bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison between the Theoretical and Experimental Electronic Density of States of Liquid Metals
Authors: Halder N. C. 
Published: July 2007

AbstractThe electronic structure and electronic density of states (EDS) are investigated for eleven liquid metals. The theoretical results are obtained from the nonlocal, energy dependent pseudopotentials which reveal some new features not observed previously with the local pseudopotential theory and on Fermi surface approximation. However, a good agreement is found when these theoretical results are compared with the recently available experimental measurements, especially for liquid Cu, Ga, In, Tl, Sn, and Pb.
Valence Band Structure of (Bi1–xSbx)2Te3 Single Crystals
Authors: Stordeur M. , Langhammer H. T. , Sobotta H. , Riede V. 
Published: July 2007

AbstractFor the first time the anisotropy of reflectivity of polarized infrared light of p‐(Bi1–xSbx)2Te3 single crystals (0.5 ≦ x ≦ 1) is given in the wave number range of 300 to 4000 cm−1. In addition to the excitation of free carriers in the reflection spectra of the mixed crystals also interband excitations are observed. For the mixed crystals the optical results are consistently described in terms of a six‐valley band model and scattering on acoustical phonons together with the data for the dc conductivity, the Hall coefficients, and the thermopower. The main axis masses mii, the ellipsoid tilt angle θ, the effective density of states mass m, the cyclotron mass and the susceptibility masses are given in dependence on composition, also the Fermi level EF, the carrier density p, the mobility u⊥c, the high frequency dielectric constant ϵ′∞, and the relaxation time τ. The interband influence is interpreted by a simple band model and the energy gap Eg calculated.
On the Time Dependence of the Capture of Non‐Equilibrium Hopping Charge Carriers
Authors: Esser B. , Zvyagin I. P. 
Published: July 2007

AbstractThe capture of non‐equilibrium carriers hopping between randomly distributed localized states and being trapped by same recombination centres or traps is considered. Exponentially varying transition probabilities between the localized states are assumed. Using a time dependent cluster construction based on the large scatter of the transition probabilities in the system the capture rate R(t) is calculated. R(t) is shown to follow a power‐law dependence, R(t) ∼ t−ξ, where ξ is equal or close to 1.
Electron–Phonon Interaction in Mixed Valence Systems
Authors: Brouers F. , de Menezes O. L. T. 
Published: July 2007

AbstractA Hamiltonian describing mixed valence compounds and including d and f electron–phonon coupling is considered. It is shown that the renormalization of the electronic energy parameters induced by the electron–phonon interaction depends strongly on the nature (static or adiabatic) of the approximation used. The importance of the d electron‐phonon coupling on the narrowing of the f level and the softening of the phonon modes is discussed.
Theory of Secondary Electron Emission. II. Application to Aluminum
Authors: Rösler M. , Brauer W. 
Published: July 2007

AbstractThe theory of secondary electron emission developed in Part I is applied to polycrystalline aluminum and the results are compared with experimental data. The angular distribution of secondary electrons (SE) obtained proves to be a cosine distribution in accordance with measurements. Caused by the V220 model potential coefficient one gets an unrealistic peak at E ≈ 10 eV in the energy distribution of SE. Yield values of SE calculated for primary energies E0 = 1 to 2 keV differ by a factor 1.5 to 2 from the measurements. SE created by plasmon decay contribute nearly 60% to the theoretical yield.
Studies of the Oscillator Strengths of Infrared Vibrational Modes in Glow‐Discharge Hydrogenated Amorphous Silicon
Authors: John P. , Odeh I. M. , Thomas M. J. K. , Tricker M. J. , Wilson J. I. B. 
Published: July 2007

AbstractThe infrared oscillator strengths of the stretching and wagging/rocking modes in glow‐discharge hydrogenated amorphous silicon, a‐Si, is compared to similar data reported recently for sputtered material. For both materials the integrated band intensity of the wagging/rocking mode at 640 cm−1 is proportional to the total hydrogen concentration, NH and is independent of preparation conditions. The derived oscillator strength for the latter mode is identical in glow‐discharge and sputtered a‐Si films. In contrast, the integrated band intensity of the composite silicon‐hydrogen stretching mode is film dependent; the derived average oscillator strength, Γs (2000 + 2100), is significantly smaller in glow‐discharge, compared to sputtered a‐Si. A reanalysis of previous isothermal dehydrogenation data is presented in which Γs (2000 + 2100) is shown to be a function of NH and increases markedly at hydrogen contents < 10 at%. No conclusions can be drawn, however, concerning the oscillator strengths of the deconvoluted bands at 2000 and 2100 cm−1 occurring within the stretching region. A previously proposed model for the mechanism of the dehydrogenation of a‐Si is unaffected by the present results.
Some Remarks on Deviations from Matthiessen's Rule in Dilute Alloy Systems
Authors: Barnard R. D. 
Published: July 2007

AbstractAn examination is made of the main features of deviations from Matthiessen's rule in alloy systems from a general standpoint based on anisotropy in the electron–phonon and electron–impurity scattering. It is shown that in virtually all metals at low temperatures, a T3 or near T3 contribution to the electron–phonon inverse relaxation time exists due to the geometry of the Fermi surface or from U processes which produce large angle scattering. As a result, such metals at low temperatures will possess considerable anisotropy in the electron–phonon mean free paths associated with the transport properties, which arises purely from the geometry of the transitions. It is further shown that the usually small high curvature regions of the Fermi surface which produce the anisotropy, while not making a large contribution to the resistivity of the intrinsically pure metal, however are of paramount importance when impurity scattering dominates and results in near T3 variations of the temperature dependent resistivity, ϱT. Such variations appear to be obeyed almost universally in alloys for which ϱ0≫ϱID. The role of anisotropy in the mean free paths due to gold and dislocations as scattering centres in the silver system is discussed in connection with their failure to adhere to the universal curve of ϱT versus log ϱ0 for silver.
Optical Studies of Er3+ Ions in Er2Ge2O7 Single Crystals
Authors: Yaeger I. , Shuker R. , Wanklyn B. M. 
Published: July 2007

AbstractOptical absorption spectra of Er3+ in Er2Ge2O7 single crystals are studied in the spectral range 14500 to 25000 cm−1 as a function of temperature from ambient down to 12.5 K. The transitions associated with the Er3+ absorption lines are identified. Kramers' doublets of the Er3+ ground term 4I15/2 are found at 13, 88, 125, 185, 230, 392, and 436 cm−1 relative to the ground level.
Evidence of Two Paramagnetic Defects in WO3‐Doped V2O5
Authors: Gaillard B. , Blanchard C. , Deville A. , Livage J. 
Published: July 2007

AbstractThe nature of paramagnetic defects in crystalline V2O5 can be drastically modified by adding very small quantities of doping impurities. Until now, the semiconducting properties of such crystals are interpreted by using a two level hopping model. Spin–lattice relaxation time measurements show that two kinds of paramagnetic defects exist in WO3‐doped V2O5. One is associated with the doping impurity but the other one is not. It corresponds to the intrinsic paramagnetic defects due to the non‐stoichiometry of V2O5.
Exchange Interaction between Paramagnetic Centers and Valence Band Electrons in Semiconductors with Cubic Lattices
Authors: Semenov Yu. G. , Shanina B. D. 
Published: July 2007

AbstractA Hamiltonian is derived for the exchange interaction between paramagnetic ions and electrons from the bands Γ6, Γ7, Γ8, that is the result of the splitting Γ′15, Γ′25, by the spin‐orbit interaction of arbitrary intensity Δso in semiconductors with cubic lattices. It is shown that, Δso being sufficiently large, the Hamiltonian of each splitted subzone is of Heisenberg form. Formulas are derived and numerical estimations are carried out for the exchange interaction constants; the relation of the latter to the crystal band structure is discussed. The sign difference which was discovered experimentally earlier for the constants of exchange coupling between 3d ions and electrons of valence and conduction bands in AIIBVI:Mn2+ crystals is explained by the results of the theory.
Crystal Field of Cr3+ Ion in Spinel Lattice: The Effect of High Hydrostatic Pressure
Authors: Ślawska‐Waniewska A. 
Published: July 2007

AbstractThe crystal field parameters of an octahedral Cr3+ ion in normal and inverse spinel lattices are calculated in the point charge model. As an example LiFe5O8:Cr3+ is considered in more detail. For this spinel the spin Hamiltonian parameter and the one‐ion anisotropy constant of Cr3+ are calculated and compared with experiment. The investigations are extended to include the case of the crystal being under high hydrostatic pressure.
Hopping Conduction and Energy Spectrum of Localized States in low‐Doped Intermediate‐Compensated n‐ZnSe
Authors: Timchenko I. N. , Nedeoglo D. D. 
Published: July 2007

AbstractThe temperature dependence of the resistivity of low‐doped n‐ZnSe crystals with intermediate compensation is investigated in ohmic and non‐ohmic regimes. In the temperature interval from about 20 to 7 K hopping conduction is observed with a constant activation energy, but at lower temperatures the conductivity may be approximated by a dependence of the type In ˜ T−1/2, which may be due to a Coulomb gap in the energy spectrum of localized states. It is found from the non‐ohmic hopping conduction data that the effective length of non‐ohmicity is of the order of the mean inter‐impurity distance and is practically independent of the electric field; the temperature dependence of the effective length (or the percolation threshold) corresponds to the energy spectrum of localized states with a Coulomb gap.
d—s, p Resonance and Electronic Structure of Compounds, Alloys, and Solid Solutions
Authors: Domashevskaya E. P. , Terekhov V. A. 
Published: July 2007

AbstractOn the basis of the valence band structure regularities, obtained from combined X‐ray spectral and X‐ray photoelectron studies of electron energy spectra, a model is suggested for the interaction between valence electrons of s, p‐elements and d‐electrons of IIIA, IIB, IB, and transition metals under the formation of compounds, alloys, and solid solutions, the so called d—s, p resonance. The model qualitatively explains different observed manifestations of state interaction: the energy displacements, subband splitting, mixing of states of different symmetry or, vice versa, pushing of s, p‐states out of the energy interval, occupied by d‐band, due to the mutual energy arrangement of d‐ and s, p‐subbands.
Electron Spin Resonance of Doped Glow‐Discharge Amorphous Silicon
Authors: Dersch H. , Stuke J. , Beichler J. 
Published: July 2007

AbstractThe influence of doping on the ESR spectra of glow‐discharge a‐Si:H is systematically investigated in the X‐ and Q‐band for phosphorus‐ and boron‐doped samples up to a high doping level. Whereas for undoped and moderately doped material the well‐known line with g = 2.0055 is observed, for highly boron‐doped samples the broader line at g = 2.01 predominates as does the g = 2.0043 line in the case of high phosphorus doping. The linewidth of the resonance at g = 2.01, due to holes in localized valence band tail states, is mainly determined by a g‐value spectrum. With increasing boron doping the width of this spectrum decreases and its centre of gravity shifts to smaller g‐values. The narrower line with g = 2.0043, due to electrons in localized conduction band tail states, however, broadens with increasing phosphorus doping due to hyperfine interaction with the phosphorus nuclei. From these features it is concluded that the wave function of holes in valence band tail states is much more localized than that of electrons in the conduction band tail. At the same high doping level the spin density for the hole resonance at g = 2.01 is a factor of about 102 larger than for the electron line with g = 2.0043. This difference is explained by a different correlation energy U. Besides these lines a relatively weak resonance at g = 2.0026 is found for boron‐doped samples and for phosphorus‐doped material as well. Measurements on compensated samples indicate that by doping dangling bonds are created.
Mössbauer Study of the 3d5 Shell Deformation of Fe3+ Ions in MnFe2O4
Authors: Ligenza S. , Kucharski Z. , Suwalski J. 
Published: July 2007

AbstractThe deformation of the 3d5 electron shell of iron atoms in an MnFe2O4 spinel is investigated by means of Mössbauer effect measurements with 60 kOe and without an external magnetic field at 4.2 K. An analysis of ME spectra is carried out using neutron spectroscopy data. It is found that the 3d5 shell deformation observed by neutron spectroscopy brings about the quadrupole splitting 23d = −0.040 mm/s. A change of the charge density at 3d5 electron shell is calculated to be about 0.3%. A dipole magnetic contribution to the effective field on iron ions in octahedral sites, HD, is estimated as +17.6 kOe. The magnitude of all other hyperfine interaction parameters of 57Fe nuclei are also given.
Characteristics of Secondary Electrons Ejected from Solid Targets by Multiply Charged Ions with Energy up to 20 MeV/Nucleon
Authors: Akkermann A. F. , Botvin V. A. , Ya. Chernov G. 
Published: July 2007

AbstractDetailed characteristics of secondary electron emission from silicon after bombardment by multiply charged ions Al, C, O, Ca, Si, Fe with energies up to 20 MeV/nucleon are deduced from Monte‐Carlo simulations. The calculated integral yields η in forward direction to approach the η—Zeff law. The discrepancies between calculated and experimental data for fission fragments are discussed. Limits for ion charge resolution by secondary particle counting are obtained.
Wigner‐Seitz Radius Dependent Model Potential
Authors: Khanna K. N. 
Published: July 2007

AbstractA model pseudopotential for electron‐ion interaction depending on the Wigner‐Seitz radius is proposed for simple metals. The results of individual contributions of binding energy, liquid metal resistivity, phase stability, and electronic charge density obtained from the proposed model potential agree reasonably well with the experimental results for several simple metals.
Effect of Surface Relaxation on Point Defects in the Vicinity of W (100) Surfaces
Authors: Mhaskar S. P. , Naik P. K. 
Published: July 2007

AbstractSurface relaxations of W (100) planes and their effect on point defects are computed with the help of a program that can simulate various processes occurring in the bulk of a solid and in the vicinity of the surface. Formation energies of vacancies and divacancies at various depths from the W (100) surface are calculated. Effect of surface on the activation energies of detrapping reaction of helium from HeV is also investigated. It is observed that formation energies of point defects and activation energies of thermal detrapping reactions continue to decrease approaching the surface from the bulk of a solid.
Effect of Magnetic Quantization on the Diffusivity—Mobility Ratio in n‐Cd3As2
Authors: Chakravarti A. N. , Ghatak K. P. , Dhar A. , Ghosh S. 
Published: July 2007

AbstractAn attempt is made to study the dependence of the diffusivity‐mobility ratio on a quantizing magnetic field in degenerate n‐Cd3As2 in the extreme quantum limit according to the Bodnar model which has recently been shown in the literature to be the most valid model for Cd3As2. The results obtained are then compared to those derived on the basis of the Kane model since many authors have continued to use the Kane model for Cd3As2.
Stability Surface for the Blume‐Capel Model
Authors: Taggart G. B. 
Published: July 2007

AbstractThe stability surface for the Blume‐Capel model is obtained in the thermodynamic space of the temperature and densities (order parameters). This surface, which separates thermodynamically stable (metastable) regions from unstable ones, is determined from divergences in the generalized static susceptibility. The susceptibility itself is derived from correlation functions which are calculated from high temperature expansions to the first order beyond the mean field approximation. Consequently the stability surface exhibits lattice‐dependent effects.
Non‐Γ Deep Levels and the Conduction Band Structure of Ga1−xAlxAs Alloys
Authors: Saxena A. K. 
Published: July 2007

AbstractThe electrical properties of the Ga1−xAlxAs alloys are strongly controlled by the emergence of deep levels in crystals which have x values near to the direct—indirect conduction band transition composition. The activation energy of the deep levels and the energy of the L conduction band minima with respect to the lowest energy Γ minimum (0.19 ≦ x ≦ 0.43) and × minima (0.43 < 〈x ≦ 0.61), are determined from the temperature dependence (77 K ⪅ T ⪅ 750 K) of the Hall electron concentration on high‐purity crystals.It is shown that the lowest energy indirect minima is L in Ga1−xAlxAs for alloy compositions in the range 0.19 ≦ x ≦ 0.37. The variation in the energy separation ΔEΓL at 300 K between the Γ and L minima is best described by the equation ΔEΓL = (0.285 — 0.595x) eV for 0.19 ≦ x ≦ 0.47. The Γ—L cross‐over composition is, thus, determined to be x = 0.47. For x ⪆ 0.25, a deep level dominates the electrical characteristics of the crystals. The activation energy of the deep level with respect to the Γ minimum increases with x, being (0.170 ± 0.005) eV at x = 0.44, but with respect to the L minima remains almost constant with a value of ≤0.200 ± 0.005≤ eV for 0.19 ⪅ x = 0.44. For x > 0.44, the energy of this level below the × minima decreases monotonically reaching a value of (0.106 ± 0.005) eV at x = 0.78. Heavily compensated shallow donor levels are also present in the alloys. Similar measurements on samples with compositions in the range 0.23 ≦ x ≦ 0.32 and under hydrostatic pressure have shown that the deep level is mainly associated with the indirect minima L and × although the Γ minimum is the lowest in energy.
Effective Electron—Electron Interaction in Conjugated Polymers
Authors: Ukrainskii I. I. 
Published: July 2007

AbstractThe excitation energies of charge carriers and neutral excitons in polyacetylene and polydiacetylene are calculated taking into account the electron correlation effects. The singlet exciton band is shown to split off a conduction band if and only if the electron‐electron repulsion on the neighbouring carbon atoms differs from zero. The value of this repulsion is found to be about 3 eV.
Studies by UV and IR Absorption of Particular Motions of NO in Single Crystals of NaNO2
Authors: Jumeau D. 
Published: July 2007

AbstractThe polarization states of the ν2 IR absorption band of NO (ν2 ≈ 828 cm−1 at 20 °C) and of the zero‐phonon line ν00 of the UV electronic transition of NO (ν00 ≈ 385 nm at 10 K), are studied between 10 and 300 K. When the temperature increases, the ν2 (‖b) and ν00(‖a) absorption lines are no longer perfectly polarized along the b‐and a‐axes, respectively, and this depolarization is strongly dependent on the orientation of the wave vector q of the incident light (q ‖ a, b or c). This result may be explained by the NO interaction with low‐frequency waves.
Line Broadening and Line Displacement of EPR Transitions Produced by Inhomogeneous Plane Stresses in a Two‐Layer System
Authors: Gehlhoff W. , Segsa K. H. 
Published: July 2007

AbstractThe strain induced changes of lineshapes and line positions of EPR transitions in a film‐substrate system with elastic cubic symmetry are analysed. Thereby it is assumed, that the distributions of stresses and strains in the two‐layer system are induced by inhomogeneous plane stresses developed in the film.
The Effect of Short‐Range Order on the Vibrational Spectra of 3:2 Coordinated Chalcogenide Glasses. Analysis of the Vibrational Spectra by Using Pyramidal Structural Units
Authors: Giehler M. 
Published: July 2007

AbstractInfrared reflection and Raman spectra of 3:2 coordinated chalcogenide glasses are analysed by fitting the optical spectra using a dielectric function consisting of four oscillator terms. The obtained frequencies and infrared intensities of the major infared and Raman vibrational bands are studied within the framework of one aspect of the short‐range order of 3:2 glasses—pyramidal structural units. It is shown that in this model the frequencies of the major vibrational modes (with the exception of As2O3) of all 3:2 chalcogenide glasses can be well explained if one takes into account chemical trends (i) in the force constants (in such a way that the stretching force constant is inversely proportional to the third power of the bond length) and (ii) in the bond angle of the apex atom of the pyramid (in such a way that an increasing electronegativity of the apex atom with respect to that of the chalcogen atom causes mostly an increase of the bond angle at the apex atom). For an understanding of the major vibrational properties of As2O3 glass the vibrational coupling of the pyramidal stuctural units with each other especially due to the high electronegativity and the light mass of the oxygen atom) must be taken into account. The Penn gap energies and ionicities of 3:2 coordinated chalcogenide glasses are determined within the approximation that each pyramidal structural unit contributes eleven valence (including lone‐pair) electrons to the chemical bonding. The chemical trend in the intensities of the major infrared vibrational bands characterized by the effective charges is explained as due to a trend in the ionicities of the studied glasses.
Jahn‐Teller Effect in Narrow‐Band Cubic Crystals with E‐Type Ground State
Authors: Mironov V. S. , Ionova G. V. , Groznov I. N. , Ionov S. P. 
Published: July 2007

AbstractThe cooperative Jahn‐Teller effect in narrow‐band three‐dimensional crystals of cubic symmetry perovskite (AMX3) or ReO3‐type structure is considered. A transition metal ion with E ground state in a crystal field of cubic symmetry is treated. The number of band electrons per ion ranges between 0 and 4. The electronic correlations are neglected. The static Jahn‐Teller distortions of the crystal at T equals; 0 K as well as the electronic structure and possible types of orbital ordering are determined. The cooperative Jahn‐Teller effect in band crystals is shown to lead to charge order (besides orbital order). This orbital‐charge ordering is not connected with electronic correlation.
Phonon Widths in RbBr at 80, 290, and 370 K from Neutron Measurements
Authors: Nilsson G. G. 
Published: July 2007

AbstractNeutron inelastic scattering experiments are performed on RbBr at 80, 290, and 370 K and the experimental phonon widths are determined. Very little broadening with temperature is observed except for certain longitudinal optical modes which are broad at all temperatures and also show a marked temperature dependence in the width. A comparison is made with infrared data where measurements on the fundamental absorption peak yield information about the phonon width.