bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Study of the Gradual Chemical Transition at the SiSiO2 Interface. II. Electronic Density of States Calculations
Authors: Hübneb K. , Stern A. , Klinkenberg E.‐D. 
Published: July 2007

AbstractCalculations of the electronic density of states at the Si‐SiO2 interface performed with the help of the cluster‐Bethe‐lattice method are presented. A cluster is constructed, which realizes the semiconductor‐insulator transition between a Bethe lattice of Si atoms and an SiO2 Bethe lattice within three atomic SiOx layers with average x values of 0.33, 1.17, and 1.67. The resulting densities of states are compared with corresponding results for bulk SiOx and the static effective charges of all the cluster atoms are calculated. It is shown that an intermediate‐range order (Si‐Si chains and rings) strongly influences the position of the valence‐band edge and, therefore, the variation of the width of the gap in dependence on the chemical composition x across the Si‐SiO2 inter‐region. The defect levels resulting from dangling bonds of Si atoms with different backbond configurations and from a peroxy bridge and a peroxy radical are investigated. An influence of structural percolation effects on the dangling‐bond levels is shown. Further microscopic origins of interface states are discussed.
The Gryromagnetic Factor of Conduction Electrons in Silver, Gold, Palladium, and Platinum
Authors: Schober C. , Kurz G. , Wonn H. , Nemoshkalenko V. V. , Antonov V. N. 
Published: July 2007

AbstractFor the gyromagnetic factor of the conduction electrons in metals a rigorous relativistic theory is developed generalizing Roth's theory, within which the Pauli formalism is used. In a first test calculation the g‐shift is calculated for Ag, Au, Pd, and Pt in spherical approximation. The calculations yield a negative g‐shift for Ag and a positive g‐shift for Au, Pd, and Pt in agreement with the experimental results.
On the Concept of Intermediate One‐Particle States in Finite Chains. A Self‐Consistent Field Study
Authors: Liegener C.‐M. , Biczó G. , Godzik A. 
Published: July 2007

AbstractAb initio self‐consistent field calculations are performed on finite chains of hydrogen atoms and other model systems to test the prediction of a quantum‐size effect, namely the arising of intermediate one‐particle states. The calculations confirm earlier conjectures concerning the appearance of intermediate states, not only at the simple Hückel, but also at the self‐consistent field level of approximation. Furthermore, the stability of intermediate states with respect to perturbations is studied.
Surface Excitations on Small Metal Particles by Fast Electrons
Authors: Bao Tran Thoai Duy 
Published: July 2007

AbstractInelastic scattering of fast electrons by isolated small metal particles is studied within the hydro‐dynamic model. The energy loss probability for multipole surface modes is calculated. Numerical calculations for rs = 2 jellium are carried out for different parameters: fast electron energy, electron impact parameter, radius of the partide, and energy loss.
Dielectric Dispersion in Tris‐Sarcosine Calcium Chloride (TSCC)
Authors: Pawlaczyk Cz. , Unruh H.‐G. , Petzelt J. 
Published: July 2007

AbstractDielectric dispersion of TSCC single crystals of three different qualities is investigated in the frequency range 102 to 6 × 109 Hz in the close vicinity of Tc. Up to three dispersion regions are found where only in the highest frequency one the results are nearly sample independent. They can be roughly fitted to a Debye law where the relaxation frequency obeys the classical critical slowing‐down law fε = A(T  Tc) with A = 0.23 cm−1 K−1 and Tc = 130.5 K for 130.7 K < < T < 131.4 K. The results are connected to the far infrared soft‐mode dispersion observed by Kozlov et al. and analyzed using the two‐coupled‐mode model. Although the phase transition is driven by the displacive soft‐mode coordinate, close to Tc a strong mixing with a pseudospin relaxing coordinate takes place. The discussion concerning the character of the phase transition in TSCC can be concluded stating that the dynamical origin of the instability leading to the phase transition is overwhelmingly of the displacive type. However, due to the disorder present in the paraelectric structure, the soft‐mode eigenvector becomes temperature dependent near Tc and at Tc it consists of an equal mixture of both the mode coordinates.
Infrared Lattice Vibration, Dielectric Dispersion, and Lattice Dynamics of BaFCl
Authors: Sieskind M. , Ayadi M. , Zachmann G. 
Published: July 2007

AbstractThe reflectivity of single crystals of BaFCl is measured in the wave number range from 30 to 5000 cm−1 at room temperature using a Fourier transform infrared spectrometer. The recorded reflection spectra are evaluated by means of the classical oscillator model and the Kramers Kronig analysis in order to get the TO and LO frequencies and the optical constants. The calculated effective dynamical charges of the involved ions are found to be in good agreement with the results obtained using a shell model.
Precise Measurement of the Free Electron g‐Factor in InSb
Authors: Vdovin A. V. , Skok E. M. 
Published: July 2007

AbstractThe dependence of g‐factor of free electrons in n‐InSb on magnetic field and concentration is investigated by the spin‐flip Raman scattering gain method (SFRS method). The correct values of g‐factor at the conduction band edge g0 = −51.55 ± 0.02 and dg/dH (H ∥︁ [100]) = (2.06 ± ± 0.02) (I/T) are obtained by extrapolation of these values to zero field and concentration. The value of g0 agrees well with the data obtained by electron spin resonance (ESR) method (g0 = = −51.53). The g‐factor anisotropy coefficient γ = (0.095 ± 0.004) (1/T) is measured at H = = 0.9434 T. The values m*/m0 = 0.0135 ± 0.0001, EP = (24.55 ± 0.2) eV, EQ = (17.8 ± 1) eV, E'P = (6.0 ± 3.8) eV, F = −2.0 ± 0.4 and N1 = −0.04 ± 0.03 are obtained by using the parameters: Δ = (0.803 ± 0.005) eV and Eg = (0.2368 ± 0.0002) eV.
Bisolitons in a Molecular Polymer Chain
Authors: Ristovski Lj. , Davidović‐Ristovski G. S. , Ristić V. 
Published: July 2007

AbstractA molecular chain in which two types of tight‐bound excitons are excited, is considered in the continuum approximation. The exciton‐exciton and exciton‐lattice interactions are taken into account. The strong exciton‐lattice coupling causes the appearance of autolocalized excitons, viz. solitons. In the case considered two types of interacting solitons can appear. The soliton‐soliton interaction causes the creation of a bound state, the bisoliton, which propagates along the chain, as a free particle‐like autolocalized excitation with an interior degree of motion. The bisoliton effective mass and energy are determined and analysed.
Dynamical Model for the Lattice Frequencies and Crystal Field Splittings of Carbon Disulphide
Authors: Higgs J. F. , Anderson A. 
Published: July 2007

AbstractA simple force constant model is used to calculate the normal mode frequencies and eigenvectors of the carbon disulphide crystal. By adjustment of three intramolecular and four intermolecular parameters, good agreement with spectroscopic data is obtained for the lattice mode frequencies and for the crystal field splittings of the molecular modes.
Temperature Dependence of Resonance Splittings in Molecular Pairs. Comparison of Optical Experiments and Theoretical Results for the Phenazine Triplet State
Authors: Reineker P. , Winkler R. G. , Port H. 
Published: July 2007

AbstractThe temperature dependence of the resonance splitting is calculated for pairs of translationally equivalent and inequivalent molecules in a molecular crystal using a canonical transformation method. The model Hamiltonian takes into account the excitonic transfer matrix element and linear local coupling between excitons and both acoustic and optical phonons. The calculations are successfully applied to optical data obtained for triplet excitons in phenazine.
The F+‐Centre in Alkali Oxides of Antifluorite Structure. a Model Potential Numerical Calculation
Authors: Kassim H. A. 
Published: July 2007

AbstractAbsorption energies of the F+‐centre in Li2O and other alkali‐oxides of antifluorite structure are calculated numerically using the point ion and model potentials incorporating core repulsion based on the modified Bartram, Stoneham and Gash pseudopotential as proposed by Matthew and Green. Other effects such as electronic polarization and ionic distortion are also considered. The results obtained are in good agreement with the experimentally assigned value for the band peak position and with the recent variational calculations by Ong on the same systems.
Negative Momentum Relaxation Rate and Transport in Polar Semiconductors
Authors: Dimoulas A. 
Published: July 2007

AbstractThe possibility of a negative momentum relaxation rate by absorption of polar optical phonons in a non‐degenerate semiconductor is examined. Charge density wave propagation is predicted as a result of this. The wave sets up an average dc field in which the electrons respond in such a way that a dc current independent of the external field flows. This implies that a persistent current could flow in the solid.
Momentum‐Dependent Dielectric Response of Strongly Heterogeneous Materials with Anisotropic Components
Authors: Drechsler S. L. , Bobeth M. 
Published: July 2007

AbstractAn effective medium approach (CPA) for calculating the static wave‐number‐dependent effective dielectric function of strongly heterogeneous composites with randomly oriented anisotropic components is presented, where the composite is supposed to consist of a random arrangement of homogeneous regions (grains) with known material properties. Final formulae governing the effective dielectric function at arbitrary wave numbers are given for spherical and cylindrical grain shapes. In the long‐wavelength limit the general case of ellipsoidal shape is considered and a marked dependence of the effective permittivity on the eccentricity is obtained for moderate and large anisotropy.
Calculation of Compton Profiles of Tantalum and Tungsten
Authors: Papanicolaou N. I. , Bacalis N. C. , Papaconstantopoulos D. A. 
Published: July 2007

AbstractCalculations of the Compton profiles for the transition metals Ta and W are performed, using electron wave functions obtained from self‐consistent augmented plane wave (APW) band structure calculations within the local density formalism of Hedin‐Lundqvist. Relativistic effects are included except for the spin‐orbit interaction. The observed structures of the Compton profiles in these metals are understood in terms of the topology of their Fermi surfaces.
Dependence of the Low Temperature EPR Spectrum of Cu2+ Ion on the Microwave Field Frequency and Temperature
Authors: Vasyukov V. N. 
Published: July 2007

AbstractThe EPR spectrum of the Cu2+ ion in octahedral environment is calculated with the account of the Jahn‐Teller effect within the cluster model. The study of the frequency dependence of the EPR spectrum is used as a basis for the estimation of parameters of the Hamiltonian describing the behaviour of the system. The appearance of an additional isotropic line and drop of intensities of the resonance lines of the low temperature spectrum with the temperature increase are explained on the basis of the population of a great number of excited states and their properties.
Thermoluminescence Study of CaF2:Nd Single Crystals from LNT to 400 °C
Authors: Subramanian Uma , Mukherjee M. L. 
Published: July 2007

AbstractThermoluminescence and X‐Ray fluorescence of single crystal of CaF2:Nd are studied earlier. Since the major emission is in the infrared, attention is denoted to this region only. Although, there are reports that strong emission in the visible is also observed, detailed results are not available in the literature. In this paper, thermoluminescence (TL) emissions in the UV and visible region are studied in the temperature range between liquid nitrogen temperature and 400 °C. Several parameters associated with the TL emission are also calculated. A tentative mechanism for concentration dependence of the 315 °C TL peak is suggested.
Thermopower in Quasi‐Two‐Dimensional Semiconductor Quantum Well Structures
Authors: Kubakaddi S. S. , Mulimani B. G. , Jali V. M. 
Published: July 2007

AbstractExpressions for the thermopower in quasi‐two‐dimensional semiconductor quantum well structures are obtained in the extreme quantum limit when electrons are scattered by acoustic phonons via deformation potential coupling, polar optical phonons, and ionized impurities. Numerical results are given for the size dependence of thermopower. It is found to be enhanced over its bulk value for lower values of well thickness. The contributions from individual scattering mechanisms are found to increase with the increase of temperature.
X‐Ray Electron Density Distribution of GaAs
Authors: Pietsch U. , Tsirelson V. G. , Ozerov R. P. 
Published: July 2007

AbstractUsing ten X‐ray structure amplitudes of strong reflections and nine weak reflections both, the valence electron and the difference electron density distribution of GaAs, are calculated. The experimental data are corrected for anomalous dispersion using a bond charge model. The calculated plots are compared with up to now published band structure‐based and semiempirically calculated density plots. Taking into account the experimental data of germanium, measured on the same absolute scale, the difference density between GaAs and Ge is calculated. This exhibits the charge transfer between both the f.c.c.‐sublattices as well as both, the shift and the decrease of the bond charge, quite closely connected to the theoretical results published by Baur et al.
Electron Paramagnetic Resonance Analysis of Strain‐Induced Defects in Semi‐Insulating GaAs
Authors: Benakki S. , Goltzene A. , Schwab C. , Guangyu Wang , Yuanxi Zou 
Published: July 2007

AbstractA series of plastically deformed GaAs samples is investigated by EPR at 9 GHz. The spectra show that the expected As quadruplet is correlated with a new spectrum over the whole strain range. These results are discussed within a model justifying the predominant role of different anionic antisite linked complexes according to the experimental generation conditions.
A New Correlation Energy Interpolation Functional for Many‐Electron Systems in the Homogeneous Electron Gas Model. The Ratio of Paramagnetic and Ferromagnetic State Energies versus Gas Density
Authors: Gritsenko O. V. , Zhidomirov G. M. 
Published: July 2007

AbstractAn interpolation method is suggested to calculated the correlation energies ϵ{ϱ} and ϵ{ϱ} of para‐ and ferromagnetic states of an homogeneous electron gas of any density ϱ. The functions ϵ{ϱ} and ϵ{ϱ} plotted in this method reproduce an exact dependence of correlation energy on gas, ϱ, in the limits within ϱ → infin; and ϱ → 0, as well as the empiric correlation energies of atoms. With the obtained functions, ϵ and ϵ, the possibility of appearance and suppression of ferromagnetism when varying the density of electron gas is investigated. Paramagnetic susceptibility of gas as a function of ϱ is calculated, and the results obtained are compared with the experimental data for Na and K.
Collective Magnetic Order and Intermediate Valence in the Anderson Model
Authors: Reddy G. Gangadhar , Ramakanth A. 
Published: July 2007

AbstractThe question of the coexistence of long range magnetic order and intermediate valence is investigated using the periodic Anderson model. The average occupation nf of the relatively well localized 4f level and the corresponding magnetization mf are selfconsistently calculated keeping the total number of electrons N per lattice site fixed. The Curie temperature TC is determined following the temperature variation of mf. The behaviour of TC as a function of the position of the localized 4f level Ef for a constant Bloch band width W and as a function of W for a constant Ef are studied for different values of N. The results are interpreted in terms of the interplay between the relative occupation of the f‐level and the conduction band and the fluctuations caused by the hybridization. Similarities with experimental results are pointed out. A phase diagram is constructed which indicates the constellations of model parameters which permit long range magnetic order.
The Application of the Differential Operator Method to the Calculation of Magnetization in Thin Ferromagnetic Films
Authors: Wiatrowski G. , Balcerzak T. , Wojtczak L. , Mielnicki J. 
Published: July 2007

AbstractOn the basis of differential operator method the critical temperature and magnetization vs. film thickness are calculated in the frame of the Ising model. The magnetization changes across the film, and the corresponding magnetization profiles for several values of reduced temperature are presented. All the results obtained are calculated for the particular case of S = ½ and for a film with s.c. lattice, although another crystallographic lattices may be considered as well.
Increasing Absorption Bistability of CdS at Room Temperature
Authors: Haddad I. , Kretzschmar M. , Rossmann H. , Henneberger F. 
Published: July 2007

AbstractVisible‐wavelength increasing absorption bistability at room temperature is shown due to lattice heating of CdS in a fully cw‐regime. Cross talk of two beams and the switching behaviour of the bistable system are investigated. For the first time critical slowing down is demonstrated for this type of optical bistability. Quantitative theoretical investigations based on the heat flow equations yield an excellent agreement with the experimental data.
Correlations between Electron Paramagnetic Resonance and Bonding Parameters. Evidence of a Lattice Relaxation
Authors: Souiri M. , Goltzene A. , Schwab C. 
Published: July 2007

AbstractThe study of the correlations between bonding parameters (ionicity, bond length) of a crystal and some spin‐Hamiltonian parameters of a magnetic probe allows to demonstrate the occurrence of a lattice relaxation induced by the condition of a constant bond length between an identical pair of bonded ions, independently of the host matrix under consideration.
A Silicon–Gold Pair in Silicon Investigated by EPR
Authors: Höhne M. 
Published: July 2007

AbstractA new gold‐related defect in silicon is observed after IR irradiation. Though a thermal treatment including additional doping with lithium is necessary for the production of this centre, the lithium obviously does not participate in the paramagnetic state. The paramagnetic state is mainly localized at a silicon atom and a gold atom, both forming a trigonal pair. The interaction with six groups of three equivalent silicon ligands is partly resolved. The g‐values are compared with those of other gold‐related defects in silicon. Models are discussed.
Lattice Dynamics of Transition Metals
Authors: Thakur V. K. , Singh T. N. 
Published: July 2007

AbstractA phenomenological model for the lattice dynamics of face centred cubic transition metals is developed. The potential energy of the crystal lattice is considered as due to (i) ion–ion and (ii) ion–electron interactions. The force‐field involving ion–ion interaction is essentially a three body force model employing valence force field approximations. The contribution to the potential energy from ion–electron interaction is considered by a screened Coulomb potential. Phonon dispersion curves, specific heat, and Debye characteristic temperature of nickel, palladium, and thorium are computed on the basis of the model developed. Computed results are compared with the experimental ones.
The Electrostatic Lattice Energy
Authors: Olives J. 
Published: July 2007

AbstractThe limit volumic electrostatic energy of a crystal lattice of point charges is compared to the Born‐Landé expression and to the Ewald energy. Conditions are given about the existence of these energies, and the results are expressed in an integral form; a second integral form is obtained by application of Plancherel's theorem. The volumic electrostatic energy depends on the surface of the crystal (owing to the long‐range I/r dependence of the electrostatic energy). Information about the atomic configuration of the surface of the crystal, is obtained by minimization of the volumic energy (the minimum being the Ewald energy).
Lattice Vibrations in BiLiF4 and YLiF4
Authors: Schultheiss E. , Scharmann A. , Schwabe D. 
Published: July 2007

AbstractResults of Raman studies of BiLiF4 and YLiF4 single crystals at 300, 77, and 4.2 K and powder pellets of these materials at 300 K are reported. The observed vibrations are assigned to the irreducible representations of the space group of the crystals.
Spin‐Wave Spectrum in Uniaxial Ferromagnetic Thin Films with Nearest‐Neighbour and Next‐Nearest‐Neighbour Exchange Couplings
Authors: Duda A. 
Published: July 2007

AbstractThe standing spin‐wave spectrum is analysed for the uniaxial ferromagnetic thin film with nearest‐neighbour and next‐nearest‐neighbour exchange interactions. The boundary conditions are described in terms of the uniaxial surface anisotropy. It is found that the nnn exchange interactions give rise to new types of bulk and surface spin‐wave modes. The properties of the new modes are discussed in their dependence on both, nnn coupling and surface anisotropy parameters.
Calculations on Relaxations Due to a Vacancy, Binding Energy of a Vacancy—Vacancy Pair, and Formation Energy of a Vacancy in Thorium
Authors: Ghorai A. , Sen S. K. 
Published: July 2007

AbstractThe lattice statics method is used to calculate the relaxations due to a vacancy created in a lattice. The measured phonon dispersion relations and the elastic constants are used as constraints to calculate the dynamical matrix considering interactions up to eighth neighbour. The calculation shows that the first three shells of atoms relax towards the vacancy. The divacancy binding energy is found to be 0.477 eV which agrees well with simpler model calculation. Considering the uncertainty in the experimental value the agreement between the calculated and experimental value of the monovacancy formation energy is fairly good.
Electron Momentum Density Distributions in Rhodium
Authors: Bonde H. P. , Shrivastava S. B. 
Published: July 2007

AbstractCalculations of two photon momentum density distributions (TPMD) and the electron momentum density distributions (EMD) are made in the 4d metal rhodium. Results are presented and discussed in terms of band by band contributions, along important symmetry directions. A comparison of TPMD results is made in the metals Rh, Pd, and Ag.
The Long‐Wavelength Magnon Relaxation in Ferromagnetic Metals at T ⪅ Tc
Authors: Lutovinov V. S. 
Published: July 2007

AbstractThe spin wave (SW) relaxation processes in ferromagnetic metals are considered in the framework of the spin operator diagram technique in a wide range of temperatures. It is shown that at elevated temperatures T ⪅ Tc the process of magnon absorption on the thermal fluctuations of localized d(f) spins with conduction electron spin flip plays an essential role equally with the process of SW−conduction electron scattering. The results obtained are in qualitative agreement with the experimental data on FMR linewidth.
Deuteration Dependence of the Central Peak in KDP‐Type Ferroelectrics
Authors: Wesselinowa Julia M. 
Published: July 2007

AbstractThe Ising model in a transverse field is treated by means of the Green's function technique to calculate the dynamical structure factor below and above Tc in KDP‐ and DKDP‐type ferroelectrics. Deuteration causes a decreasing in the frequency of the soft‐ferroelectric mode and an increasing in the spin—spin damping. The underdamped character of the soft mode disappears on deuteration. In KD2PO4 the peak around the soft mode is absent and the ferroelectric mode spectra below and above Tc consist only of the central peak around E = 0. All obtained results are in very good agreement with the experimental data.