegativity differences are discussed in terms of ionic radii. The calculated radii are found to correlate very well with the electronegativity differences.
Isostructural γ‐α Transition in Metallic Cerium as a Mott Transition
Authors: Ionova G. V. , Nikolaev A. V. 
Published: July 2007

AbstractThe isostructural γ–α phase transition of Ce is studied by means of FLAPW band calculations carried out for four different electronic structures of Ce. The calculated results support the picture of a 4f localized‐itinerant transition at the γ–α transition.
Fermi Surface and Mass Enhancement Factor for Niobium
Authors: Solanki A. K. , Ahuja R. , Auluck S. 
Published: July 2007

AbstractCalculations of the extremal areas of Fermi surface orbits in the transition metal niobium (Nb) are presented using the ab initio linear muffin tin orbital method in the atomic sphere approximation and including the combined correction terms. Self‐consistent calculations are performed using various exchange‐correlation (XC) potentials. The Xα exchange‐correlation potential (with α = 0.75) gives the best agreement with the experimental data. The anisotropy of the Fermi velocity of electrons at the Fermi surface and the mass enhancement factor are also calculated using this XC potential. These are compared with the experimental data and recent theoretical calculations.
Self‐Consistent Calculation of Density of States in Impure Semiconductors
Authors: Grill R. 
Published: July 2007

AbstractUsing the Kadanoff‐Baym Green's function formalism the density of states function is calculated. The calculation is performed for the heavy hole band and screened charged impurity scattering in the Born approximation. The results are shown for p‐HgCdTe semiconductor. It is argued that a qualitative change of the band near the edge is essential for a band occupation.
Auger Recombination via Defects in Tellurium
Authors: Mazur Yu. I. , Rubo Yu. G. , Snitko O. V. , Strikha M. V. 
Published: July 2007

AbstractAuger process including a bound electron and two free holes proved to be the dominant recombination path in tellurium at low temperatures (T < 50 K). The experimental value of the Auger constant is C = 1.6 × 10−28 cm6 s−1. The theoretical model considering the tellurium band structure explains the experimental data qualitatively and gives an order of magnitude value for the lifetimes of excess carriers.
Theory of Transport Phenomena in Ferromagnetic Semiconductors with Superlattice Produced by Coherent Light Beams
Authors: Semchuk A. Yu. , Grechko L. G. , Ogenko V. M. 
Published: July 2007

AbstractThe present paper deals with the effect of a superlattice of non‐equilibrium electrons and magnons on transport phenomena in ferromagnetic semiconductors (FMSC). Such superlattices are formed by coherent light beams (CLBs). A general expression is derived for an additional current in FMSC, caused by the presence in FMSC of superlattices of the carrier concentration, electric field strength, electron, and magnon temperatures. The field dependence of the electrical conductivity of FMSC on superlattices is investigated.
Non‐Resonant Microwave Absorption in N = 3 Phase of BiPbSrCaCuO High‐Temperature Superconductor
Authors: Owens F. J. 
Published: July 2007

AbstractA detailed study is made of the temperature and magnetic field dependent properties of the non‐resonant microwave absorption in granular composites of the N = 3 phase (Tc = 110 K) of the high‐temperature supercondutor Bi2−xPbxSr2CaN−1CuNO4 + 2N using an EPR spectrometer. The magnetic field value of the center of the line and the width of the line depend on the magnitude of the previously applied dc magnetic field and the direction of sweep of the field. The position and width also change with temperature. It is shown that the theory of Xia and Stroud for the electromagnetic response of superconducting current loop in an increasing magnetic field, assuming a Boltzmann distribution of loop areas in the granular composite, can account for the shape of the derivate and the temperature dependence of the intensity of the derivative of the absorption. The change of the magnetic field position and linewidth with temperature and field can not be accounted for by the theory. These effects are argued to be a result of the flux trapping behavior of the sample.
Ensemble Averaged Moments and Autocorrelation of the Actual Static Factor
Authors: Schulz M. , Handrich K. 
Published: July 2007

AbstractFor various problems of disordered systems one needsmore information, than that contained in the staitc structure factor S(k). Therefore, and actual static structure factor s(k) is defined, which is connectted to the static structure factor S(k) by the average S(k)=〈s(k)〉. The correlation function 〈s(k)s(k′)〉, all moments 〈s(k)n〉, and the probability distribution of s(k) are determined.
Estimation of the Leading Order Anharmonic Parameters from Available Thermodynamic Data
Authors: Mulargia F. , Quareni F. 
Published: July 2007

AbstractA procedure is presented to estimate from available thermodynamic data the leading order anharmonic coefficients, their volume derivatives, and the quasi‐harmonic terms in the framework of perturbation theory of lattice dynamics to the fourth order in the Hamiltonian. It consists of fitting the theoretical expressions of three functions of compressibility, heat capacity, and thermal expansion to experiment particularly tailored to minimize the effect of experimental errors. The capability of the procedure to produce stable and accurate results is tested through an application to NaCl. NaCl is chosen because of the large number of available independent data, which allows to study in detail the effect of external as well as internal errors. Accurate estimates are found to be possible. Referred to the 300 K volume and on the basis of all available data, the resulting leading order anharmonic parameters of NaCl are A2=(4.6 ± 0.6) x 10−4 J mol−1 K−2, dA2/d In V=(9 ± 4) x 10−4 J mol−1 K−2, while the quasiharmonic parameters are 〈ω〉=(6.8 ± 0.2) × 1026 s−2, 〈γi〉=1.57 ± 0.01, 〈γiωi2〉=(1.2 ± 0.1) × 1027 s−2.
Lattice Dynamics of the Force Constant Defect System Pd0.95Ru0.05
Authors: Maliszewski E. , Sosnowski J. , Bednarski S. 
Published: July 2007

AbstractThe lattice dynamics of a Pd0.95Ru0.05 single crystal is investigated at room temperature. The phonon dispersion relations along the directions [100], [110], and [111] are measured using the inelastic neutron scattering technique. The seven‐neighbour Born‐von‐Kármán model is fitted to the experimental branches and the force constants and elastic constants are calculated. The phonon frequency shifts, Δω(q), and the self‐energy functions, Σj (q, ωj(q)), are determined. From the comparison of the self‐energy functions for 5 and 10 at% Ru contents in Pd matrix the evolution of the self‐energy with the Ru concentration is clearly seen.
Dynamics of Electric Field Screening in Semi‐Insulating ZnSe
Authors: Astratov V. N. , Furman A. S. , Ilinskii A. V. , Repin S. M. 
Published: July 2007

AbstractThe dynamics of the screening of an external electic field in semi‐insulating ZnSe is studied. It is found that this dynamics exhibits two different regimes depending on the crystal temperature and the conditions of the preliminary illumination: expansion of the single homogeneous depletion layer or formation of numerous space charge layers of alternating sign. All these results are described within a simple model allowing for two types of deep centers with different recharging times.
On the Electronic Structure of Phosphorus in Nickel
Authors: Stepanyuk V. S. , Katsnelson A. A. , Kozlov A. V. , Farberovich O. V. , Szász A. , Kojnok J. 
Published: July 2007

AbstractThe electronic density of states of the NiP amorphous system is calculated in a self‐consistent way from first principles, using a KKR Green's‐function method with a single perturbed muffin‐tin potential in a periodic lattice.
Unthreshold Impact Ionization by Virtual Electrons in Semiconductors under Streamer Discharge Excitation
Authors: Voitikov S. V. 
Published: July 2007

AbstractImpact ionization of semiconductors under ultrafast electric‐field excitation at the streamer discharge front is theoretically investigated. It is shown that impact ionization is initiated by virtual electrons and is of unthreshold character unlike the known mechanisms of impact ionization in quasi‐stationary field. Amplitudes and probabilities of the interband transitions are calculated. The lack of threshold conditions permits the momentum transmitted at impacts between particles to be very small which results in the increase of interband transition probabilities and concentrations of non‐equilibrium carriers of charge. It is also shown that with increasing velocity of discharge propagation the intensity of ionization by virtual electron impact essentially increases, and the carrier concentrations achieve 10(16.5 ± 1.5) cm−3.
Cyclotron Resonance of a Magnetopolaron in a Polar‐Crystal Slab at Finite Temperatures
Authors: Wei Bao‐hua , Gu Shi‐wei 
Published: July 2007

AbstractTaking into account the interaction of an electron with both, bulk longitudinal‐optical (BO) and surface‐optical (SO) phonons, the cyclotron resonance of a magnetopolaron in a polar‐crystal slab at finite temperatures is investigated by using the generalized Larsen perturbation‐theory method. The temperature dependence is studied of the cyclotron resonance mass of a magnetopolaron in the resonant region of the GaAs slab.
Superconductivity in the Extended Hubbard Model
Authors: Bulka B. R. 
Published: July 2007

AbstractThe extended Hubbard model on a square lattice is considered in the framework of the mean‐field formalism. A detailed analysis of the stability of the superconducting state of the s‐ and the d‐type symmetry is performed for different band filling. Special attention is focused on the state with mixed sd‐type symmetry, which may occur at an intermediate strength of interactions.
Fluctuations of the Molecular Field in the Two‐Ion Model for Temperature‐Induced Metamagnets
Authors: Rudziński W. , Onyszkiewicz Z. 
Published: July 2007

AbstractA special quartic spin model of spontaneous metamagnetism, proposed by Onyszkiewicz is considered involving dipole‐octopole interaction between two neighbouring ions. The thermodynamic properties of this model are investigated, using the high‐density expansion method in the approximation including Gaussian fluctuations of the molecular field. The free energy, the magnetization, the octopole parameter as well as mean squares of fluctuations are calculated for A → F metamagnets. The results are then compared with those obtained by the molecular field approximation. Moreover, a comparison of the results with those obtained earlier for the so called four‐ion model confirm effectiveness of the two‐ion model also in such refined procedure as the Gaussian fluctuation approximation.
A New Random Surface Fractal for Applications in Solid State Physics
Authors: Hermann H. 
Published: July 2007

AbstractA new random surface fractal is developed. The construction is based on a Boolean model with spherical primary grains. The radii of the grains follow a distribution that can be approximated by a power‐law in the limit of small radii. The fractal dimension is estimated according to the Minkowski‐Bouligand definition. Volume fraction and two‐point correlation function of the fractal are derived exactly.
Shear Moduli of Macroisotropic Cubic Polycrystalline Materials
Authors: Sisodia P. , Dhoble A. , Verma M. P. 
Published: July 2007

AbstractThe effective shear moduli of the perfectly disordered polycrystalline cubic solids are determined by solving the well known cubic equation. The solids include perhaps all the cubic crystals for which single crystal elastic constant data are available at present. It is observed that the effective shear modulus can be empirically expressed as a simple function of the anisotropy parameter A and that a justification for such an expression can be derived from the cubic equation itself. It is further observed by analysing the cubic equation that (a) considering the shear modulus G to be independent of the bulk modulus B one would obtain bounds for G even narrower than the Hashin‐Shtrikman bounds and (b) that the VRH mean is quite close to the self consistent shear modulus for all the cubic solids.