bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Grand Partition Function in Defect Statistics
Authors: Landsberg P. T. , Canagaratna S. G. 
Published: July 2007

AbstractIt is explained how the grand partition function method can be used to discuss a) simple defects statistics in which one transition takes place; b) defect statistics in which two transitions take place (Frenkel or Schottky defects); c) more complex statistics. The latter is illustrated by a treatment of a mixture of Schottky and Frenkel defects, not previously discussed in generality.
Dislocations in AIIBVI and AIIIBV Piezoelectric Crystals
Authors: Smirnova I. S. 
Published: July 2007

AbstractThe problem is considered of the distribution of fields produced by dislocations in piezocrystals. The behaviour of the fields is analyzed for all possible dislocations available in b.c.c. crystals (in particular, with the sphalerite lattice) and in crystals with wurtzite lattice (existence of the radial and tangential component E; initiation of polarization vortexes). A considerable reduction in the symmetry of elastic stress fields is revealed for mixed dislocations in b.c.c. crystals.
Extended X‐Ray Absorption Fine Structure in RAl2Ga2 Intermetallies
Authors: Hatwar T. K. , Padalia B. D. , Ghatikar M. N. , Chopra D. R. 
Published: July 2007

AbstractThe near‐edge structure (NES) and the extended X‐ray absorption fine structure (EXAFS) associated with the K‐absorption edge of Ga and L3‐edges of the rare earths (R) (where R  La, Ce, Pr, Nd, Eu, and Yb) are studied in RAl2Ga2 intermetallics using a 600 mm curved crystal spectrograph. The results obtained are discussed in the light of the recent point scattering theory of EXAFS proposed by Lytle, Sayers, and Stern. The EXAFS data are used to obtain the nearneighbour distances in these newly synthesized compounds.
Le spectre de RPE de l'ion Mn2+ dans le tartrate de cadmium (CdC4H4O6 · 5 H2O)
Authors: Korkmaz M. , Aktaş B. , Dupont M. 
Published: July 2007

AbstractNous avons étudié, à température ambiante, le spectre de RPE de l'ion Mn2+ dans un monocristal de CdC4H4O6 · 5 H2O préparé par diffusion. L'ion Mn2+ entre dans le réseau cristallin comme substituant de Cd2+. Les sites de l'ion “impureté” ne sont pas équivalents vis à vis de la symétrie, mais sont magnétiquement équivalents.
Electrical Resistivity of Amorphous SnMn
Authors: Korn D. 
Published: July 2007

AbstractAmorphous alloys of SnMn are produced by quench condensation from the vapour phase onto a substrate held at 5 K. The Mn concentration of the alloys varies between 5 and 60 at%. The electrical resistivity is measured in situ in the temperature range 1.8 to 390 K. The electrical resistivity of all amorphous SnMn alloys increases with decreasing temperature without approaching a constant value at low temperature. To explain the almost constant negative temperature coefficient the assumption is made that in amorphous Sn the orbital angular momenta of the p‐electron interact via spin‐orbit coupling with the Mn ion spin.
Cohesive Properties of Ge, Si, and Diamond Calculated with Minimum Basis Sets
Authors: Holland B. , Greenside H. S. , Schlüter M. 
Published: July 2007

AbstractAb initio calculations are presented of the cohesive properties of Ge, Si, and diamond. Electron‐electron interactions are treated within the local density functional approximation and electronion interactions are described by norm‐conserving pseudopotentials. The wave functions are expanded in local Gaussian orbitals. Acceptable results for equilibrium lattice constant, bulk modulus, and cohesive energy are obtained with few (eight to twelve) Gaussian functions per atom. The results, which are comparable to converged plane wave or local orbital calculations suggest the feasibility of studies of cohesive properties of systems with large numbers of atoms.
The Role of Surface Dislocations in the Continuum Theory of Lattice Defects
Authors: Marcinkowski M. J. 
Published: July 2007

AbstractThe close relationship between the concept of surface dislocations and the continuum theory of lattice defects is clearly demonstrated. In fact, it is shown that without the incorporation of surface dislocations into the classical continuum theories, it is not possible to obtain a complete and self‐consistent understanding of elasto‐plastic bending, grain boundary structure, and the behavior of deformed finite bodies in general.
Decay Kinetics and Polarization of the Ax Emission of KI:In Crystal
Authors: Nagirnyi V. , Soovik T. , Zazubovich S. 
Published: July 2007

AbstractThe decay kinetics and polarization of the AX emission are investigated for In centres in KI:In at 0.35 to 80 K. The parameters of the relaxed AX state are determined. Good agreement is obtained between the experimental results and theory, which suggests a strong interaction of impurity optical electrons with non‐totally symmetric vibrations of the crystal lattice.
Ideal Vacancy States in Si. A Study of the Empirical Tight‐Binding Method
Authors: Tuncay C. , Tomak M. 
Published: July 2007

AbstractA series of calculations is performed to determine the sensitivity of ideal vacancy‐induced deep levels on the empirical tight‐binding parameters. A new parameter set is proposed for Si which yields a somewhat better band structure. The vacancy‐induced bound states and resonances are found to depend on the parameters rather sensitively while the band structures do not show this sensitivity.
The Thermoelectric Power of p‐Ge at Low Temperatures
Authors: Kaden E. , Günter H.‐L. 
Published: July 2007

AbstractThe thermoelectric power of lightly doped p‐Ge is measured in the temperature range of 5 to 300 K for the investigation of phonon scattering. The application of a simple theoretical model requires some knowledge of the dominant carrier scattering processes obtained by measurements of electrical conductivity and Hall effect. In terms of that model, the temperature dependence of the phonon drag part of the thermoelectric power can be attributed to only two phonon scattering processes: phonon‐phonon scattering at higher temperatures and phonon‐boundary scattering at lower temperatures. The constant phonon relaxation time of boundary scattering and its dependence on sample diameter has been observed at temperatures below 10 K.
Thermal Energy and the Equation of State for Alkali Halide Crystals
Authors: Bhende W. N. , Bakhshi P. S. , Shanker J. 
Published: July 2007

AbstractThe effect is investigated of recently calculated van der Waals potentials and new ultrasonic elastic data on thermal energy, crystal binding energy, and compressibility of alkali halide crystals within the framework of Hildebrand and Mie‐Grüneisen equations of state. Recent experimental data on the compression of LiF crystal are compared with the results calculated in the present work. It is found that the Hildebrand equation of state using an exponential form alongwith the vdW interactions yields better agreement with experimental data than those obtained from other potential models based on an inverse power form or the Mie‐Grüneisen equation of state.
Self‐Consistent Field Approximation for the Vibrational Spectra of Quaternary Alloys
Authors: Kleinert P. 
Published: July 2007

AbstractA mean‐field approach is applied to the lattice dynamics of quaternary alloys. Specific results are obtained for the quaternaries AlxGa1−xAs1−yPy and GaxIn1−xP1−yAsy. Calculations are restricted to a mass‐disordered linear chain model. For the end‐member components the approach reproduces the results of the coherent‐potential approximation (CPA). The cluster density of states of eight atoms embedded in the mean‐field effective medium is compared with the numerical spectrum obtained for a 20000‐atom random chain by using the negative eigenvalue theorem. The predictions of the calculated mean‐field dielectric susceptibility agree at least qualitatively with experimental results. With some qualifications the approach can explain the change of mode behaviour within the composition range, as it is expected to occur in some III–V quaternary alloys.
Electric Field‐Induced First Order Raman Scattering in Alkali Halides
Authors: Dick B. G. 
Published: July 2007

AbstractA shell model calculation suggests that, for electric fields of 2.5 × 105 V/cm, field‐induced first order Raman scattering cross‐sections may be only about two to three orders of magnitude smaller than those for second order Raman scattering.
Triplet Excitons in Non‐Resonant Molecular Pairs. Saturation Effects in Electron Spin Resonance
Authors: Reineker P. , Köhler J. , Schmid U. 
Published: July 2007

AbstractFor triplet excitons in non‐resonant pairs of differently oriented molecules the saturation of the ESR lineshape is investigated. The model takes into account the coherent exciton motion, an inhomogeneous distribution of electronic excitation energies, Zeeman and fine‐structure terms, and the microscopic interaction with phonons.
Tunneling from Deep Levels of l–c Type in Electric Fields
Authors: Köster H. , Kurnosova O. V. , Yassievich I. N. 
Published: July 2007

AbstractThe tunneling probabilities from deep levels of l–c type to the conduction band (for electrons) and to the valence band (for holes) of semiconductors are derived. In connection with these results an expression is calculated for the valence‐to‐conduction‐band tunneling current via deep levels in the forbidden band. Moreover it is shown that the effective tunneling energy differs from the real defect energy within the gap. This defect energy correction has direct consequences for the analysis of corresponding experimental investigations.
Structure and Bonding in Cubic IV–VI Crystals. IV. Evidence for Covalent Bonding in the IV–VI Family from the Extended Mulliken Scheme
Authors: Enders P. 
Published: July 2007

AbstractThe investigation of IV–VI compounds within the framework of the Mulliken scheme for atomic electronegativities extended recently by Watson et al. gives support for a predominantly covalent bonding character in these materials from atomic properties, too. Here, mono‐ and dichalcogenides and ‐oxides as well as solid solutions are considered.
The Rǒle of Two‐Level Systems in Amorphous Metallic Alloys. II. Micromagnetic Theory of Magnetic After‐Effects in Amorphous Ferromagnets
Authors: Kronmüller H. 
Published: July 2007

AbstractThe magnetic after‐effect in amorphous alloys is attributed to the reorientation of mobile atom pairs in regions of reduced mass density. It is shown that the model of two‐level systems (TLSs) gives an appropriate description of the thermodynamic and micromagnetic properties of the magnetic after‐effects. “Reversible” and “irreversible” relaxation processes are attributed to the annealing of mobile atom pairs and to changes of the energy splitting parameters of the TLSs.
Electronic Energy Bands of Pr under Pressure
Authors: De S. , Bose I. , Chatterjee S. 
Published: July 2007

AbstractPraseodymium has a number of interesting phase transitions under pressure. Band structure calculations are performed for Pr in both, the low and high pressure region using the composite wave variational version of the APW method. Based on the results obtained, some conjecture is made to the nature of the most prominent transition.
Screening of the Spin–Orbit Exciton by the Electron–Hole Liquid in Germanium
Authors: Asnin V. M. , Stepanov V. I. , Zimmermann R. , Rösler M. 
Published: July 2007

AbstractAbsorption and modulated transmission in the spectral region of spin‐orbit transitions in Ge are measured and compared with calculations which take into account excitonic effects and their changes under high excitation. Measurements at high magnetic fields corroborate the findings.
Dissociation‐Accompanied Raman Scattering by Davydov Solitons
Authors: Eremko A. A. , Gaididei Yu. B. , Vakhnenko A. A. 
Published: July 2007

AbstractA theoretical study is made of the Raman scattering by a molecular chain in the state of the soliton excitation accompanied by a soliton dissociation. The differential cross‐section of such a scattering is calculated.
Magnon Drops in One‐Dimensional Ferromagnetic Structures
Authors: Mirjanić D. Lj. , Bundalo Z. , Tošić B. S. , Šetrajčić J. P. 
Published: July 2007

AbstractThe spectrum of elementary excitations arising in processes of desintegration of magnon drops in one‐dimensional ferromagnetic structures is investigated. A new method of solving the gap equation is used. It is shown that those elementary excitations are gapless. This result is in accordance with Goldstone's theorem. It was also shown that these elementary excitations do not lead to the superfluidity effect.
Observation of FMR Surface Spin Wave Mode in Bulk Amorphous Ferromagnets
Authors: Frait Z. , Fraitová D. , Zárusová N. 
Published: July 2007

AbstractA secondary mode is observed (at RT) in the FMR spectra of the bulk amorphous alloy Fe40Ni40B20 subjected to an anneal at 250°C. This mode is interpreted as the surface spin wave mode because the observed magnetic resonance field dependences on the microwave frequency and on the direction of the external field towards the sample surface agree with the conclusions of the macroscopic FMR surface‐mode theory.
Symmetry Groups of Cyclic Systems in Crystals
Authors: Evarestov R. A. , Leko A. V. , Smirnov V. P. 
Published: July 2007

AbstractThe symmetry group of a cyclic system in a crystal is defined. Its relation to the space group of an infinite crystal is cleared up. It is shown that all the irreducible representations of the cyclic system symmetry group can be found from the definite representations of the space group. The connection between Herring's and reduction group methods developed in the space group representation theory and the large unit cell method is established. A simple and efficient method of the symmetry‐adapted atomic orbitals generation is proposed and illustrated by the examples for α‐quartz and β‐cristobalite crystals (space group D63 and O7h).
Thermodynamic Properties of Liquid Hydrogen Metal
Authors: Ebeling W. , Richert W. 
Published: July 2007

AbstractOn the basis of earlier found Padé‐approximations for the free energy and the chemical potential of a fully ionized hydrogen system the transition from the atomic to the metallic state is discussed. Partial ionisation is studied by using the mass action law. The second critical point for hydrogen is found to be Tc = 16500 K and Pc = 22.5 GPa. An updated phase diagram of the transition region is presented.
Critical Temperature of a Quasi‐One‐Dimensional Ising Model. The Bethe‐Peierls Approximation
Authors: Yurishchev M. A. 
Published: July 2007

AbstractThe critical temperature of a three‐dimensional spatially anisotropic Ising model is computed by the Bethe‐Peierls method applied to the five‐chain cluster. A comparison is made between the results obtained and calculations based on other approaches.
Far Infrared Absorption by Hot Holes in p‐Ge under E ⟂ B Fields
Authors: Pozhela Yu. K. , Starikov E. V. , Shiktorov P. N. 
Published: July 2007

AbstractA quantum mechanical approach and simulation of the hole energy distribution by Monte Carlo technique are used to calculate the field and wavelength dependences of the absorption crosssections of far infrared (λ = (40 to 500) μm) radiation by free holes interacting with phonons and impurity ions (σp) and due to the hole direct optical transitions between the light‐ and heavy‐hole subbands (σ12) for p‐type Ge in crossed electric and magnetic fields. The IR absorption by light‐and heavy‐holes emitting optical phonons is shown to increase sharply with E and dominate under strong heating. The absorption by holes interacting with impurity ions is shown to decrease significantly as the hole heating increases. This contribution can become negative. Under the population inversion of isomomentum states the amplification of the far IR radiation is shown possible only in the wavelength range λ = (40 to 200) μm. The necessary conditions are considered.
On the Theory of the Electron–Phonon Scattering Rate Including the Intra‐Collisional Field Effect
Authors: Ziep O. , Keiper R. 
Published: July 2007

AbstractA transport equation for ballistic charge carriers which contains the influence of strong and spatially inhomogeneous electric fields in the collision integral is derived by use of Airy functions. A simple analytical expression for the scattering rate due to electron–phonon interaction is obtained including the intra‐collisional field effect. Near the threshold energies for several electron–phonon interaction mechanisms strong modifications of the corresponding scattering rates are calculated whereas the field‐induced change of the scattering rate is negligible for high‐energetic carriers.
Temperature Dependence of the Liquid Tin Resistivity
Authors: Gasser J. G. , Bretonnet J. L. , Bruson A. 
Published: July 2007

AbstractThe temperature dependence law of the liquid metal resistivity is usually attributed to that of the atomic structure. In the framework of the Percus‐Yevick approximation applied to hard spheres, various laws of temperature dependence of their diameter are used. They are deduced from different physical or thermodynamical properties (self‐diffusion, structure, entropy, isothermal compressibility) or by minimizing the free energy. A comparison with experimental measurements on liquid tin up to 1300 °C leads to a fairly good agreement.
Transverse Phonon–Helicon Interactions in Semiconducting Plasmas
Authors: Ghosh S. , Pathak M. S. 
Published: July 2007

AbstractThe transverse phonon‐helicon interactions in semiconducting plasmas having piezoelectric or deformation potential coupling or both (viz., n‐InSb) are investigated when the waves propagating along z‐axis are subjected to a magnetostatic field B0 in z‐direction and the electrons are drifted with a velocity v0 also along the z‐axis. Using the hydrodynamic model of plasmas, the dispersion relation D(Ω, k) is derived. The conditions for excitation and the gain per radian of the acoustohelicon waves are studied in detail under slow wave approximation. The analysis takes into account hot carrier effects and the temperature dependence of the momentum collision frequency. The dependence of gain per radian on the system parameters is investigated. It is found that the heating of the carrier decreases the gain.
Phase Diagrams of Ferromagnets with Cubic Single‐Ion Anisotropy
Authors: Domański Z. , Sznajd J. 
Published: July 2007

AbstractThe phase diagrams of S = 2 and 5/2 ferromagnets described by an Hamiltonian with a cubic single‐ion anisotropy term are discussed. It is shown that in the case of S = 2 the sixth‐order terms in the LGW Hamiltonian do not change the qualitative picture of the phase diagram, recently presented, only shifting the tricritical points. On the basis of the RG results it is found that for S = 5/2 the phase transition to the state with magnetization along [111] direction ought to be continuous whereas that to the state [001] is a discontinuous one.
Soliton Excitations in Alternating Antiferromagnetic Linear Chains
Authors: Sy H. K. 
Published: July 2007

AbstractLinear chains of one half spins with anisotropic Heisenberg antiferromagnetic exchange are studied. Within the Hartree‐Fock approximation, such systems are shown to exhibit a spin‐Peierls transition. It is demonstrated here that the spin‐Peierls condensate also allows kink‐like soliton excitations, in analogy with the electron‐Peierls system. These spin‐solitons contribute to the magnetic susceptibility of the spin systems at low temperatures.
Magneto‐Reflectance of the B‐Exciton of CdS
Authors: Rosenzweig M. 
Published: July 2007

AbstractThe magneto‐reflectance of the B‐exciton of CdS is studied for fields up to 9.0 T. The spectra show a strong anisotropy of the Zeeman‐effect for H ⟂ c; the splitting is proportional to the sum of the g‐values of the valence and the conduction band for H parallel to the wave vector of incident light, but it is proportional to the difference of g‐values for H perpendicular to the wave vector. For the first time a change of the spectra with magnetic field inversion (pole‐changing effect) is observed; it appears for oblique incidence of light and results from the k‐linear term of the valence band. The spectra are discussed by lineshape analysis along the lines of excitonic polaritons. From the excellent agreement between experiments and calculations some new parameters of the B‐exciton can be determined: the g‐value of the B‐valence band g = 0.8 ± 0.1, the diamagnetic shift δdia = (2.0 ± 0.3) μe V/T2, and the different parts of the exchange interaction energy ΔLT = (1.4 ± 0.03) meV, Δ25 = (0.1 ± 0.05) meV and Δ21 = (0.15 ± 0.05) meV.
Excitons in Multi‐Layer Systems
Authors: Fomin V. M. , Pokatilov E. P. 
Published: July 2007

AbstractPotential theory Green functions for multi‐layer systems with anisotropic dielectric permeability are found. The effect of boundary conditions on the potential and exciton energy properties is studied. In three‐layer systems the decrease in thickness of dielectric layers with electrode‐covered outer surfaces results in the decrease of the absolute value of exciton ground state energy. In fivelayer systems the decrease in thickness of dielectric layers which are bounded by vacuum causes an increase of the absolute value of exciton ground state energy.
The Contribution of Davydov Solitons to the Value of the Kinetic Coefficient of Electron Transfer along a One‐Dimensional Molecular Chain
Authors: Ivić Z. , Satarić M. , Žakula R. 
Published: July 2007

AbstractAn expression is derived for the kinetic coefficient of the electron transfer from donor molecules (Dm) to acceptor molecules (Al) along a quasi‐one‐dimensional molecular chain, to which Dm and Al are statistically attached. Using the method of the non‐equilibrium statistical mechanics and coherent states representation, the influence is studied of the transfer mechanism of Davydov solitons on the value of the kinetic coefficient.
Radiative Decay from Free and Bound Excitons in GaSe
Authors: Capozzi V. , Caneppele S. , Montagna M. , Lévy F. 
Published: July 2007

AbstractSpontaneous excitonic luminescence in GaSe is investigated from 80 to 300 K and at weak laser excitation intensity. Radiative recombinations of direct and indirect free excitons are clearly observed. The analysis of the emission lines as a function of the temperature, of the excitation intensity, and of laser energy permits to attribute two lines of the intrinsic luminecsence to the recombination of direct and indirect excitons bound to defect centres localized in the energy gap. On the basis of recent theories on exciton‐impurity complexes, it is found that in the crystals the excitonic binding centres are deep neutral acceptors. From the dissociation energy of the bound excitons the ionization energy of the acceptor levels is estimated. Moreover, the measurements seem to indicate that thermal equilibrium between direct and indirect excitonic states is lacking below about 100 K.
Bound Exciton, Free‐To‐Bound and Electron‐Hole Plasma Luminescence in GaxIn1−xP (0.54 ≦ x ≦ 0.76)
Authors: Sotomayor‐Torres C. M. , Lumb M. D. , Walker G. 
Published: July 2007

AbstractThe luminescence of GaxIn1−xP (0.54 ≦ x ≦ 0.76) at 4.2 K is investigated. At high excitation intensities an electron‐hole plasma is observed in the sample with composition x = 0.54 and possibly in that with x = 0.74. No signs of an electron‐hole liquid are found in any of the samples studied. At low excitation intensities the luminescence spectrum is dominated by bound exciton transitions for samples with x = 0.76, 0.74, and 0.54 and by donor‐acceptor pair emission. For the sample with near crossover composition the spectrum is dominated by free‐to‐bound transitions. The results are discussed considering alloy disorder and are compared to those obtained in GaAs1−xPx and Ga1−xAlxAs under high excitation.