bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical and Electrical Investigations of the Anisotropy of Sb2Te3 Single Crystals
Authors: Langhammer H. T. , Stordeur M. , Sobotta H. , Riede V. 
Published: July 2007

AbstractOn Sb2Te3 single crystals with conductivities between 3700 and 7000 Ω−1 cm−1 the anisotropy of the reflectivity of polarized infrared light, the anisotropy of conductivity and of the Seebeck and Hall coefficients are investigated. In addition to the excitation of free carriers in the reflection spectra of donor doped crystals also interband excitations are observed. In terms of a six‐valley band model with anisotropic scattering the contribution of the free carriers to the susceptibility is calculated, and the anisotropy ratio of the effective susceptibility masses magnified image is given. It is found that the anisotropy decreases with increasing conductivity. A comparison of magnified image with the anisotropy of conductivity σ ⊥c/σ‖c shows that for Sb2Te3 single crystals with σ‖σ ⊥c < < 5000 Ω−1 cm−1 the carrier scattering is anisotropic.
Theory of Interatomic Forces in Rare Gas Crystals
Authors: Shanker J. , Rajauria A. K. 
Published: July 2007

AbstractThe theory of interatomic forces in rare gas crystals is used to calculate the cohesive energy, the third‐order elastic constants, and the pressure derivatives of the second‐order elastic constants for Ne, Ar, Kr, and Xe. The method of Lehri and Verma based on the three‐body force model is revised. The results obtained are compared with the corresponding values determined by Zucker and Paik from a different model based on long‐range three‐body interaction terms. The cohesive energies calculated in the paper present good agreement with experimental data.
The CNDO/BW Study of Lithium Clusters II. B.C.C. Clusters
Authors: Skála L. 
Published: July 2007

AbstractThe CNDO/BW method is used for a detailed study of b.c.c. lithium clusters. The equilibrium distances between atoms, binding energies, one‐electron energies, charges at atoms, bond orders, and dipole moments are investigated for 13 clusters with 5 to 35 atoms. For greater clusters, an extrapolation of the results is used and discussed.
Nuclear Quadrupole Effect and Phase Transition in the Quasi‐One‐Dimensional Conductor β‐Na0.33 V2O5
Authors: Onoda M. , Takahashi T. , Nagasawa H. 
Published: July 2007

AbstractThe angular dependence of the main NMR resonance lines of the 51V nuclei in β‐Na0.33V2O5 is measured above and below the first‐order structural phase transition temperature in the frequency range between 10 and 20 MHz. The nuclear quadrupole interaction parameters of the broad resonance line are determined, and the principal axes of the electric field gradient tensor are found to coincide with those of the crystalline field around the vanadium atoms in site I.
On the Theory of Longitudinal Magnetoresistance of Metallic Films and Wires
Authors: Kogan E. M. , Ustinov V. V. 
Published: July 2007

AbstractThe quasiclassical kinetic equation for the conduction electrons distribution function and boundary conditions for this equation are written in “action‐angle” variables. It allows to obtain a relation between the boundary condition parameters and the quantum surface collision integral for conduction electrons with an arbitrary dispersion law. The use of the “action‐angle” variables is found to be very convenient for the conductivity calculation in films and wires in a longitudinal magnetic field. With their help general formulas for the longitudinal magnetoresistance both of films and wires with an arbitrary conduction electron dispersion law and an arbitrary surface scattering are obtained.
Calculation of the Electronic Density of States in Disordered Metallic Systems
Authors: Lai S. K. , Wang S. 
Published: July 2007

AbstractThe use of N(E) = NFEk(∂E(k)/∂k)−1 as the electronic density of states for disordered metallic systems is critically examined. The present examination shows that its use is reasonable and that the applicability of the nearly‐free‐electron theory to the binary alloys of simple metals becomes worse and worse in going from the case of small charge transfer to the case of large charge transfer.
Luminescence and Optical Investigation of NaF:Ce3+ Single Crystals
Authors: Bhan S. 
Published: July 2007

AbstractIt is observed that undoped NaF samples exhibit four glow peaks at 73, 120, 143, and 223 °C and NaF doped with Ce3+ samples exhibit an additional peak at 183 °C. The 73 °C peak is attributed to F'‐centres and the remaining peaks to F‐centres. Involvement of Ce3+ impurity is suggested in the origin of the 183 °C peak. Ce3+ impurity does not change its valence state on irradiation. It acts as an activator during luminescent process.
The Impact‐Parameter Dependence of Energy Losses in Proton Scattering by Gold Atoms
Authors: Iferov G. A. , Zhukova Yu. N. 
Published: July 2007

AbstractThe energy losses of protons scattered by atoms of gold are measured in the impact‐parameter range of 0.4 ≦ ϱ/αTF ≦ 4.0 where αTF is the Thomas‐Fermi radius. If the penetration depth of a proton into the electronic shell of an atom increases, there occurs a peculiar saturation of the stopping power at ϱ/αTF ≧ 1 at the levels (0.35 ± 0.05), (0.45 ± 0.05), and (0.52 ± 0.05) keV/ atom for incident beam energies of 100, 200, and 400 keV, respectively.
Third‐Order Elastic Constants and Pressure Derivatives of Second‐Order Elastic Constants of Fluorite‐Structure Crystals
Authors: Shanker J. , Singh J. P. 
Published: July 2007

AbstractAn analysis of interionic potentials is performed in CaF2, SrF2, BaF2, PbF2, Sr(NO3)2, Ba(NO3)2 crystals with fluorite‐structure. Lundqvist's three body interactions and the van der Waals dipole‐dipole interaction along with short‐range overlap repulsive interactions are taken into account in order to evaluate the third order elastic constants and pressure derivatives of second order elastic constants for the crystals under study. The results obtained are compared with those calculated from the shell model and two body potentials and also with experimental values.
Perturbation Expansion for the Asymmetric Anderson Hamiltonian II. General Asymmetry
Authors: Horvatić B. , Zlatic V. 
Published: July 2007

AbstractThe asymmetric single‐orbital Anderson model is studied by the rapidly convergent perturbation method of Yosida and Yamada. Low‐temperature specific heat, resistivity, thermoelectric power, and renormalized position of the virtual bound state are evaluated to the second order in Coulomb correlation for arbitrary asymmetry. The effect of asymmetry on the properties of the model is discussed. It is found that the correlation effects are most pronounced in the case of electron–hole symmetry and are strongly reduced with the increase of asymmetry.
Photosensitive EPR of Ge3+ and Sn3+ in Twinned Cubic Zinc Sulfide
Authors: Backs D. , Freyer H. J. 
Published: July 2007

AbstractGermanium‐and tin‐doped cubic ZnS single crystals are investigated by EPR and optical excitation and quenching spectra of EPR. In the case of tin‐doped cubic ZnS a different g‐factor is observed than for haxagonal ZnS. The hyperfine intersaction with Sn115 in ZnS is observed for the first time. From the excitation and quenching spectra a simple level scheme is proposed to explain the electornic transitions. Charge exchange is obnserved in the quenching process of Ge‐doped ZnS between germanium and iron, and between tin and chromium for tin‐doped ZnS. From this it is concluded that Ge and Sn are incorporated into the host lattice on cation site and in a divalent charge state.
Exciton and Electron‐‐Hole Liquid Luminescence of Germanium in an Electric Field
Authors: Ganser M. , Seelmann‐Eggebert M. , Huebener R. P. 
Published: July 2007

AbstractMeasurements of the exciton and the electrron–hole liquid (EHL) luminescence of optically pumped germanium are reported for the temperature range of 2.1 to 4.2 K in the presence of an electric field. Simultaneously with the luminescence the electrical conductivity behaviour is studied. At an electric field near 3.0 V/cm the EHL luminescence sharply drops to zero. With increasing field the drop of the free‐exciton luminescence is less sharp than that of the EHL luminescence and sets in as soon as the EHL luminescence vanishes. This field dependence together with the conductivity results can be explained by impact ionization of the free excitons. Apparently during this process the EHL acts as a buffer for the free‐exciton system.
Collective Phenomena in Edge Emission of ZnTe and ZnSe Crystals
Authors: Baltramieyunas R. , Kuokshtis E. 
Published: July 2007

AbstractThe radiative recombination of highly excited ZnTe and ZnSe single crystals in their self‐absorption region is studied. The new L‐ and P‐bands are observed in the emission spectra of the crystals under investigation. It is established on the basis of experimental and theoretical analysis of the spontaneous luminescence and optical gain spectra shapes, their dependence upon the excitation intensity and temperature, as well as shallow impurities, that radiative transitions in electronhole drops (EHD) predominate in luminescence at low temperature (4.2 K) in the most pure ZnTe and ZnSe crystals and are responsible for the L‐band. The P‐band caused by radiative processes in dense partly ionized exciton gas appears in the luminescence spectra in the defective crystals or at high temperature. The question is discussed of the competition of the radiative recombination in EHD and in exciton gas, as well as in homogeneous electron‐hole plasma forming near the surface of the crystal or under the thermal splitting of excitons.
Iteration Method in the Theory of Nonhomogeneous Dielectrics
Authors: Fokin A. G. 
Published: July 2007

AbstractThe problem of finding the relationship between an unknown field E and the field Ec, which is the solution of a similar boundary value problem for an auxiliary medium, is solved for an arbitrary (in the sense of the distribution of the nonhomogeneities and their dielectric properties) nonhomogeneous medium of volume V. The Poisson equation for the nonhomogeneous medium corresponds to the integral equation for the field E. Methods of functional analysis are used to show that the solution of the equation can be represented in the form of the Neumann series, which in general satisfies the conditions of uniform convergence. Certain limitations on the dielectric permittivities of the auxiliary medium are derived as sufficient conditions for the convergence of the series.
Level Ordering in II3‐‐V2 Semiconducting Compounds
Authors: Cisowski J. 
Published: July 2007

AbstractThe quasicubic model as well as the known value of the crystal field splitting of Cd3As2 are used to calculate this splitting in other II3–V2 compounds. The ordering of p‐like levels at the Γ‐point is determined and compared with recently available experimental data.
Polariton and Spatial Dispersion Effects in Exciton Spectra of Xenon Cryocrystals
Authors: Fugol I. Ya. , Grigorashchenko O. N. , Savchenko E. V. 
Published: July 2007

AbstractTransmission and luminescence spectra of Xe cryocrystals are studied experimentally in the region of the n = 1, Γ(3/2)‐resonant transition at 5 to 80 K. On the basis of the polariton theory and with allowance for spatial dispersion, the optical characteristics of solid Xe are calculated and show good agreement with experiment. The effects of the Raman scattering of polaritons, two‐phonon process contributions, and the existence of temperature barriers in scattering are discussed.
Properties of Exciton Polaritons Studied in a One‐Dimensional Model
Authors: Balslev I. , Stahl A. 
Published: July 2007

AbstractExciton polaritons are traditionally considered as composite particles formed from bare excitons and photons. In a recently developed alternative approach one starts from polariton theory in configuration space and finds excitons as resonances in the polariton system. The relation between the two methods is explored in the present paper. Using a simplified one‐dimensional model the configuration space system is solved exactly for bulk and halfspace geometry, partly by numerical methods. The solutions are in good agreement with experimental reflection spectra. In order to rederive the results of traditional theory one has to apply aproximations: The “rigid‐exciton approximation” for bulk solutions and the adiabatic approximation for halfspace geometry. The influence of these approximations is discussed.
Transport Properties and Plasma Resonance of Bismuth Selenide Crystals Doped with Cadmium
Authors: Horäk J. , Koudelka L. , Klikorka J. , Šiška L. 
Published: July 2007

AbstractElectrical conductivity, Seebeck coefficient, Hall constant, and plasma resonance frequency are determined for samples of Bi2Se3 crystals, pure and doped with Cd. The concentration of the free carriers is determined from the measured transport parameters and compared with the concentration of cadmium atoms as determined by atomic absorption technique. It is found that each Cd atom built into the crystal lattice removes approximately one conduction electron. On the basis of this finding and using the ideas about the bonding conditions in the lattice, the nature of the point defects brought about by introducing Cd atoms into the Bi2Se3 crystals is describecd. The Cd atoms occupy the sites of Bi atoms, which results in Cd′Bi defects of acceptor nature. Finally, a comparison of the properties of the impurities from the group 2b of the periodic system is made.
Model of Self‐Consistency Simulation in Constructing a Non‐Self‐Consistent MT Potential for Metals
Authors: Stepanyuk V. S. , Evdokimenko O. A. , Katsnelson A. A. , Shpotin I. S. , Yastrebov L. I. 
Published: July 2007

AbstractIt is shown that the use of the Friedel sum rule in constructing the “muffin‐tin” potential for metals can be considered as the procedure of self‐consistency simulation. Energy band structure calculations of V and Cr are made both with the use of the Friedel sum rule and without it. Comparison of the results with the self‐consistent calculations which were made earlier show good agreement when the Friedel sum rule is used. The change of the energy band structure in the process of lattice dilatation is investigated.
Dielectric Relaxation in Polar Liquid Crystals
Authors: Buka A. , Leyvraz F. 
Published: July 2007

AbstractA model is suggested for interpreting the experimental dielectric dispersion data in nematic liquid crystals. The high‐frequency dispersion is observed in both, parallel and perpendicular alignment of substances with only a molecular dipole moment parallel to the long axis of the molecule. In the absence of a perpendicular dipole moment component these high‐frequency absorptions cannot be associated with rotation about the molecular axis. The model is based on Kubo's linear response theory and describes the dipole relaxation processes in frames of rotational diffusion. Results are compared with experimental data obtained on 4‐cyano‐4′‐octylbiphenyl.
Vacancies in α‐Zirconium
Authors: Ong C. K. 
Published: July 2007

AbstractA Lennard‐Jones potential is used to calculate the formation and binding energies for a monovacancy, divacancy, and trivacancy in α‐Zr. Stable divacancy and trivacancy configurations are found. The displacement fields, dipole force tensors, and relaxed volumes of the vacancy clusters are also calculated.
Nonequivalence of De Launay and Clark, Gazis, and Wallis Angular Force Models
Authors: Ramamurthy V. 
Published: July 2007

AbstractThe angular force models of De Launay and Clark, Gazis, and Wallis are analysed by resolving the atomic displacements along three mutually perpendicular directions. It is shown that the CGW model which neglects a two‐body force component perpendicular to the plane of the triangle is not equivalent to the DAF model which neglects the three‐body forces confined to the plane, for any crystal structure and all the earlier claims regarding their equivalence are therefore spurious. The equivalence between the angular force constants of these models, the relations between these and other force constant models as well as the role played by the axially symmetric forces, in the case of b.c.c. and f.c.c. structures are discussed.
Investigation of Transport Coefficients in Semimetals by the Variational Method I. General Solution of the Problem
Authors: Gitsu D. V. , Golban I. M. , Kantser V. G. 
Published: July 2007

AbstractA variational procedure for the solution of the Boltzmann equation with an arbitrary number of variational parameters is developed. In the frame of the method it is possible to carry out the optimization of trial function, as well as to check the convergence of the solution. It is shown that in semimetals the probability matrix of charge carrier scattering on acoustic phonons entering the expression for the collision operator has a non‐diagonal form in the coordinate system of the effective mass tensor. General expressions are obtained for the transport coefficients allowing to determine their numerical values.
Interband Magnetoreflectivity at Pb1−xSnxSe Single Crystals
Authors: Bange K. , Liebegall A. , Lorentz B. 
Published: July 2007

AbstractFor Pb1‐xSnxSe single crystals with x = 0.035, 0.045, and 0.070 the interband magnetooptical reflectivity (IMOR) is studied using a CO2 laser emitting between 10.1 and 10.7 μm and variable magnetic fields up to 5.5 T. The spectra are obtained with the samples in Faraday configuration for left circularly, right circularly, and linearly polarized (lcp, rcp, and lp) radiation. The experimentally determined transition energies lead to band parameters calculated with a six‐band model, which are discussed in terms of their dependence on alloy composition.
Bulk Photovoltaic Effect in a Ferroelectric Crystal A Model Calculation
Authors: Presting H. , Von Baltz R. 
Published: July 2007

AbstractA numerical investigation of the bulk photovoltaic tensor for a ferroelectric crystal is presented. The studies are based on a simple two‐dimensional LCAO model which preferably can be treated analytically. In contrast to previous studies, however, the complete band structure and wave vector dependence of the transition matrix elements are taken into account. This paper also reports the first numerical application of the R‐vector concept which is recently developed for the intrinsic bulk photovoltaic effect.
EPR Investigation of Manganese–Boron Pairs in Silicon
Authors: Kreissl J. , Gehlhoff W. 
Published: July 2007

AbstractAfter manganese doping of low‐resistivity B‐doped p‐silicon an EPR centre is detected, which could be identified in accordance with Ludwig and Woodbury as a manganese‐boron pair, where a interstitially incorporated Mn2+ ion is located in the immediate vicinity of a B− ion on a substitutional site. It is shown, that compared to the main direction H ∥ C3 and H τ C3 the much more complex spectra observed for arbitrary directions of the magnetic field are caused by the simultaneous appearance of “allowed” and “forbidden” hyperfine transitions owing to the comparable magnitudes of the Zeeman splitting and fine structure splitting in the X‐band. Additionally a weak dependence of the magnitude of the local trigonal crystal‐field distortion at the manganese site on the associated boron isotope 10B/11B is proved (isotope effect in the fine structure).
Role of Zero‐Point Motion and Three‐Body Effects in the Study of Crystal Properties of Rare Gas Solids
Authors: Singh R. K. , Neb D. K. 
Published: July 2007

AbstractThe role of zero‐point motion and three‐body interactions (TBI) is investigated in describing the numerous crystal properties of rare gas solids (RGS). The model used is made less parametric in nature by incorporating the effect of TBI via overlap integrals evaluated by Hafemeister. Remarkably good agreement is achieved between theoretical and experimental results on cohesive, harmonic, and anharmonic elastic and thermophysical properties of RGS.
Ion Implantation in Alkaline Earth Oxides
Authors: Henderson B. , Garrison A. H. 
Published: July 2007

AbstractSpectroscopic investigations of defects are made in alkaline earth oxides implanted with 400 keV Li+ or Na+ ions. Detailed comparisons of ESR, optical absorption, and luminescence spectra confirm that the predominant point defect is the F+ centre. Smaller concentrations of F2 and F centres are also produced. V− centres and isolated anion vacancy centres are not produced by irradiation. Annealing studies demonstrate that colloid centres grow during annealing above 500 K.
Absorption and Stress‐Induced Linear Dichroism of Pb++ Centres in KCl and RbCl
Authors: Schmitt K. 
Published: July 2007

AbstractThe optical absorption and the stress‐induced linear dichroism (SLD) of Pb++‐centres in KCl and RbCl are investigated in the temperature range 4 to 200 K. Using moments analysis the energy parameters of the systems, the effective electron‐phonon‐coupling constants of the |A> state, and the effective frequencies of the A1g, E2g, and T2g interaction modes are determined. The temperature dependence of the B‐band and the splitting of the C‐band give additional information about the dynamical properties of the systems. The results imply that in either case the electronlattice interactions of the 3T1u state and of the 1T1u state are of comparable strength.
Anharmonic Coupling of Phonon Modes in Mixed ZnxCd1−xSe Crystals
Authors: Valakh M. Ya. , Lisitsa M. P. , Pekar G. S. , Polysskii G. N. , Sidorenko V. I. , Yaremko A. M. 
Published: July 2007

AbstractThe vibrational properties of ZnxCd1–xSe phonons are studied using Raman scattering. The change of the LO‐phonon spectrum versus crystal composition is found to be of the one‐mode type. The TO‐phonon behaviour is much more complicated. It exhibits rather anomalous features in the line shape and TO‐mode frequency versus crystal composition as well as temperature. The above phenomena are interpreted in terms of the anharmonic coupling between TO‐mode and two‐ phonon states. This coupling is well described by the theory developed.
Analysis of Crystal Binding and Grüneisen Parameter in Cesium Halides, silver Halides, and Alkaline Earth Oxides
Authors: Shanker J. , Singh K. 
Published: July 2007

AbstractAn analysis of the crystal binding energies and the Grüneisen parameter γ is performed in CsCl, CsBr, CsI, AgCl, AgBr, MgO, CaO, SrO, and BaO crystals. Values of cohesive energy, the Grüneisen parameter, and its volume derivative are calculated for all the crystals under study. Different theories of γ are used and compared with each other. Various potential functions for the repulsive energy are used in the calculations. The van der Waals interactions are also taken into account. The potential parameters for the repulsive energy are determined using input data on interionic separation and bulk modulus. The Born‐Landé inverse power and the Born‐Mayer exponential forms are adopted for repulsive interactions upto second neighbours. The results obtained are compared with available experimental data.
Low temperature conductivity and optical transitions of a two‐dimensional disordered semiconductor under weak localization conditions
Authors: Bonch‐Bruevich V. L. , Nguyet To Thi Bich 
Published: July 2007

AbstractTwo problems are considered of the theory of two‐dimensional disordered semiconductors. The first one is that of a temperature dependence of the static conductivity when the Fermi level lies in the weak localization region. The second one concerns the frequency dependence of the light absorption coefficient due to electron transitions between the strongly (exponentially) and weakly localized states. It is shown that the latter experiments might reveal the form of the density of states in a weakly localization region.