bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Model of Crystallization in a One‐Dimensional Classical Liquid
Authors: Maćkowiak J. 
Published: July 2007

AbstractA one‐dimensional classical mean‐field model of a liquid is presented. Each particle is located within its own cell on a circle and interacts with the others via a long‐range potential which tends to attract it towards the centre of the cell. The free energy of the liquid per particle is equal in the thermodynamic limit to that of a noninteracting system which exhibits a first‐order phase transition accompained by a discontinuous fall of the entropy and increased mean field characterizing an almost periodic particle distribution.
Thermodynamical Characteristics of Liquid Metal Droplets
Authors: Yakubov I. T. , Khrapak A. G. , Pogosov V. V. , Trigger S. A. 
Published: July 2007

AbstractA gradient expansion of free energy for simple metals is performed in the framework of the density functional method. The temperature behaviour of the surface tension is described reasonably for alkali metals and the temperature dependences are obtained for the electron work function. Effects due to the surface curvature are investigated. Some exact equalities are obtained which relate the first‐order curvature corrections to the surface tension and the work function to the characteristics of the flat surface. The first‐order curvature correction to the surface tension is calculated.
Transfer Matrix in 1D Schrödinger Problems with Constant and Position‐Dependent Mass
Authors: Pérez‐Alvarez R. , Rodriguez‐Coppola H. 
Published: July 2007

AbstractThe transfer matrix method is considered for obtaining properties of standard wells and barriers in one‐dimensional Schrödinger problems with constant and position‐dependent mass. The formulae for the energy levels of a well and the transmission coefficient of a barrier are given. The continuity is demonstrated between virtual bound states in a well of position‐dependent mass and the relation between the zero energy gap states of a periodic potential problem with the corresponding energies of the non‐periodic one's with transmission coefficient equal to one. The calculations are carried out for a wide class of potentials profiles.
Transfer Matrix in the Quasiclassical Approximation with Constant and Position‐Dependent Mass. Resonant Tunneling
Authors: Pérez‐Alvarez R. , Rodriguez‐Coppola H. , López‐Gondar J. , Lago‐Izquierdo M. 
Published: July 2007

AbstractA quasiclassical approximation is developed for the effective Hamiltonians describing nonhomogeneous systems and the wave function, the applicability conditions and the connection rules around the turning points are deduced. Based on the transfer matrix (TM) formalism expressions are obtained for the transmission coefficient of multiple barriers, the energy levels of multiple wells, and the quasistationary levels of a well open by one and by two sides. The dispersion relation of a periodic potential profile with variable mass problem is also given. Resonant tunneling is discussed for a system of multiple barriers. The transmission coefficient of such a barrier is maximum at energies close to the levels of the inner well when the end barriers are high enough and symmetric.
Diamagnetic Shift of Bielectrons in BiI3
Authors: Röseler J. , Shekhmametev R. I. , Neugebauer J. 
Published: July 2007

AbstractIn BiI3 the n = 5 and n = 6 lines of the inverse hydrogen‐like transmission spectra show a negative diamagnetic shift at 4 K for magnetic field strengths up to 50 T. Within the bielectron model the diamagnetic shift of such quasiparticle is calculated explicitly for higher‐excited states. The found results allow a satisfying quantitative explanation of the experimental findings.
Approximations to the Systematic Many‐Beam Case of High‐Energy Electron Diffraction. II. Improved Three‐Beam and Four‐Beam Solutions and Extinction Data
Authors: Kästner G. 
Published: July 2007

AbstractKinematical many‐beam corrections to the dynamical three‐beam and four‐beam approximations are derived analytically. The solutions yield refined extinction lengths and Bloch‐wave excitation coefficients tabulated for a variety of crystals and accelerating voltages (100 kV to 1 MV). Moreover, the results are used to analyse three‐beam and four‐beam features of electron transmission and anomalous absorption, and to represent many‐beam influences to critical‐voltage effects.
Dark Instability of F‐Centres in Pressure‐Treated KCl and KBr Crystals
Authors: Bagduev E. G. , Korovkin E. V. , Peresada G. I. , Ponyatovskii E. G. , Shikhsaidov M Sh. 
Published: July 2007

AbstractDark instability of colour is observed after the pressure treatment (phase transition from the NaCl‐type phase to the CsCl‐type phase and back) of coloured γ‐irradiated KCl and KBr crystals and additively coloured KCl crystals. The crystal bleaching is followed by luminescence and is strongly temperature dependent. The thermoluminescence method is employed in the studies. It is concluded that the pressure treatment leads to the formation of a great number of complex defects on the base of interstitial halide of which the diffusion or decomposition into simpler and more mobile defects leads to the phenomena observed.
Line Forces and Dislocations in Anisotropic Elastic Composite Wedges and Spaces
Authors: Ting T. C. T. 
Published: July 2007

AbstractA composite wedge or a composite space is considered which consists of n wedges of different anisotropic elastic materials and wedge angles. For the composite wedge, a line force is applied at its wedge apex while the sides of the composite wedge is traction free. For the composite space, a line force and a line dislocation are applied at the center. In both cases, explicit solutions in real form are obtained for the displacement, the displacement gradient, the stress function and the stress. This is achieved by the new sum rules presented here. In most literatures, the stress in a homogeneous anisotropic elastic space subject to a line force or a line dislocation is obtained indirectly through the displacement gradient and the stress–strain laws. In this paper the stress is obtained directly from the stress function. An interesting result is that the surface traction on any radial plane vanishes for the composite wedge. For the composite space, the surface traction on any radial plane depends on r only and is invariant with respect to the choice of the radial plane.
Phase Transition and Anharmonic Properties of Semimagnetic Semiconductors
Authors: Singh R. K. , Prabhakar N. V. K. 
Published: July 2007

AbstractThe phase transition and anharmonic properties are investigated of semimagnetic semiconductors Cd1–xMnxTe and Cd1–xZnxTe using a three‐body force potential. The calculated values of third order elastic constants follow a systematic trend of variation with molar concentration. The values of the phase transition pressures and the pressure derivatives of second order elastic constants show reasonably good agreement with their experimental data. The possible ways of improvements are also discussed.
Phonon Spectrum in Metastable F.C.C. Lanthanum
Authors: Onwuagba B. N. 
Published: July 2007

AbstractIt is observed in the framework of the model pseudopotential method that the off‐diagonal components of the interatomic potentials φ(sd)‐f and φf‐(ds) associated with the s–d and d–s interactions in the s and d‐electrons make significant contribution via the local fields in the phonon spectrum of metastable f.c.c. lanthanum. The magnitude of this attractive component screens the conventional Born‐Mayer potential. Numerical results give a good agreement with experiment in f.c.c. La.
The Peculiarities of the Electronic Structure of the La2–xSrxCuO4 Compound
Authors: Timoshevskii A. N. 
Published: July 2007

AbstractThe electron structure of La1.8Sr0.2CuO4 ceramics is theoretically studied by the cluster approach. It is found that the unoccupied 4f‐shell of La atom is located near the Fermi level which seems to be the reason of the unique physical properties of the above compound.
Hot Electron Magnetophonon Resonances in Conduction and Noise for a Nondegenerate Semiconductor
Authors: Cui H. L. , Lei X. L. , Horing N. J. M. 
Published: July 2007

AbstractThe nonlinear transverse magnetoresistivity of conduction electrons subject to inelastic scatterings by longitudinal optical phonons in a non‐degenerate semiconductor is determined using a balance equation approach. Magnetophonon resonances are examined in both, the linear and nonlinear transverse magnetoresistivities; and the electron temperature in an intense electric field is calculated as a function of the magnetic field, showing significant electron resonant cooling. The nonlinear current saturation in a high electric field is also studied, and is shown to be independent of the magnetic field. The thermal noise temperature for hot electrons at a nonzero bias is also examined, and exhibit its oscillatory behavior as a function of magnetic field.
Negative Magnetoresistance of Neutron‐Transmutation‐Doped Gallium Arsenide at Variable‐Range Hopping
Authors: Rentzsch R. , Friedland K. J. , Ionov A. N. 
Published: July 2007

AbstractInvestigations of anomalous magnetoresistance (mr) in neutron‐transmutation‐doped GaAs are performed at T = 0.05 to 4.2 K in the vicinity of the metal–insulator transition (MIT). Without as well as with magnetic field a variable‐range hopping‐law ϱ(T) = ϱ0 exp (T1/T)1/2 is found with T1 → 0 at n → nc. At low magnetic field a negative mr and for the first time T1(H) < T1(0) is found. At higher magnetic fields the negative mr saturates and eventually changes into a positive mr with T1(H) > T1(0). The dependence of T1 on n as well as on H originates from the scaling behaviour of the localization radius a and the dielectric constant ϵ0 at the MIT. From the extrapolation of the T1‐curves versus n(T = 300 K) to zero without and with magnetic field nc(H) is determined. In the range of negative mr no shift of nc with H is found. For positive mr, however, nc(H) > nc(0) = 2.18 × 1016 cm−3 is obtained. The scaling behaviour of the conductivity of barely metallic samples extrapolated to T = 0 gives for the critical index v = 0.84 ± 0.05. The comparison of v with the critical index b for the scaling relation of T1 gives the critical index ξ for the dielectric constant ξ = 1.55 and ξ/ν = 1.94.
Influence of Residual Resistance Measurements on the Superconducting Transition of Ultra‐High‐Purity Niobium
Authors: Fellmuth B. , Elefant D. 
Published: July 2007

AbstractA new surprising phenomenon is discovered investigating the superconducting transitions of ultra‐high‐purity niobium single crystals (reciprocal residual resistance ratio up to 53000). It can be detected that inductively measured transition curves are broadened by more than two orders of magnitude only by the simultaneous influence of the transport current and the external magnetic field (Ha > H) applied at measurements of the residual resistance using usual experimental technique. This broadening is caused by a change of the superconducting parameters in a surface layer with a thickness of only some μm. The reproducibility of the phenomenon and the spatial dependence of the superconducting parameter change in the surface layer are carefully investigated. An interpretation of the broadened transition curves is carried out on the basis of the phenomenological Ginzburg‐Landau theory. The results obtained lead to the conjecture that the phenomenon is connected with the transition from the Meissner state to the Shubnikov state in the presence of a transport current.
Mean Field Renormalization Group for Site‐Bond Diluted Ising Ferromagnets
Authors: Yang C. Z. , Li Z. Y. 
Published: July 2007

AbstractIt is shown that the mean field renormalization group techniques provide a reasonable description of the critical behaviour of the site‐bond diluted Ising model, both in the two‐dimensional system and the surface of a semi‐infinite three‐dimensional system.
Phase Diagrams of an Amorphous Ferromagnetic Insulator with a Fractional Effective Coordination Number
Authors: Kaneyoshi T. 
Published: July 2007

AbstractAn amorphous spin‐one Ising ferromagnetic insulator with a fractional effective coordination number is studied by the use of an effective‐field theory with correlations. The influences of random bond and crystal‐field interaction on Curie temperature and tricritical point are investigated. A number of interesting phenomena in these quantities is found. It is suggested that the research of such an insulator may open a new field of magnetism.
Spin Dynamics in the Classical Easy‐Plane Antiferromagnet Proton Spin–Lattice Relaxation in TMMC
Authors: Gouvea M. E. , Pires A. S. T. 
Published: July 2007

AbstractA spin wave calculation of the memory function for the classical anisotropic one‐dimensional antiferromagnetic Heisenberg model is applied in a calculation of the temperature dependence of the spin–lattice relaxation rate in TMMC [(CH3)4N]MnCl3. Comparison with experiment is made.
Spectroscopic Determination of the Hindered Rotational Behavior of the CN− in Alkali Halides
Authors: Wilk S. R. , Lüty F. 
Published: July 2007

AbstractThe rotational properties of CN− substituted into various alkali halide matrices are studied through the rotational‐vibrational second harmonic absorption and excitation spectra at 2.4 μm of its vibrational emission. The variation of the spectral width with temperature is measured through the separation of the R‐ and P‐branches, the full width at half maximum, or the second moment of the spectra. The onset of T1/2 variation of the width provides a direct, if rough, measurement of the height of the barrier hindering quasifree rotation. This barrier varies from 20 cm−1 in KI to 85 cm−1 in CsCl. The coefficients of T1/2 yield the rotational constant, which varies from 0.16 cm−1 in CsI to 1.36 cm−1 in KCl. Since all measured values fall below the expected free CN− value of 1.94 cm−1, the effective moment of inertia must be increased by some mechanism, among which dressing of the ion's moment of inertia by participation of the surrounding lattice ions in rotational motion is judged to be most likely.
Band Edge Absorption Saturation Dynamics of Semiconductors
Authors: Kochelap V. A. , Kulish N. R. , Lisitsa M. P. , Malysh N. I. , Sokolov V. N. 
Published: July 2007

AbstractTemporal evolution of the transmission coefficient and of the output light intensity during the laser pulse is investigated for CdSe single crystals. The nonlinear bleaching observed in the Urbach region of the absorption spectrum at room temperature has a threshold character. With the increase of the laser pulse energy exceeding the threshold value ℰ1, the transmission coefficient at first experiences a strong rise and then reaches a saturation. A phenomenological model describing the observed features is proposed assuming an abrupt dependence of the absorption coefficient on the photoexcitation density. The sequence of dynamical relationships between the transmission and the pump level is quantitatively analysed. From experimental data the threshold specific energy and the specific energy required for the bleaching of a 100 μm sample are deduced. They are equal to 2.2 × 10−11 and 1.9 × 10−10 J/μm2, respectively.
Soliton and Breather Dynamics in a Nematic Liquid Crystal under the Action of Constant and Time‐Varying Magnetic Fields
Authors: Abdullaev F. Kh. , Abdumalikov A. A. , Tsoi E. N. 
Published: July 2007

AbstractThe soliton and breather dynamics in a nematic liquid crystal under the action of constant and time‐varying magnetic fields are investigated. The two cases are considered: with highest gradient terms in the free energy and without them. The action of addition magnetic fields and dissipation are considered using the perturbation theory for solitons and breathers. A condition for chaotic oscillation of director is obtained. Absorption of the external alternating‐field energy in the linear approximation is studied.
Dynamics of Ionic and Bonding Defects in Quasi‐One‐Dimensional Hydrogen‐Bonded Chains
Authors: Kristoforov L. N. , Zolotaryuk A. V. 
Published: July 2007

AbstractThe motion of extended ion (orientational) defects in quasi‐one‐dimensional hydrogen‐bonded chains is studied for the double‐well potential model of a proton in the presence of applied external fields.
Energy Band Structure of (GaAs)m (AlAs)m Semiconductor Superlattices with Ultrathin Layers
Authors: Gushchina N. A. , Dunaevskii S. M. , Nikulin V. K. 
Published: July 2007

AbstractThe local band structure of the (GaAs)m (AlAs)m superlattices is calculated within the framework of the cluster recursion method of Haydock‐Heine‐Kelly. The Hamiltonian is constructed in the sp3s*‐basis of the tight‐binding method. The diagonal matrix elements and orbital populations are calculated in a self‐consistent way. The superlattice consists of alternate layers of GaAs and AlAs, each containing one to eight (110) layers of zincblende structure. The limiting cases of such a superstructure are the ideal heterojunction and a semiconductor material made up of alternate GaAs and AlAs layers. The paper presents the calculated densities of electron states for (GaAs)1 · (AlAs)1 and band discontinuities at the heterojunction. The dependence of the superlattice energy gap width on the alternate layer thickness derived here is in qualitative agreement with the experimental photoluminescence data.
On Electron States of Quantum Wells in Ultrathin Films of Wide‐Gap Semiconductors in an Oriented Magnetic Field
Authors: Bose M. K. , Majumdar C. , Maity A. B. , Chakravarti A. N. 
Published: July 2007

AbstractAn attempt is made to investigate the effects of a tilted magnetic field on the size‐quantized levels of quantum wells in ultrathin films of wide‐gap semiconductors, taking n‐GaAs as an example. It is found that the energy eigenvalue of the lowest Landau level corresponding to a given electric subband increases with increasing magnetic field, and reaches a maximum corresponding to a given orientation of the field, the dependence being increasingly prominent with increasing size quantum numbers. Besides, the eigenvalue corresponding to the lowest electric subband decreases with increasing film thickness, the rate of decrease being significantly dependent on the magnetic field and its orientation.
Size‐Quantized Excitons in Microcrystals of Cuprous Halides Embedded in Alkali‐Halide Matrices
Authors: Itoh T. , Iwabuchi Y. , Kirihara T. 
Published: July 2007

AbstractExciton luminescence spectra in CuCl, CuBr, and CuI microcrystals of a few nm in size which are embedded in alkali‐halide matrices are studied under selective excitation at the exciton absorption bands inhomogeneously broadened by the size distribution. The size‐quantized exciton states are found to split into various components. From the analysis of the splitting on the basis of the size‐quantization of the exciton translational motion in the microcrystals of thin platelets, the Z3 exciton translational mass, the Luttinger parameters, and k‐linear terms for the Z1,2 excitons are derived in these compounds.
On the Dynamical Stark Effect of Excitons. The Low‐Field Limit
Authors: Zimmermann R. 
Published: July 2007

AbstractThe dynamical Stark effect of excitons in semiconductors is treated in three and two dimensions (bulk material and MQW structures, respectively). Within the low‐field limit, theoretical results are presented for the gap function, the excitonic enhancement of the Stark shift, and the induced density. Higher bound states and the excitonic continuum are fully taken into account using the Coulomb Green's function.
Evolution Equations for Highly Excited Direct Semiconductors in the Athermal Stage
Authors: Heiner E. 
Published: July 2007

AbstractA consistent extended time‐dependent mean field theory (TDMF) is introduced for the description of the evolution in the athermal stage of a direct semiconductor during and after a short laser pulse. A general theory involving dissipation and nonlinearity is developed from first principles. The form of the evolution equations is determined by the algebraic structure of the observation level. The collision terms are treated in a short memory approximation (SMA).
Semiconductivity in the Liquid Cu–TlTe System
Authors: Satow T. , Ishikawa H. , Uemura O. 
Published: July 2007

AbstractMeasurements of the electrical conductivity, the magnetic susceptibility, and the thermoelectric power for the liquid Cu–TlTe system are made in wide temperature and composition ranges. It is observed that the conductivity for the system falls abruptly at the composition of 50 mol% Cu and the themoelectric power changes its sign around this composition. The diamagnetic susceptibility also shows a sharp maximum at the corresponding composition. The experimental results of the present work are compared with the previous data of liquid telluride systems and are discussed in the light of current transport theories employed in amorphous and liquid semiconductors.
The Effect of Structural Imperfections on Macroscopic Properties of Tellurium‐Type Anisotropic Semiconductors
Authors: Shenderovskii V. A. , Tomchuk P. M. , Gorley P. N. , Gavaleshko N. P. , Tarasyuk I. I. 
Published: July 2007

AbstractA theory of transport phenomena for anisotropic semiconductors is developed in which inelastic carrier scattering is dominating and the Debye screening radius of defects is large compared with the carrier mean free path. The effect of edge dislocations on electrical conductivity, magnetoresistance, and transverse and longitudinal Nernst‐Ettingshausen effects is investigated using tellurium as a model semiconductor. The defects are found to considerably affect the electrical conductivity of Te depending on the magnitude and the direction of magnetic field.
On Anisotropy of Nuclear Spin‐Diffusion Coefficient
Authors: Butkevich E. R. , Sabirov R. Kh. 
Published: July 2007

AbstractThe anisotropy of the spin diffusion coefficient for the simple cubic lattice is investigated. The analysis is based on using the non‐equilibrium statistical operator method. The form of the correlation function, which determines the spin diffusion coefficient, is treated by the momentum method. Exact expressions for the second and fourth moments are obtained. It is shown that usually using the Gaussian form of the correlation function as usually is unsatisfactory. Therefore, the known conclusion about the absence of anisotropy of the spin diffusion coefficient does not take place. Values of the spin diffusion coefficients are presented.
The Local Correlation Lengths in Ising Models with Free Surfaces
Authors: Korneta W. , Pytel Z. 
Published: July 2007

AbstractThe nearest‐neighbor Ising model of a film is considered in which couplings between spins depend on the distances to the surfaces. The local correlation lengths in directions parallel and perpendicular to the surfaces of the model near different second‐order phase transitions are studied. The random‐phase approximation is used. Analytical expressions for the local correlation lengths are obtained. Assuming that one surface of the model of a film tends to infinity, local correlation lengths in the three‐dimensional semi‐infinite Ising model are obtained.
Quantum Tunneling between AF and SF or Equivalent States in a Uniaxial Antiferromagnet
Authors: Prystasz W. 
Published: July 2007

AbstractStudies are continued of tunneling effect at the first order phase transitions in the antiferromagnet with external magnetic field. By using quasiclassical approximation (WKB formalism) the probabilities are derived of the tunneling transitions between equivalent antiferromagnetic states and equivalent spin flop states. The probabilities of the tunneling transitions between the antiferromagnetic and spin flop phases are also calculated.