bluuebunny/crossref_metadata_2025_split huggingface dataset:
Approximate Calculation of Inner‐Shell Binding Energies and Auger Transition Energies of Solid Silicon Compounds
Authors: Zwanziger C. , Petrowa S. , Reinhold J. , Streubel P. , Meisel A. 
Published: July 2007

AbstractUp to now the extended Fenske‐Hall LCAO method (EFH method) has been used to calculate approximately the inner‐shell binding energies and their chemical shifts for a variety of inorganic and organic molecules. In this paper the first attempt is made to test the EFH method for solids. First results are given for silicon and some of its compounds (SiC, Si3N4, SiO2, Na2SiF6). The solids are modeled by clusters saturated by hydrogen‐type pseudoatoms. For these clusters the inner‐shell binding energies Si 1s and Si 2p as well as the Auger energies KLL are calculated. A reasonably good agreement of the calculated chemical shifts of the 1s, 2p, and KLL energies with experimental data of the solid surfaces can be noted. Furthermore, one can predict the order of magnitude of the relaxation energies.
Galvanomagnetic Properties of p‐Hg1−xCdxTe
Authors: Höschl P. , Moravec P. , Prosser V. , Szöcs V. , Grill R. 
Published: July 2007

AbstractA three‐level model for one divalent acceptor (Hg vacancy) and one monovalent acceptor (foreign atom) is suggested. The hole mobility is determined for p‐like wave functions (polar phonons and ionized impurities). Low temperature (10 to 300 K) galvanomagnetic measurements of undoped p‐Hg1−xCdxTe (x ≈ 0.2) are reported. A simultaneous analysis of the hole concentration and Hall mobility data in the region 10 to 100 K and Hall coefficient and conductivity data in the region 100 to 300 K yield ionization energies of ≈ 6 meV and ≈ 0.7 Eg (energy gap) for the Hg vacancy and ≈ 12 meV for the foreign acceptor. In the temperature region 100 to 300 K the mobility of electrons is determined, too.
NMR Study of the Zinc Chalcogenides (ZnX, X = O, S, Se, Te)
Authors: Bastow T. J. , Stuart S. N. 
Published: July 2007

AbstractA nuclear magnetic resonance investigation of the solid zinc chalcogenides ZnX (X = O, S, Se, Te) is carried out, using the following nuclei as probes, 67Zn, 17O, 33S, 77Se, and 125Te. The spectra yield nuclear quadrupole coupling constants and chemical‐shift parameters for polycrystalline ZnO and Zns in the wurtzite (hexagonal) form, and chemical shifts and linewidths for polycrystalline ZnS, ZnSe, and ZnTe in the sphalerite (cubic) form. A single crystal of ZnO is used to obtain an accurate measurement of the quadrupole coupling constant for 67Zn, ∣e2qQ/h∣ = 2.4065(15) MHz at 296 K, in agreement with a recent Mössbauer‐effect measurement. The electric field gradient of the wurtzite structures is analysed with a simple ionic model, and the results are found to be in semi‐quantitative agreement with experiment.
Linear Birefringence Investigations of the Jahn‐Teller Distorted Phase in the Mixed Crystal Systems (Tbx, Tm1−x)VO4 and (Tbx, Yb1−x)VO4
Authors: Pilawa B. , Hess G. , Kahle H. G. , Kasten A. 
Published: July 2007

AbstractMeasurements of the linear birefringence in the distorted phase of (Tb, Tm)VO4 and (Tb, Yb)VO4 crystals allow to separately establish the contributions of the individual rare‐earth ions and the anion complex for the first time. By this, the dissimilar wavelength dependence of the birefringence in pure Tb and Tm vanadate can be understood. A mean field theory including random‐strain effects is used to treat the distorted phase and to elucidate the absence of the Jahn‐Teller phase transition at low Tb concentrations.
Positron Annihilation Studies in Zeolites
Authors: Dębowska M. , Abbé J. Ch. , Duplâtre G. 
Published: July 2007

AbstractPositron annihilation experiments using both lifetime spectroscopy and Doppler broadening of the annihilation lineshape technique are performed for various pure zeolites and for mordenite impregnated with highly dispersed gold particles. Changes in the annihilation parameters are tentatively correlated with the properties of the samples and, in case of impregnated samples, attributed to the presence of gold particles in the matrix of the zeolite.
Influence of a vVacancy on Luminescence of Pb+ Centres in Alkali Halides
Authors: Nagli L. E. , Dyachenko S. V. 
Published: July 2007

AbstractLuminescence of Pb+ centres in X‐irradiated Pb2+ doped KCl, KBr, and KI crystals is first observed at 1.29, 1.21, and 1.14 eV, respectively. It is excited in the bands of KCl:Pb2+ at 4.93, 4.45, 3.70, 2.03 eV, of KBr:Pb2+ at 5.20, 4.55, 4.20, 3.20, and at 5.10, 4.30, 3.91, 3.52, 3.02, eV for KI:Pb2+. The effect is studied of the presence of the cation vacancy on both, the excitation and emission spectra of the Pb+ centre. Temperature, kinetic, and polarization characteristics of Pb+ and Pb+vc−‐centres in KCl:Pb2+ are investigated.
Picosecond Transient Optical Nonlinearities in CdS and CdSSe
Authors: Egorov V. D. , Flögel P. , Nguyen Hoang Xuan , Kaschke M. 
Published: July 2007

AbstractNonlinear absorption of CdS and CdS0.7Se0.3 crystals is studied around room temperature using an excite‐and‐probe technique in the ps time region and taking Fabry‐Perot interferences into account. Large nonlinear changes of the optical coefficients are obtained. The experimental spectra are in reasonable agreement with the theoretical ones assuming a heating of the excited carriers. The nonlinearities relax within about 1 ns.
A New Empirical Two‐Body Interaction Potential Fitted to Second‐ and Third‐Order Elastic Moduli
Authors: de Graff M. , Delaey L. 
Published: July 2007

AbstractA new empirical model for an interatomic pair potential is derived, allowing for a full fit of second‐and third‐order elastic moduli. First the general equations, valid for any crystal class, are derived. These equations are then applied to the body centered cubic and the face centered cubic structures; the potential derivatives are then expressed as linear combinations of the elastic moduli. Introducing a number of free parameters (e.g. potential depth, core slope,…) the potential can be constructed as a set of fourth order piecewise continuous splines. Some examples are also given to illustrate the effect of changes in the fitting parameters. Finally the applicability of the new model is briefly discussed.
Thermodynamics of Defect Formation and Defect Interaction in Compound Semiconductors
Authors: Bulyarskii S. V. , Oleinikov V. P. 
Published: July 2007

AbstractBased on the Gibbs cannonical distribution, a number of physical quantities is related to crystal growing conditions such as various point defect densities (intrinsic, vacancies, antistructural, complex of some point defects), high‐temperature density of free carriers, homogeneity region width, and impurity distribution factor. It is discussed how to calculate the Gibbs partial potential from experimental data. The results can be now used for solving a variety of problems of point defects in semiconductors including effects of complex formation.
Phonon–Phonon Interaction in Gadolinium–Gallium Garnet Crystals
Authors: Kleszczewski Z. , Bodzenta J. 
Published: July 2007

AbstractPropagation velocity and temperature dependence of the sound wave attentuation coefficient in gadolinium–gallium garnet crystals are measured. The measurements are carried out in the frequency range 0.4 to 2.0 GHz and temperature range 77 to 293 K. On the basis of the measurements Debye temperature, specific heat of crystal as a function of temperature, and the temperature dependence of thermal phonon lifetime are determined. For calculation it is assumed that the examined material is isotropic.
Non‐Linear Light Absorption Spectroscopy in Sb–S–I Crystals and Glasses
Authors: Lisitsa M. P. , Turyanitsa I. D. , Fekeshgazi I. V. 
Published: July 2007

AbstractThe spectral dependence of the two‐photon induced linear light absorption in Sb–S–I crystals and glasses are studied. An allowed–forbidden character of the two‐photon transitions and the spectral pecularities due to two‐step transitions through real energetic levels are found.
Thermoluminescence and Fluorescence Studies on RbBr:Gd2+
Authors: Sastry S. B. S. , Muralidharan G. 
Published: July 2007

AbstractTL glow of γ‐irradiated crystals shows a single peak at 380 K. On F‐light bleaching a new peak attributable to Z1‐centres appears around 355 K. The presence of OH− reduces the TL glow. The characteristic emission of the impurity is observed at 3.65 eV. The irradiated crystals show the presence of the “O2−–vacancy” complex. The TL process is due to the thermal release of F‐electrons.
Analysis of Crystal Binding and Thermoelastic Properties of Cuprous Halides, Silver Halides, and Thallous Halides
Authors: Chaturvedi S. D. , Dixit R. C. , Sangachin A. A. S. 
Published: July 2007

AbstractCrystals of cuprous halides, silver halides, and thallous halides are found to show significantly different behaviour from that of alkali halides. This difference is mainly due to the presence of outermost d‐electrons present in Cu+, Ag+, and Tl+ ions. In the present paper an analytical potential form is used for the overlap repulsive energy derived by Harrison from quantum mechanical considerations. The parameters in this potential form have direct correlation with the valence state energies for outermost d‐electrons. The potential model is applied to calculate the cohesive energies, pressure derivatives of bulk modulus, Grüneisen parameter and its volume dependence using different existing theories.
Image Potentials and Image Forces in the Polaron Theory
Authors: Pokatilov E. P. , Beril S. I. , Fomin V. M. 
Published: July 2007

AbstractA polaronic approach for the problem of image force potential is developed. Within this approach dispersion of the dielectric constant and electron recoil effects are taken into account. For the semiconductor‐vacuum interface at small values of electron effective mass and high values of semiconductor dielectric constant the electron recoil is found to cause a greater reduction of the potential than the dispersion of dielectric constant, and to play the main role in cutting off the singularities of the image force potential. Analytic formulae for the image force potential energy are obtained accounting for the electron recoil effects and ignoring the dispersion. The coordinate dependences of this potential in vacuum and in medium are analyzed.
Excitonic Processes and Thermoluminescence in NaCl Crystals Doped with Mg or Mn
Authors: Egranov A. V. , Nepomnyachikh A. I. 
Published: July 2007

AbstractProcesses of defect creation by VUV‐excitation are studied by the thermoluminescence method. NaCl crystals doped with Mg or Mn are irradiated at 80 K by monochromatic VUV‐light in the region of 7 to 8 eV. Excitation spectra of the glow peaks at 195 K (NaCl‐Mg) and 220 K (NaCl‐Mn) have maxima at 7.5 and 7.4 eV, respectively. It is concluded that the TL excitation spectra correspond to the formation of an exciton near the divalent metal (Mg2+ or Mn2+) of the impurityvacancy complex. The decay of these excitons leads to formation α‐Iz pairs at 80 K.
On a Theory of the Electronic Spectrum and Magnetic Properties of High‐Tc Superconductors
Authors: Gaididei Yu. B. , Loktev V. M. 
Published: July 2007

AbstractAn attempt is made to derive consistently the Hamiltonian of electron excitations of high‐Tc superconductors (HTSC) proceeding from their ionic and crystal structure. The carriers are shown to be able to move both, over the copper and oxygen subsystems. The spectrum of free (excess) carriers is found. It is established that the Jahn‐Teller (two‐level) character of Cu2+ results in a specific pairing mechanism being the most effective in rhombically distorted lattices. The analogy between HTSC and Kondo lattices (or in some sense heavy‐fermion systems) is traced and the possible reason of suppressing magnetism and breaking the magnetic order in HTSC is discussed.
Er2O2SO4 — An Ising System with Six Magnetic Phases
Authors: Mayr A. , Paul W. , Kahle H. G. 
Published: July 2007

AbstractAt low temperatures, Er2O2SO4 orders as an Ising antiferromagnet with moments along the crystallographic c‐axis. Measurements of the magnetisation in zero magnetic field show two anomalies at T N1 = 1.58 K and TN2 = 1.54 K, indicating two different ordered phases. In external fields applied along the easy axis, three ferrimagnetic phases with fractions 1/4, 1/3, and 1/2 of the saturation magnetisation are traversed before the saturated paramagnetic state is reached. The spin structures of the different phases are discussed on the basis of topological considerations developed by Kanamori.
A Global Cut‐and‐Project Method to Construct Generalized Fibonacci Lattices and Quasilattices
Authors: You J. Q. , Hu T. B. 
Published: July 2007

AbstractA global cut‐and‐project method is developed. By this technique, the construction is discussed of aperiodic lattices including both, generalized Fibonacci lattices and octagonal, decagonal, and dodecagonal quasilattices. Diffraction patterns with 8‐, 10‐, and 12‐fold symmetries are simulated, which agree well with the experimental results. A modulation is introduced to explain the two alternating sets of periodic layers along the 10‐fold axis in the diffraction pattern of decagonal quasicrystal.
Relations between Structure, Bonding, and Nature of Point Defects in Layered Crystals of Tetradymite Structure
Authors: Horák J. , Starý Z. , Klikorka J. 
Published: July 2007

AbstractA quantum chemical calculation of bonding parameters in Sb2Te3, Bi2Te3, Bi2−xInxTe3, and Bi2Te3−xSx single crystals is carried out. The electric conductivity σ ⟂ c and Hall constant RH(B ∥︁ c) of the crystals in the Bi2Tes−xSx system are measured. These results present a basis for the discussion of the different role of impurities in anion and cation sublattices with respect to the bonding parameters and the concentration of anti‐site defects in the Bi2Te3−xSx system is calculated and compared with the formation energy of the same defects in the Bi2−xInxTe3 system.
Etude de l'évolution avec la température des modes actifs en diffusion Raman du ZnF2
Authors: Giordano J. , Sauvajol J. L. 
Published: July 2007

AbstractLes évolutions de fréquences et des largeurs des modes actifs en diffusion Raman du fluorure de zinc ont été mesurées entre 4,2 et 300 K. Les contributions au glissement en fréquence liées à la dilatation volumique et à l'anharmonicité ont été évaluées pour chaque mode Raman. II a été misen évidence un amollissement du mode B1g avec la température. L'utilisation d'un modèle à ions rigides permet de relier l'évolution en température des constantes élastique du ZnF2 aux évolutions des fréquences Raman. Tous les résultats obtenus en utilisant différentes techniques expérimentales (Raman, IR, mesures de constantes élastiques) permettent d'envisager la tendance à la mise en place d'un ordre ferroélectrique à basse température. Nos résultats sont discutés et comparés avec ceux obtenus dans le cas de certains fluorures et oxydes métalliques de měme structure que ZnF2.
Positronium at Metal Surfaces
Authors: Shrivastava S. B. , Gupta V. K. , Bhadoriya K. S. 
Published: July 2007

AbstractBased upon rate equation approach and considering the positron trapping in image potential a semiquantitative model is proposed to obtain the fraction of positronium formation at metal surfaces. Ps fractions are calculated for the surfaces of Cu(100), Ag(100), and Ag(111) and are compared with the experimental results. The results in Cu(100) and Ag(100) are in good agreement with the experiments, however, in case of Ag(111) these are underestimated at low temperatures.
Calculated Fermi Surface Characteristics of the Noble Metals
Authors: Graefenstein J. , Mertig I. , Mrosan E. , Antonov V. N. , Antonov Vl. N. 
Published: July 2007

AbstractSome Fermi surface characteristics are calculated like the optical mass, the cyclotron masses, and the Fermi velocities of the noble metals. The underlying selfconsistent energy bands are obtained by means of a nonrelativistic KKR method for Cu and Ag and by means of a relativistic LMTO method for Au. The estimated optical masses agree satisfactorily with data from optical experiments. Taking into account the electron–phonon renormalization of the experimental data, the calculated cyclotron masses and anisotropic Fermi velocities agree well with de Haas‐van Alphen and magnetic field induced surface state resonance results. From the comparison of the theoretically and experimentally derived Fermi velocities the anisotropy of the electron‐phonon enhancement factor λ(k) is determined for Cu and Au.
About the F Center in Cesium Halides
Authors: Ruiz‐Mejía C. 
Published: July 2007

AbstractThe energy levels for the F center in cesium halides are determined. The point ion method and the ion size correction are applied. Vacancy‐centered trial wave functions of three types are used. The structure of NaCl and the CsCl are considered in the calculations. It is concluded that some investigations probably used the NaCl structure in their calculations for cesium halides. For wave functions of the Gourary‐Adrian type it is found that the Bartram et al. method can not be applied for values of the empirical parameter α ≧ 0.53. Others papers are discussed.
Deviations from Matthiessen's Rule in Ag;Au Alloys
Authors: Tiwari M. D. , Thummes G. , Kukermann V. 
Published: July 2007

AbstractAn experimental and theoretical study is made of electrical transport in dilute Ag‐based alloys with the view to understand the observed deviations from Matthiessen's rule. Various concentrations of gold are doped in silver. The measurements are extended to higher temperatures. A scattering‐time solution to the Boltzmann transport equation is employed. The anisotropy in the scattering is fully accounted for since it is known to be an important mechanism for deviations from Matthiessen's rule. Also included are the dynamical nature of the impurity, the interference between the impurity and the perfect‐crystal scattering, and the effects of mass‐change and force‐constant‐changes. Further, the role of the Debye‐Waller factor is discussed.
Thermal Expansion, Heat of Fusion, and Electron Density of Monovalent Metals
Authors: Mimkes J. 
Published: July 2007

AbstractThe enthalpy of monovalent metals is calculated as a function of electron density according to the model of nearly free electrons. The coefficient of thermal expansion of solid and liquid monovalent metals is given by heat capacity and Fermi energy, αP(T) = 2.5 × CP(T)/ϵF(T). The heat of fusion is determined by Fermi energy and relative change in volume at the melting point, Lm = 0.4ϵF(Tm) × (VL − VS)/VL. The agreement with experimental data is quite satisfactory for all alkali and noble metals.
Finite Motion of Microparticles in Tunnel‐Effect Multiquantum Well Structures
Authors: Volkov R. A. , Chuiko A. F. 
Published: July 2007

AbstractA perturbation theory is developed for calculating eigenenergies (EE) and wave functions (WF) of a microparticle localized in a multiquantum well (MQW) semiconductor structure. Elastic tunnellings of one charge carrier and many charge carriers between quantum wells (QW) of arbitrary smooth shape are investigated. It is concluded that non‐decaying periodic currents can arise in the above structure. Analytical expressions are obtained for such currents and for times of tunnelling across the barriers of a set of QWs. Many‐particle tunnellings in a sawtooth double‐QW structure are considered.
Effect of a Tilted Magnetic Field on the Size‐Quantized Levels of Quantum Wells in Ultrathin Films of Narrow‐Gap Semiconductors
Authors: Bose M. K. , Majumdar C. , Maity A. B. , Chakravarti A. N. 
Published: July 2007

AbstractAn attempt is made to investigate the effects of a tilted magnetic field on the size‐quantized levels of quantum wells in ultrathin films of narrow‐gap semiconductors, taking n‐type InSb as an example. It is found that, in general, the energy eigenvalue of the lowest magneto‐size‐quantized level increases with increasing magnetic field and decreases both, with increasing film thickness and with increasing orientation of the magnetic field, for given values of the other parameters. Besides, it is observed that the difference of the energy eigenvalues of the lowest two magnetic sub‐levels of the lowest electric sub‐band reaches a maximum at a given magnetic field, showing a decrease with its orientation, while it increases with the film thickness.
Electronic Structure of Pd1−xNix Alloys Investigated by Positron Annihilation
Authors: Dębowska E. , Rudzińska‐Girulska J. 
Published: July 2007

AbstractThe entire concentration range of α‐phase Pd1−xNix alloys is studied by angular correlation and positron lifetime methods. The electron number per one alloy atom is analyzed and the progressive delocalization of d‐like electrons with increasing Ni concentration is postulated. Attention is also paid to the problem of annihilation rate in alloys. The changes in the character of annihilation parameter dependences on x are seemed to be connected with para‐ to ferromagnetic transition.
Dynamics in the System of Dipolar Impurity Centers in Crystals
Authors: Bersuker G. I. 
Published: July 2007

AbstractA model is proposed for the description of the dynamics in the system of dipolar impurities in crystals. The impurities are assumed to reorient by the Arrhenius temperature dependence in the case when the activation energy is much larger than the temperature of reorientation freezing (the temperature of the phase transition in the impurity subsystem). The reorientation is caused by the transitions between the localized (in the minima of the adiabatic potential) and excited delocalized states of the impurity induced by one‐phonon processes (the multiphonon ones are ineffective at the low temperatures under consideration). The freezing of the reorientation at each center takes place at temperatures, at which the energy gap between the effectively populated localized state and the delocalized one becomes larger than the maximum frequency of the crystalline phonons. The rise of the impurity concentration increases the phonon‐exchange interaction between the near‐neighbor centers during their reorientation, resulting in the increase of the energy of the delocalized state, and hence in the increase of the freezing temperature of the dipole dynamics. In the framework of this approach the system of Li+:KTaO3, is considered as an example.
Theory of Superconductors with Strong Coupling in the Bogolyubov Method
Authors: Lozovsky V. Z. , Nazarenko A. B. , Khudik B. I. 
Published: July 2007

AbstractThe Bogolyubov U–V transformation method is generalized to the diagonalization of an electron–phonon Hamiltonian in the superconducting medium. The self‐consistent equations are written. The structure of the quasi‐particle spectrum is found. The criterium of superconductivity is discussed.
Magnetic Freeze‐Out and Magnetic‐Field‐Induced Semiconductor–Semimetal Transition in Bi1−xSbx Alloys under High Hydrostatic Pressure
Authors: Kraak W. , Troppenz U. , Herrmann R. , Chudinov S. M. , Kulbachinskii V. A. 
Published: July 2007

AbstractThe galvanomagnetic properties of extremely pure single‐crystal Bi1−xSbx alloys (x ≈ 0.07 to 0.08) are investigated under hydrostatic pressure with static magnetic fields in the range 0 to 6 T. A striking anomalous behaviour of the longitudinal magnetoresistance (B ∥ C3) is observed in pure crystals (n < 1014 cm−3) which occurs as the magnetic field is increased above a certain critical value. At low magnetic fields and at high magnetic fields the electrical resistivity increases with increasing temperature in a metallic manner in contrast to the thermally activated behaviour observed at intermediate fields. A strong enhancement of the observed anomalies under hydrostatic pressure is found. An analysis of the results shows that the anomalous properties are associated with charge carrier freeze‐out effect in the intermediate field regime and a magnetic‐field‐induced semiconductor–semimetal transition in high magnetic fields. A simple schematic diagram of the band‐edge and impurity–level configuration of Bi1−xSbx alloys is proposed to describe the found experimental data.