bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Concentration Fluctuation and Ordering Potential of LiPb in the Bhatia‐Young Approach
Authors: Bari A. , Joarder R. N. , Bhuiyan L. B. 
Published: July 2007

AbstractAn ordering potential out of the Thomas‐Fermi type interaction between dissimilar species based on the concept of charge transfer and hence concentration dependent, is constructed to study the thermodynamic properties of the LiPb alloy in the Bhatia‐Young formalism. It is seen to be fairly successful in predicting the experimental behaviour of concentration fluctuation and the excess stability in the system.
Presurface Exciton on the Media‐Parting Border
Authors: Paziuk V. V. , Tkach M. V. 
Published: July 2007

AbstractThe spectrum of the presurface exciton localized on the media‐parting border is found with the help of a self‐consistent method. The dependence of the spectrum on the effective mass component of the electron and hole correlation is obtained for arbitrary correlations between the permittivity values of the contacting crystals. The exciton spectrum can be described by three models depending on the static and dynamic characteristics of the contacting crystals: 1. the three‐dimensional exciton model, 2. the presurface exciton model, and 3. the model of electron and hole bound to their electrostatic images.
Dissociation of Electronic Excitations Localized near Vacancy Defects in KI Crystal
Authors: Vasilchenko E. , Sarmukiianov E. , Elango A. 
Published: July 2007

AbstractOn the example of a KI crystal it is shown that, together with the radiative decay of electronic excitaions localized near anion vacancies (cα) and vacancy quartets (cq), their nonradiative decay also occurs at 4.2 K. VK and F centers are created at eα decay and VK centers and electron vacancy complexes are created at cq decay. These defects arise as a result of eα and eq dissociation that occurs in the electric field of an anion vacancy or of a vacancy quartet. Some details of such a process are discussed.
Magnétorésistance de n‐CuInSe2 en régime métallique
Authors: Essaleh L. , Galibert J. , Wasim S. M. , Leotin J. 
Published: July 2007

AbstractUne étude du comportement électrique d'échantillons de n‐CuInSe2 de concentration électronique supéricure à la densité critique de Mott a été faite à bassc température et en champ magnétique jusqu'à 35 T. La variation de la magnétorésistance relative, à température fixée, en fonction du champ magnétique, dans la limite des champs faibles, est analysée dans le cadre des modéles tenant compte des effets d'interaction électron‐phonon et électron‐électron. L'étude de la conductivité totale, dans la limite des basses températures et des forts champs, montre que le terme de correction à la conductivité électrique, en régime métallique, est conforme au modéle de Kaveh et Mott.
Raman Scattering in nZnSIn2S3 Layered Compounds
Authors: Razzetti C. , Lottici P. P. , Bini S. , Curti M. 
Published: July 2007

AbstractPolarized Raman spectra obtained from carefully characterized single crystals of ZnIn2S4, Zn2In2S5, and Zn3In2S6 are reported. The low‐frequency Raman spectra clearly differentiate between the compounds, whereas at high frequencies the vibrational features are less sensitive to the actual crystal structure. The results are interpreted on the basis of a molecular‐like picture based on the intrinsic cationic disorder.
On a Generic Equation Modelling the Persistent Photoconductive Response of Semiconductor Devices
Authors: Anagnostakis E. A. 
Published: July 2007

AbstractA generic equation is proposed and discussed concerning the persistent photoconductive response of semiconductor devices, both of homostructure and heterostructure type, in terms of the sheet electron density evolution against the incoming cumulative photon dose. The equation models the persistent photoconductivity (PP) development up to saturation of the capacity of the fundamental conduction sub‐level accessible to the photoelectrons. The solution of the generic equation is effected through the respective Green's function, materialising the PP descriptor of the illuminated semiconductor structure, as the superposition of the eigenfunctions of the adjoint homogeneous Fredholm integral transformation.
Dynamical Theory of X‐Ray Diffraction by Elastically Bent Crystals with Microdefects I. Basic Equations
Authors: Kostyuk A. N. , Molodkin V. B. , Olikhovskii S. I. 
Published: July 2007

AbstractBasic equations of dynamical diffraction theory for elastically deformed single crystals with defects are obtained in the momentum space. The solutions for strong Bragg and diffuse waves are obtained and investigated in the two‐beam approximation. The corrections to Fourier components of the polarizability describing the influence of the diffuse and „quasi‐diffuse”︁ scattering on the attenuation of the amplitudes of strong Bragg waves are obtained in a general form.
A 35Cl NQR Study of [(CH3)2NH2]2SeCl6 Crystals
Authors: Horiuchi K. 
Published: July 2007

AbstractThe temperature dependence of the 35Cl NQR frequencies in [(CH3)2NH2]2SeCl6 is measured between 78 and 300 K. Two NQR lines with intensity ratio of 2:1 are observed at 196 K. The low‐frequency line fades out below about 80 K, while the other line is still clearly observed. This arises from a second‐order structural phase transition in which the librational modes of [SeCl6]2− anions become soft. Both lines fade out at higher temperature, however, the low‐frequency one at 26 K lower than the other one. This is explained by the C4 reorientional motions of the octahedral anions having a relative low activation energy of 18 kJ mol−1.
Effective Mass Theory for Abrupt Heterostructures
Authors: Brezini A. , Sebbani M. 
Published: July 2007

AbstractFor an abrupt heterojunction between two otherwise homogeneous semiconductors in one dimension the effective mass Hamiltonian

is studied with 2α + β = −1, where m(z) is the position‐dependent effective mass and Ec(z) the position‐dependent conduction band edge. Through exact model calculations on heterostructures, when the effective‐mass theory is valid the parameters α and β are found to be 0 and −1, respectively. This conclusion is obtained in the asymptotic limit of the energy near the band edge and holds for equal lattice parameters. Results are also compared to other theories.
Luminescence of KI: Pb Crystals
Authors: Nagirnyi V. , Nikl M. , Polak K. , Zazubovich S. , Jaanson N. 
Published: July 2007

AbstractSpectral, polarization, and kinetic characteristics of triplet luminescence of Pb2+vc− centres in KI:Pb are studied in the temperature range from 4.2 to 250 K. It is suggested that thermally stimulated T → X transitions as well as the transitions between T or X minima of various orientations can explain the temperature dependences of the intensities and the polarization degrees of luminescence (near 70, 30, and 130 K, respectively). It is concluded that in spite of a strong spin‐orbit coupling in the KI:Pb crystal, the Jahn‐Teller effect can be considered as the main interaction in the relaxed excited state (RES) of Pb2+vc− centres. A considerable influence of spin‐orbit interaction on the structure of RES was also detected.
Electronic and Electrochemical Properties of Nonstoichiometric Tungsten Diselenide
Authors: Molenda J. , Bąk T. 
Published: July 2007

AbstractResults of investigations on electronic (electrical conductivity and thermoelectric power) and electrochemical properties of non‐stoichiometric tungsten diselenide are presented in the paper. It is proved that holes connected with non‐stoichiometry (W1−xSe2) are the dominating current carries within the temperature range 77 to 300 K. A qualitative scheme of the electronic structure of W1−x‐Se2 is proposed. A strict correlation between the electronic and electrochemical properties of tungsten diselenide is proved for the cell of Li/Li+/Liy W1−xSe2 type.
Long‐Wavelength Absorption in Small Metallic Spheres
Authors: Olszewski S. 
Published: July 2007

AbstractThe absorption of electromagnetic waves by the free‐electron gas in a metal can be calculated if the standing‐wave‐like character of the electron wave functions is taken into account. This approach differs from the zero light absorption obtained from the electron wave functions having the cyclic boundary conditions given by Bloch. For long wavelengths the theory is applied to the case of small metallic spheres. For sludges of copper and lead the calculated absorption coefficient at frequencies above 1012 Hz is found to be quite close to the observed data.
Dielectric Screening and Phonon Dispersion in Metallic Glasses
Authors: Agarwal P. C. , Azez K. A. , Kachhava C. M. 
Published: July 2007

AbstractExpressions for the phonon frequencies of the binary and ternary metallic glasses are derived on the basis of various dielectric screenings. A model which assumes a central force, effective between nearest neighbours, and a volume dependent force is adopted. The phonon frequencies of longitudinal and transverse phonons for the binary metallic glasses Ca70Mg30, Mg70Zn30, and Cu57Zr43 and for the ternary metallic glass Pd77.5 Si16.5Cu6 are computed. The theoretical results compared with experimental data underline the importance of dielectric screening by conduction electrons.
Description of the Mechanical Properties of Viscoelastic Materials Using a Modified Anelastic Element
Authors: Hermida Élida B. 
Published: July 2007

AbstractQuasi‐static and dynamical tests are employed to measure the modulus or the compliance of a material as a function of time or frequency, and to determine the respective distribution function in the case of a linear viscoelastic medium. The evolution of the mechanical properties, and consequently the distribution functions, are usually described by empirical expressions which cannot always be interpreted according to a physical model. Furthermore, as a rule these empirical distributions do not lead to closed expressions for all the viscoelastic functions. The mechanical properties of viscoelastic materials (amorphous polymers, metallic glasses, etc.) are described using a modified anelastic element (MAE). This modified element is analogous to the standard anelastic element, having a single characteristic time, τ, that is not a constant but a function of time or frequency. On considering a particular functional dependence of τ, it is demonstrated how several empirical viscoelastic functions are approximations of the mechanical properties of the MAE. Moreover, this functional dependence is related to the log‐normal distribution the statistical and physical meanings of which are discussed in detail.
Effects of Electron(Hole)–SO‐Phonon Coupling on the Ground Exciton State in Quantum Wires
Authors: Sheng Wei‐Dong , Gu Shi‐Wei 
Published: July 2007

AbstractTaking account of electron(hole)–SO‐phonon coupling, the ground exciton state in free‐standing quantum‐well wires with circular cross‐section is studied in detail. Two unitary transformations are carried out, the SO‐phonon‐induced potential in ϱ‐direction and the SO‐phonon‐induced interaction between an electron and a hole in z‐direction as well as the effective Hamiltonian of the exciton–SO‐phonon systems are obtained. The ground exciton state binding energy is calculated from a trial wave function separable in spatial coordinates. An unexpected result is obtained: although the electron (hole)–SO‐phonon coupling is very strong in quantum wires, its influence on the exciton binding energy is not so notable as that in 3D or 2D exciton‐phonon systems.
Quadratic Crystal‐Field Effects on the J = 15/2 Manifold in Cubic Symmetry
Authors: Kornienko A. A. , Kaminskii A. A. , Dunina E. B. 
Published: July 2007

AbstractThe effects of electron correlation resulting from one‐particle operators in third order are investigated. These effects are presented by an effective Hamiltonian having the form of a “quadratic crystal‐field”. The fitting to the Stark structure of the J = 15/2 manifold by the “quadratic crystal‐field” Hamiltonian gives good agreement with experimental data. The “quadratic crystal‐field” Hamiltonian may be useful for the analysis of the energy‐level scheme of Pr3+ ions in LiYF4 crystal, where there are problems in describing the higher manifolds by an effective one‐electron Hamiltonian.
Practicable Method for Estimating Thermal Depths from Phonon‐Broadened Photoexcitation Cross‐Section Bands. III. Generalization for Charged Centres
Authors: Pässler R. 
Published: July 2007

AbstractThe zero‐phonon threshold behaviour of thermally broadened absorption cross‐sections σ(hv, T) is examined for deep traps retaining a non‐zero net charge after the carrier excitation processes in consideration. The influence of a corresponding attractive or repulsive Coulomb potential on threshold properties of these absorption cross‐sections is described within the framework of conventional Sommerfeld factors. Concerning the characteristic vertex positions of transformed excitation curves ϱ(hν, T) ≡ exp (‐ hν/2kT) σ(hν, T), we attain in simple ways to analytical expressions for upper and lower bounds representing the limiting regimes of extremely strong and vanishing electron‐phonon coupling. Specializations for alternative charge‐state regimes give average vertex‐position versus thermal‐depth shifts of (½ + f) 2kT for attraction and \documentclass{article}\pagestyle{empty}\begin{document}$\(\sqrt[3]{{\pi ^2 R/2kT}} + \frac{5}{{12}} + \frac{2}{3}f) $\end{document} 2kT for repulsion (where f = 0 or 1 in cases of allowed or forbidden transition and R is the relevant Coulomb‐barrier Rydberg energy). The absorption threshold behaviours of hole excitation curves due to a series of second donor levels in silicon can be well understood under the assumption of allowed transitions affected by a repulsiue barrier whose actual strength is determined just by the light hole band (R → 15 meV). From experimental σp(hν, T) curves given by Grimmeiss and Skarstam we detect hole ionization energies Jp(T → 0) of about 553 meV for Si : S and 572 meV for Si : Se. Assessing the experimental σp(hν, 77 K) curves given by Tilly et al. we come to hole ionization energies Jp (77 K) of about 251 meV in case of Si: Ti and 356 meV in case of Si: V. All these semiempirical Jp values are found to be in reasonable agreement with other available data.
Electric Field Gradient Calculations in Hexagonal Tungsten Bronze Type Fe3+ Fluorides: (H2O)0.33FeF3 and Anhydrous FeF3
Authors: Leduje D. , Teillet J. 
Published: July 2007

AbstractThe polarisahle point‐charge model is used to calculate the electric field gradient (EFG) tensor at the Fe site in the two compounds (H2O)0.33FeF3 and anhydrous FeF3. The results are consistent with experimental Mösshauer data for a fluorine polarizability of 8 × 10−4nm3. Calculations on (H2O)0.33 FeF3 provide two very close quadrupole splittings (ΔEQ = 0.62 and 0.65 mm s−1) whereas calculations on anhydrous FeF3 provide only one quadrupole splitting (ΔEQ = −0.38 mm s −1).
A Novel Mechanism for the Kossel Effect Due to Coherent X‐Ray Scattering in Periodic Amorphous Multilayers
Authors: Jianc Xiaoming , Metzger T. H. , Peisl J. 
Published: July 2007

AbstractA new mechanism for the the excitation of the Kossel effect is observed in periodic amorphous multilayers, where the X‐rays, scattered coherntly from atoms in the amorphous state, act as the sources within the one‐dimensional periodic multilayer. The Kossel effect, which is well described by the distorted‐wave Born approximation, is manifested as intensity modulations whenever the exit angle of the scattered beam equals any Bragg angle of the multilayer diffraction. While it is initially surprising for an amorphous sample, this Kossel effect must be treated by dynamical theory and will only occur for sharp interfaces between W and C sublayers.
Velocity of Sound and Resistivity Measurements on Amorphous FeCrB, FeMnB, and FeNiB during Structural Relaxation
Authors: Riontino G. , Koebrugge G. W. , Baricco M. , Sietsma J. 
Published: July 2007

AbstractThe velocity of sound and the electrical resistivity of amorphous Fe75Cr5B20, Fe75Mn5B20, and Fe75Ni5B20, are measured during isothermal heat treatments. It is shown that different types of measurements are indeed necessary in order to reach sensible conclusions on relaxation mechanisms, since one measurement only is prone to multiple interpretation. Without reference to any specific model, the present study sheds some light on the nature of the atomic rearrangements involved in the structural relaxation processes, combining the results of two experimental techniques and three related compositions.
Computer Simulation of the 36.87° [001] {310} Symmetrical Tilt Grain Boundary Structure in B.C.C. Metals
Authors: Erhart J. , Trubelík I. 
Published: July 2007

AbstractThe stable atomic arrangements of the 36.87° [001] {310} symmetrical tilt grain boundary structure in b.c.c. metals are calculated using the method of molecular statics. Four different atomic structures, which differ in the energy, rigid body displacement of the grains, and the shift of the boundary plane, are found.
Vibrational Properties of Pd1−c Fec Disordered Binary Alloys
Authors: Upadhyaya S. C. , Prakash D. , Sharma D. K. , Shyam R. , Upadhyaya J. C. 
Published: July 2007

AbstractThe transition metal model potential of Animalu is applied to study the lattice dynamics of two f.c.c disordered alloys of Pd and Fe, namely Pd0.96Fe0.04 and Pd0.90Fe0.10 First the model potential is uscd to compute the radial and tangential force constants of Pd and Fe for the two alloys and also those of pure Pd up to ten sets of nearest neighbours. The concentration average of these force constants is used to determine the force constants of the two disordered alloys. Next, the dynamical matrix is constructed and the secular equation is solved to calculate the phonon dispersion curves and elastic constants of pure Pd and Pd0.96Fe0.04 and Pd0.90Fe0.10 alloys. In all the cases a reasonably good agreement is found between the computed and experimental results, when three‐body forces are incorporated in the interaction system. Phonon density of states and the temperature dependence of specific heat and Debye temperature of the two alloy systems are also computed and presented.
Electronic Structure of Aluminum Surfaces. Results from Empirical Tight‐Binding Scattering Theory
Authors: Würde K. , Mazur A. , Pollmann J. 
Published: July 2007

AbstractThe results of an empirical tight‐binding study of the electronic properties of Al surfaces are reported. The underlying bulk crystal is described by a realistic first‐nearest‐neighbour empirical tight‐binding Hamiltonian which includes s‐, p‐, and d‐orbitals. The electronic structure of the (OO1), (110), and (111) surfaces is calculated for semi‐infinite systems employing the scattering theoretical method. Our results are compared with the results of other calculations and with experimental data. For a few representative cases we analyse the origin and nature as well as the spatial localization of the surface states.
Core Hole Effect on the XAS Si K Edge Shape in α‐Quartz
Authors: Jollet F. , Noguera C. 
Published: July 2007

AbstractThe role of the core hole effect on the Si K X‐ray absorption spectrum of α‐quartz is established thanks to two electronic structure calculations: 1. a self‐consistent band structure approach at ambient pressure and under hydrostatic pressure, that accounts for the gap and the valence band shape, and that provides the empty density of states of α‐quartz, is shown to be unable to reproduce the experimental Si K edge shape; 2. on the opposite, a self‐consistent embedded cluster calculation, which allows to include the effect of thc core hole yields a local p density of states on an excited silicon atom which compares satisfactorily with the experimental spectrum.
Magnetic Susceptibility of Copper Oxide Based Antiferrornagnets in an Anisotropic Heisenberg Model
Authors: Singh R. P. , Tao Z. C. , Singh M. 
Published: July 2007

AbstractThe RPA Green's function theory is extended to study the magnetic properties of copper oxide based antiferromagnets in an anisotropic Heisenberg model. It is shown rather generally by the use of spectral representation that the magnetic properties of copper oxide based antiferromagnets have a crossover from 3D to quasi‐2D behavior near the temperature (≈ 2J∥ √2r/kB). Here J∥ is the intraplanar exchange coupling strength and r the ratio of interplanar to intraplanar coupling strengths. The magnetic susceptibility as a function of temperature is calculated numerically. Our numerical results are compared with experimental measurements of the magnetic susceptibility on La2CuO4_y compounds. It is found that the RPA magnetic susceptibility agrees reasonably well with experiments at high temperatures, but misses totally the peak near the temperature (≈2J∥/kB).
A Contribution to the Mean‐Field Analysis of Amorphous Magnets
Authors: Millev Y. , Fähnle M. 
Published: July 2007

AbstractA method is outlined to obtain explicit analytical solutions for Handrich's mean‐field model of amorphous ferromagnets for the general spin quantum number S and the structural disorder parameter δ. The explicit solutions are given for S = 1/2 and δ = 1/3 and 1/2.
The Magneto‐Optical Kerr Effect in Co‐Based Multilayered Structures
Authors: Zhou Shi‐Ming , Chen Liang‐Yao , Su Yi , Qian You‐Hua 
Published: July 2007

AbstractIn this paper calculated magneto‐optical Kerr rotation spectra of Co/Pd, Co/Pt, and Co/Cu multilayers are presented. For Co/Pd and Co/Pt multilayers with a top Co layer the size of Kerr rotation |θ|k increases with increasing modulation wavelength. For Co/Cu multilayers with a top Co layer |θ|k increases with modulation wavelength increasing to 40 nm and then decreases with the modulation wavelength further increasing to 60 nm. For all these multilayers with a top non‐magnetic layer |θ|k decreases with increasing modulation wavelength. The optical constant effect of the non‐magnetic sublayer is discussed.
A Spatial Characteristic Scheme for Multigroup Discrete Ordinates Electron Energy Deposition in Two Dimensions
Authors: Datta R. P. , Ray A. K. 
Published: July 2007

AbstractEnergy deposition calculations are performed due to an incident source of electrons in rectangular slab geometry using the method of discrete ordinates for directions and the multigroup treatment in energy. Using the restricted stopping power formalism to distinguish between large energy loss collisions (catastrophic) and small energy loss collisions (continuous), coupled with a second‐order differencing scheme in energy, an improved model of electron energy loss is incorporated in our computational model. Results are presented for isotropic and normal incident sources and compared with available results.
Reversibility of a Phase Transition in KDP under Uniaxial Stress
Authors: Melo F. E. A. , Moreira S. G. C. , Filho J. Mendes , Moreira J. E. 
Published: July 2007

AbstractRaman spectra of KDP, taken at a temperature near the paraelectric‐ferroelectric transition and submitted to a uniaxial stress show two new phase transitions. The change of symmetry of the ion units due to these transitions is related to the spectroscopic results. The reversibility of the transitions when temperature and pressure are cycled around the transition lines is discussed.
Magnetic Properties of a Transverse Spin‐1 Ising Model with Longitudinal Crystal Field Interactions
Authors: Benyoussef A. , Ez‐Zahraouy H. 
Published: July 2007

AbstractThe three‐dimensional spin‐1 Ising model with crystal field interactions exhibits tricritical behaviour. Using an expansion technique for cluster identities of spin‐1 localized spin systems, the influence of transverse magnetic field on this behaviour is studied. Temperature‐crystal field phase diagrams are investigated for different values of transverse field. The longitudinal and transverse magnetizations, as well as the quadrupolar moments are calculated. General formulas applicable to structures with arbitrary coordination number N, are given.