bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of intrinsic recombination at zero temperature in small gap semiconductors
Authors: Mocker M. , Beiler Marion 
Published: July 2007

AbstractA theory of intrinsic recombination at zero temperature is developed. Numerical results in a wide range of excitation and doping concentrations are given for a model adapted to PbS0.1Se0.9. In order that first‐order Auger recombination is possible a minimum value of majority carrier concentration has to be reached. Consequently, a finite small signal lifetime only exists if doping concentration ND > N D min, where for PbS0.1Se0.9 N D min ≈ 4.5 × 1018 cm−3 in case of parabolic model and N Dmin ≈ 9 × 1019 cm−3 in case of Kane model of band structure. Radiative recombination rate only depends on minority carrier concentration p. At strong excitation the radiative lifetime behaves like p−213 in parabolic and like p−113 in Kane band approximation. Quantum efficiency η of radiative processes in dependence on ND decreases steplike near N D ≈ N D min.
Effect of three‐body forces on thermophysical and anharmonic properties of rare gas solid mixtures
Authors: Singh R. K. , Neb D. K. , Sanyal S. P. 
Published: July 2007

AbstractThe effects of three‐body forces on the thermophysical and anharmonic properties of rare gas solid (RGS) mixtures are investigated using the virtual crystal approximation and an interatomic potential consisting of the long‐range van der Waals dipole–dipole interaction and three‐body forces, the short‐range Born‐Mayer type overlap repulsion, and the zero‐point energy. The agreement between experimental and our theoretical results of various properties of the host RGS is, generally, better than obtained by most earlier workers. The results on RGS mixtures follow systematic trends identical to those of diatomic solid mixtures but reliance in them will be deferred until the report of the corresponding measured data.
Phonon transmission theory of heat transfer through solid–gas interfaces
Authors: Dharmadurai G. 
Published: July 2007

AbstractThe heat flow is investigated from a hot solid into a gaseous medium using the phonon transmission theory. This basic approach correctly predicts the essential features of the temperature jump occurring at solid–gas interfaces during heat flow across the boundary and the predictions agree well with recent measurements of heat transfer between microspheres of UO2 in helium and nitrogen atmospheres. The results suggest that the medium–medium acoustic mismatch dominates the heat transfer through these interfaces.
Perturbation‐theoretical model calculation of the lattice mechanics of low polarisability ionic crystals
Authors: Bose D. , Ghosh A. , Basu A. N. 
Published: July 2007

AbstractStarting from the Hartree‐Fock wave functions of free ions different lattice mechanical properties of a low‐polarisability ionic solid, namely, the RbF crystal are calculated within the framework of the perturbation‐theoretical‐model approach of ionic solids developed by Basu and Sengupta. In a recent investigation it is shown that the dipolar polarisation in an ionic solid may be additively decomposed into three parts, two short range polarisation effects and a long range one apart from the displacement polarisation. From an analysis of the Szigeti relations it is found that both the short range polarisation effects in the low polarisability ionic crystals are small compared to those in high polarisability crystals. This fact leads to a major simplification in calculation for this group of solids. The overall agreement obtained broadly justifies the approximations. Since no crystal property is used to obtain the parameters the discrepancies clearly indicate the regions where the omitted interactions are important. Finally a critical analysis of the results is presented and the difficulties of the existing phenomenological models for these solids are also discussed.
Influence of the orientation of anisotropic impurity–vacancy complexes upon dislocation charging in NaCl crystals
Authors: Andronikashvili E. L. , Galustashvili M. V. 
Published: July 2007

AbstractElectrical effects are investigated observed during charged dislocation motion in NaCl crystals containing impurity–vacancy dipoles oriented in an electric field (E = 12 kV/cm). It is shown that the efficiency of dislocation charging, i.e. vacancy absorption from the dipole by the dislocation, depends on the mutual orientation of the dipole and the moving dislocation. The data obtained can be explained within a model taking into account both the elastic dislocation–dipole interaction and the electrostatic interaction of the dipole components of opposite charges.
Optical phonons and structure of TlGaS2, TlGaSe2, and TlInS2 layer single crystals
Authors: Gasanly N. M. , Goncharov A. F. , Melnik N. N. , Ragimov A. S. , Tagirov V. I. 
Published: July 2007

AbstractThe polarization properties of bands in Raman scattering and IR reflection spectra are studied experimentally in TlGaS2, TlGaSe2, and TlInS2 layer single crystals and in solid solutions based on them. Additionally the angular dependence of IR‐active modes on the angle between the phonon wave vector and the direction of the optical axis c of single crystals is investigated. It is shown that the observed phonon spectra can be interpreted on the basis of a primitive cell which contains two tetragonal‐symmetry layers bonded to each other by an inversion operation. Bands corresponding to cells with a mixed composition are observed in the Raman spectra of the solid solutions.
Parametric generation of submillimeter radiation in semiconductors in the field of a bichromatic pulse
Authors: Avetissian S. K. , Kazarian E. M. , Melikian A. O. , Minasian H. R. 
Published: July 2007

AbstractThe self‐consistent problem of the interaction of three collinear laser pulses with frequencies ω1, ω2, ω3, propagating in a semiconductor, is discussed. The quasi‐energy spectrum of the semiconductor is determined for the excitation frequencies ω1, ω2 ⪆ Eg/ħ, where Eg is the forbidden band width, and ω3 = ω2 – ω1 ≪ Eg/ħ. The problem of resonance parametric generation of the difference frequency ω3 is considered on the basis of an exact expression for the semiconductor polarization. The possibility of submillimeter radiation generation in semiconductors with Eg ≈ ≈ 0.1 eV is shown. The efficiency of a conversion of the corresponding process is determined.
Quadrupole splitting of hydrogen‐like atom levels in crystals
Authors: Baryshevskii V. G. , Kuten S. A. , Rapoport V. I. 
Published: July 2007

AbstractThe theory of the behaviour of a hydrogen‐like impurity atom with quadrupole moment in a crystal is presented. It is shown that available EPR data on atomic hydrogen trapped in crystalline SiO2 testify to the fact that it has an electric quadrupole moment. Another proof is presented of atomic hydrogen and muonium (a light isotope of hydrogen) trapped at the same sites in the α‐quartz lattice.
Phonon lifetime and thermal conductivity in amorphous solids
Authors: Handrich K. 
Published: July 2007

AbstractAfter a short discussion of the static structure factor S(κ) in the small angle region and the low‐temperature thermal conductivity χ(T) of amorphous solids, a perturbation theory is developed, which yields the phonon lifetime τκ and the thermal conductivity χ of a weakly and randomly inhomogeneous solid. It is shown that the strong increase of S(κ) for κ ⪅ 10−2 Å−1 leads to τκ ∽ κ and χ ∽ T2 for T ⪅ 1 K. From S(κ) ≈ const. for κ ⪆ 10−2 Å−1 it follows τκ ∽ κ4 (Rayleigh scattering). Thus phonons with wave vectors κ ⪆ 10−2 Å−1 will be strongly scattered and will not contribute to the thermal conductivity. This is the reason for the plateau of χ for T ⪆ 1 K.
Spectrum of magnetization oscillations in a uniaxial ferromagnetic plate
Authors: Bespyatykh Yu. I. , Dikshtein I. E. , Meriakri S. V. , Tarasenko V. V. 
Published: July 2007

AbstractA theoretical investigation is made for the ground statè of a ferromagnetic plate in the vicinity of the Curie temperature in a normal magnetic field. It is shown that there can exist either a uniform magnetic state, a strip domain structure, or a hexagonal domain lattice depending on the temperature and the magnetic field. The spectrum of magnetization oscillations in each of the possible states is calculated and the stability regions of different phases are determined. The results are generalized for orientational phase transitions in the uniaxial ferromagnetic plate in a oblique magnetic field.
The influence of parameter nonuniformity on the two‐dimensional einstein relation in periodic and non‐periodic semiconductor structures
Authors: Tjapkin D. , Milanović V. 
Published: July 2007

AbstractTaking into account the fact that the effective mass of carriers is spatial dependent, the expression for the Einstein relation (the diffusion coefficient to mobility ratio) are derived for the two‐dimensional electron gas. The derived expressions are general and do not assume exclusively the parabolic dependence of the carrier energy on the wave vector, as well as the case of the quantum limit. The numerical results are given for GaAs‐AlxGa1−xAs superlattice structure assuming that the dependence of the potential energy is rectangular. The maximum and the minimum are found for D/μ versus Ns which could be explained as a consequence of the spatial dependence of effective mass.
Ionic conductivity of BaFCl
Authors: Somaiah K. , Hari Babu V. 
Published: July 2007

AbstractThe ionic conductivity of undoped and doped BaFCl single crystals is measured. In BaFCl, the measurements are performed parallel and perpendicular to the crystallographic c‐axis. Incorporation of monovalent impurities (Tl, Na) enhances the conductivity while it decreases by doping with trivalent impurities (Gd). The results indicate that BaFCl has anionic conduction via halide ion vacancies and that the thermally generated lattice defects are of Schottky type. The probable mechanism for the conduction process in these crystals is discussed on the basis of structural considerations of the unit cell.
De‐correlation technique for separation of drude parameters from wavelength modulation spectroscopy data
Authors: Burd M. , Stearns R. , Braunstein R. 
Published: July 2007

AbstractSeparation of bound‐ and free‐electron contributionsto the dielectric function is necessary for an accurate analysis of interband transitions. A technique for doing this separation which does not require low energy data is presented. The technique makes use of the fact that the functions which describe the contributions of each part are sufficiently uncorrelated, allowing the construction of a correlation function which uses the Drude effective mass and Drude relaxation time as adjustable parameters. The technique is shown to properly separate a test function and to yield reasonable results from experimental data.
Optical properties of polaritons in thin crystal films
Authors: Myasnikov V. N. , Marisova S. V. , Lipovchenko A. N. 
Published: July 2007

AbstractThe dispersion relation for polaritons in a crystal slab of an arbitrary thickness is derived by the quantum Green function method. The equation is reduced to the classical electrodynamics form with an effective dielectric function depending on the crystal thickness. The energy and the radiation damping of polariton modes in thin anthracene crystals are calculated and compared with the experimental values based on the studies of low‐temperature luminescence and refractive index dispersion.
Inverse dielectric function for a semi‐infinite solid
Authors: Bechstedt F. , Enderlein R. , Reichardt D. 
Published: July 2007

AbstractAn old problem is addressed being the description of the dielectric response of electrons near the surface of an infinite half space to perturbing potentials and external charges. Taking into account spatial dispersion, expressions are derived for the screened potential and the inverse dielectric function within the approximation of specular electron reflection. The expressions generalize former results in a way that spatial symmetries of the problem are properly reflected. The boundary conditions are shown to follow from the definition of the screened potential. The inverse dielectric function obtained in the treatment fulfils the orthogonality relation to the dielectric function and the f‐sum rule.
EPR transitions for ions with S = 3/2 in the presence of small distortions of the cubic crystal field
Authors: Harris E. A. , Tucker J. W. 
Published: July 2007

AbstractThe effect of small distortions from cubic symmetry on the EPR line positions for S = 3/2 is calculated using a perturbative approach for the case where there is a well resolved hyperfine splitting. It is found that for the Ms = −1/2 to Ms = +1/2 transitions, where the line shifts due to these distortions are small compared to the linewidths, the centre of gravity of each line show a pseudo‐cubic angular dependence −9/5 (udβH + Udm) [1 – 5(α21α22 + α22α23 + α23α21)] with ud/Ud = −3g/(11A), and αi the direction cosines of the magnetic field with respect to the cubic axes.
Electronic properties of dilute copper alloys I. theory
Authors: Mertig I. , Mrosan E. , Zeller R. , Dederichs P. H. , Ziesche P. 
Published: July 2007

AbstractThe electronic properties of 4d transition metal impurities and sp impurities of the third, fourth, and fifth rows of the periodic table in a Cu host are calculated self‐consistently. The impurity is embedded in the perfect crystal environment and described by a single perturbed muffin‐tin potential in the KKR‐Green function scheme. The influence of the impurities on the de Haasvan Alphen effect (Dingle temperatures and changes in areas of the Fermi surface) and the residual resistivity are discussed. For the residual resistivity the linearized Boltzmann equation is solved taking into account the full anisotropic band structure of the host.
Quantum tunneling between inequivalent locations small polaron motion
Authors: Riseborough P. S. 
Published: July 2007

AbstractThe rate at which an electron transfers between bound states with differing energies as well as different spatial locations is examined. The coupling to a phonon bath not only serves to provide or dissipate the excess electronic energies involved in the transition, but also dephases the quantum coherence thereby dramatically increasing the time or Poincare reccurence of the system. At high temperatures, the description of a particle at a site is reasonable, and the inter‐site transition rate is calculated. At lower temperatures, when thermally activated phonons are scarce, the description in terms of bonding and antibonding states is more appropriate. For this regime, the rate for transfer between the bonding and antibonding states is calculated.
Impurity band conduction in single crystals of p‐type GaSb
Authors: Chaudhuri K. D. , Malik Anita , Kukreti Sunita , Mathur P. C. 
Published: July 2007

AbstractMeasurements of the Hall coefficient, dc conductivity at low and moderate electric fields, and magnetoresistance are made on heavily doped and compensated GaSb single crystals from liquid helium to room temperature range. The electrical transport in the low temperature region up to about 50 K is found to be mainly due to impurity band conduction by thermally activated hopping. The population of carriers in the impurity band and valence band is calculated from the Hall effect and low field conductivity data. The values of the average hopping distance in the impurity band at various temperatures are calculated from the observed data on high field dc conductivity. The magnetoresistance in the cryogenic temperature range is found to be negative while for temperatures between 40 and 150 K the magnetoresistance though positive shows significant deviation from the square law behaviour. For temperatures above 150 K, ΔQ/Q is found to vary with magnetic field B in accordance with the square law (ΔQ/Q ∼ B2) which is the normal behaviour of free charge carriers.
On the Magnetic Structure of the Intermetallic Compounds Gd2Al And Gd2Au
Authors: Brédimas V. , Papatriantafyllou K. , Gamari‐Seale H. 
Published: July 2007

AbstractUsing the molecular field model to non Bravais lattices the following results are obtained: The sub‐lattices of Gd for the compound Gd2Au in the first ordered state below the paramagnetic state order ferromagnetically while in the Gd2Al compound they possess a helicoidal spin structure. In the ground state, Gd2Au is ferromagnetic and Gd2Al is antiferromagnetic when a quite large number of neighbours is included in the calculation and for a propagation vector k = 0 (ferromagnetic sublattices).
The Microscopic Theory of the Gyration and Electrogyration in Dielectric Crystals
Authors: Stasyuk I. V. , Kotsur S. S. 
Published: July 2007

AbstractIn the framework of a microscopic model general expressions for the components of the gyration and electrogyration tensors for dielectric crystals are obtained. The lattice contributions to the effects and contributions from single ions (or ionic complexes) are separated. The temperature and frequency dependences of the components of the calculated tensors are analyzed.
Electronic Properties of Dilute Copper Alloys II. Residual Resistivity
Authors: Mertig I. , Mrosan E. , Zeller R. , Dederichs P. H. 
Published: July 2007

AbstractThe residual resistivity of 4d transition metal impurities and of sp impurities of the third, fourth, and fifth rows of the periodic system in a Cu host is calculated. The linearized Boltzmann equation is solved using the degenerate kernel technique taking into account the full anisotropic band structure of the host. The results are compared with experimental information and some other theoretical treatments.
Knight Shifts of Protons in Some Rare‐Earth Dihydrides
Authors: Żogal O. J. 
Published: July 2007

AbstractProton NMR Knight shifts are measured in the paramagnetic state of RH2 (where R = Pr, Nd, Sm, Gd, and Tb). The data are interpreted in terms of the effective hyperfine field at the proton site, being equal to −16.7 × 104 A/m for the Pr, Nd, Gd, and Tb dihydrides and −7.96 × 104 A/m for SmH2. The temperature dependence of the magnetic susceptibility in SmH2 is also measured. The anomaly observed at 9 K is attributed to antiferromagnetic ordering. Analysis of the susceptibility data indicates that SmH2 is the Sm3+ compound.
Resonant Brillouin Scattering in HgI2 Investigated by Acoustic Domain Injection Method
Authors: Itoh Y. , Hamaguchi C. 
Published: July 2007

AbstractResonant Brillouin scattering by the transverse acoustic phonons is investigated for the first time in red HgI2 single crystal at room temperature by using the acoustic domain injection method. The measured results in the spectral region 579 to 800 nm show a non‐dispersive feature at the longer wavelength region and a decrease in the region very close to the fundamental absorption edge. The analysis based on the resonant Brillouin scattering theory and piezobirefringence theory shows excellent agreement with the present observation and predicts a resonant cancellation of the scattering cross section at 574 nm.
Application of CPA to the Magnon Hamiltonian
Authors: Jezierski A. 
Published: July 2007

AbstractThe coherent potential approximation is applied to the effective magnon Hamiltonian. The magnon creation operator is defined in this method for the average medium. The average exchange spin wave stiffness constant is calculated and the expression is given for the magnon scattering contribution to the stiffness constant. The method of calculation of the magnon energy in disordered alloys presented in this paper gives the same result as the method based on the dynamical transverse susceptibility.
The Dynamical Electron–Phonon Mode Coupling in Jahn‐Teller Crystals with Antiferroelastic Ordering
Authors: Kaplan M. D. 
Published: July 2007

AbstractThe dispersion equation for the coupled electron‐phonon modes, active in the antiferrodistortion ferroelectric phase transition, is obtained by the Green function method. It is shown, that in this case the odd (at T > Tc) quasielectronic branch is the soft mode, which gives a principal contribution to the dielectric anomalies of the crystal. The acoustic property anomalies of the system are due to the interaction of the acoustic mode with the even electronic mode, which is also soft, but is non‐vanishing at T = Tc. The characteristics of the dynamical coupling of the odd electronic mode with the acoustic mode are discussed in the long wave approximation.
On the Electrical Conductivity of Disordered Alloys in the Muffin‐Tin Model
Authors: Schwartz L. , Paja A. 
Published: July 2007

AbstractA formula for the electrical conductivity of a disordered substitutional binary alloy in the muffintin model is given. The non‐vanishing vertex correction gives rise to an additional term. A simple expression for the transport relaxation time is also obtained.
Model Potential Calculation of Phonon Dispersion in Tb and Ho
Authors: Upadhyaya J. C. , Sharma M. L. 
Published: July 2007

AbstractThe nonlocality of the rare earth metal model potential (REMMP) of Upadhyaya and Animalu is considered in the full modified scheme of Eschrig and Wonn to study the lattice dynamics of Tb and Ho. The computed phonon dispersion curves are raised by 10 to 15% when compared to those of the former authors. Next a parameter is suitably adjusted in order to have a reasonable fit with the experimental data. The scheme of Eschrig and Wonn considers only the first order E‐ and (k q)‐dependent terms in the Taylor expansion of the form factor. In the present work the expansion is truncated at the second order and an expression for the energy wave number characteristic, containing additional terms corresponding to E‐, (k q)‐ and mixed dependence, is deduced. When the phonon frequencies of Tb are calculated by including the second order terms, a substantial effect is found. The calculation of phonon frequencies, using nonlocal parameters evaluated from the basic data, is suggested.
The Internal Soft‐Mode Phase Transition in Solid Biphenyl
Authors: Plakida N. M. , Belushkin A. V. , Natkaniec I. , Wasiutyńki T. 
Published: July 2007

AbstractThe phonon dispersion curves in solid biphenyl are calculated. It is shown that the commensurate‐incommensurate phase transition is induced by mixing of anharmonic molecular torsion and acoustic phonons. The parameters of the anharmonic potential for torsion vibrations and temperature dependence of the soft mode are obtained.
Some Extensions of the Shell Model of Ionic Crystals
Authors: Regiński K. 
Published: July 2007

AbstractA model of an ionic crystal is constructed ab initio in terms of moving charged particles interacting mutually with an electromagnetic field. On the basis of the model the equations of motion of the crystal are derived by means of the Lagrangian formalism. Special attention is given to a precise description of interactions between polarizable ions and the electromagnetic field. Retardation of electromagnetic interactions as well as the existence of an external electromagnetic field are taken into account. The system of equations obtained seems to be convenient for an analysis of electromagneto‐optical processes in ionic crystals.
A Method for the Evaluation of Dielectric Relaxation Parameters in Electronic Excited State
Authors: Prakash J. , Rahul  
Published: July 2007

AbstractA method is suggested to evaluate the dielectric relaxation parameters of impurity‐vacancy dipoles in the electronic excited state (ees). The value of the maximum increase observed during the photo‐induced polarization measurements helps in evaluating the dielectric relaxation parameters in ees. Relevant expressions are developed and discussed. The activation energy and fundamental relaxation time in ees in KI:S− − are found to be smaller than their corresponding values in the electronic ground state (egs), whereas the activation energy in ees in KI:Se− − is found to be greater than that observed in egs. In both these cases the product of activation energy and fundamental relaxation time in ees is found to be less than its corresponding value in egs.