bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soft X‐Ray Emission Spectra from Some NiAl Alloys
Authors: Maslenkov S. B. , Kozlenkov A. I. , Filin S. A. , Shulgin A. I. 
Published: July 2007

AbstractA new effective method of electron microprobe grating spectroscopy is applied to the experimental investigation of the Al L2,3 (+ Ni M2,3) emission band of some nickel‐aluminium alloys. The compositional (or structural) changes in the spectra are compared with the theoretical band structure and X‐ray intensity calculations. The observed variations in the spectrum profile may be attributed to the charge transfer between the component atoms and the hybridization of s and d electronic states in the valence band.
XPS and XES Study of the Valence Band of Cr‐Al B.C.C. Solid Solutions
Authors: Ławniczak‐Jabłońska K. , Minni E. , Pełka J. , Suoninen E. , Auleytner J. 
Published: July 2007

AbstractThe XPS and Cr Lα ES valence band spectra of b.c.c. Cr‐Al alloys in the region 0 to 25 at% Al are presented. The shape and halfwidth of these spectra change notably at approximately 15 at% Al. The results are discussed on the basis of various simple models for the electronic structure of the alloys. The observed changes in the valence band are consistent with the results of magnetic and resistivity measurements. However, the present understanding of the changes in the electronic structure of the Cr‐Al alloys is not complete. The effect of the recently discovered inhomogeneity of the microstructure of these alloys in the upper part of the concentration region upon the electronic structure is, together with the antiferromagnetic order, the probable reason for the observed complicated behaviour of the valence band spectra with composition.
To the Theoretical Explanation of the “Universal Response”
Authors: Nigmatullin R. R. 
Published: July 2007

AbstractThe observation of a universal response of electromagnetic, acoustic, and mechanical influences shows the existence of some transfer processes in a medium, which are not described by a usual diffusion equation. It is shown that these processes can be explained by making use of the diffusion equation taking into account the ‘non‐Marcovian’ character of the excitation transfer process. In accordance with the experimental data a memory function is found which in one limiting case describes pure diffusion (absence of memory) and in another case turns into the wave equation (full memory). A local field frequency distribution function is suggested which confirms the suppositions made. The conditions of the realisation of the transfer process with ‘remnant’ memory are found and described by a generalized linear transfer equations in fractional derivations.
Calculation of the Intensity of the Small‐Angle X‐Ray Scattering by Small Clusters of Intrinsic Point Defects
Authors: Kienle W. , Frank W. 
Published: July 2007

AbstractThe small‐angle X‐ray intensity scattered by small platelet‐shaped agglomerates of vacancy or self‐interstitial type is calculated in two ways: within the framework of continuum theory or by a discrete‐lattice model. Both the methods take into account that small clusters are not fully relaxed. A comparison of the numerical results of the two methods is presented for copper. It is found that both the methods lead to results which considerably deviate from those obtained for completely relaxed clusters.
Effective Hamiltonian for the Two‐Dimensional Arbitrary Spin Ising Model
Authors: Sznajd J. 
Published: July 2007

AbstractA method of the reduction of the generalized arbitrary spin two‐dimensional Ising model to the spin‐half Ising model is presented. The method is demonstrated in detail by calculating the effective interaction constants to the third order in a cumulant expansion for the triangular spin‐one Ising model (the Blume‐Emery‐Griffiths model).
Optical Absorption in Neutron Irradiated GaAs
Authors: Baramidze N. V. , Bonch‐bruevich V. L. , Kurdiani N. I. 
Published: July 2007

AbstractThe spectral dependence is investigated of the light absorption coefficient, α, of GaAs subjected to a fast‐neutron irradiation. In the tail region a complex dependence is found: three parts are seen each of which is described by an exponential dependence of α on photon energy. The experimental results are explained using the concept of random fieldsgenerated by irradiation produced clusters. The statistical characteristicsof the fields are calculated and a quantitative agreement with the experimental data is obtained. Various parts of the spectrum are ascribed to absorption tails due to three kinds of random fields: 1. a deformation potential field due to cluster produced stresses, 2. a smooth field produced by a setof charged clusters in the GaAs matrix, and 3. an intrinsic random field inthe amorphous substance of the clusters.
Impurity Charge Screening in 3d Alloys
Authors: Cser L. , Gladkih I. , Hargitai C. 
Published: July 2007

AbstractThe change of isomer shift and hyperfine field in the first coordination shell of impurity atoms in iron‐based 3d‐metal alloys is discussed from the viewpoint of different charge screening models. It is shown that the change of isomer shift can exactly be described in terms of the asymptotic Friedel model. Interpretation of the hyperfine field change is more difficult and several different models are considered.
Critical Analysis of the Excitation Map Concept for Studying Threshold Effects in VLEED
Authors: Lopez J. , Le Bossé J. C. , Baudoing R. 
Published: July 2007

AbstractThe excitation map concept introduced by Solbrig to discuss threshold effects in very low energy electron diffraction (VLEED) is reinvestigated. In detail the relevance of such excitation maps (| det (1 — M−+R+−)| where M−+ is the reflection matrix of the atomic planes and R+− is the internal reflection matrixof the surface barrier) for characterizing surface resonances in VLEED is examined. It is shown that, in most cases, the use of this concept leads to an overestimate of the resonance contribution in VLEED spectra. The excitation map concept is replaced by a new relevant one. This result is exemplified by reinvestigating the region of Solbrig's excitation map on Ni(001) corresponding to the normal incidence, just below the emergence of the first four diffracted beams (10), (01), (10), and (01). Even in this case, in favour of the resonance interpretation according to Solbrig's analysis, it is shown that the picture of a waveguide located at the surface, channelling the pre‐emergent waves, falls down. This conclusion is strengthened by an analysis of the reflection amplitude matrix of the crystal based upon a second‐order expansion in which the actual role played by resonances can be easily examined. In the case of Ni(001), threshold effects are only due to a simple interference process.
The Voigt Effect under a Strong Electric Field in Semiconductors
Authors: Stramska H. 
Published: July 2007

AbstractThe nonlinear Boltzmann equation is discussed for a strong dc and weak ac electric field. The addition of an energy relaxation approximation to the Boltzmann equation provides analytical expressions for the magneto‐conductivity in high dc electric fields. The nonlinear current density is derived for a strongly degenerate electron gas and for a nondegenerate electron gas. The free carrier Voigt effect in the presence of a strong dc electric field is calculated.
Structure and Vibrational Spectra of a Model of a‐Si:H with Periodic Boundary Conditions
Authors: Winer K. , Wooten F. 
Published: July 2007

AbstractA ball‐and‐stick model of a‐Si:H with periodic boundary conditions is constructed. A computer replica of the structure is relaxed and the density, radial distribution function, and vibrational spectracalculated.
Solution Enthalpies of Divalent Defects in Alkali Fluorides and Chlorides
Authors: Bandyopadhyay S. , Deb S. K. 
Published: July 2007

AbstractA method is suggested for finding the Born‐Mayer repulsive parameters of a divalent defect cation in an alkali halide crystal, from the charge density overlap of the interacting ions. These parameters are utilised to calculate the heat of formation of dilute solid solutions of CaCl2, SrCl2 in each of the three alkali chlorides NaCl, KCl, and RbCl and those of CaF2, SrF2 in each of the three alkali fluorides NaF, KF, and RbF following the standard procedure of minimising the lattice energy numerically, as a function of the relaxation of the nearest neighbours, when the defect cation occupies a substitutional position. As known that the calculation of the heat of formation of solid solutions is very sensitive to the proper choice of the repulsive parameters, so these physically plausible calculated values suggest the validity of the method forfinding the solution enthalpies of divalent defects in alkali halides.
An Analytical Theory of FMR in Bulk Metals (Parallel Configuration) III. Surface Impedance
Authors: Fraitová D. 
Published: July 2007

AbstractA solution of the surface conditions of a ferromagnetic bulk metal for the region of ferromagnetic resonance is presented; the sample in the form of a flat disc is statically magnetized in its surface plane. The assumption of pinned surface magnetization motion (with arbitrary value of uniaxial surface anisotropy parameter and axis normal to the sample surface) is included. The general formulae for the surface impedance are deduced, which agree with the exact numerical calculations of better than 2%.
Mode—Mode Coupling Effects in the Singlet—Triplet Paramagnet in the Vicinity of the Curie Point
Authors: Kowalewski L. , Wojciechowski R. 
Published: July 2007

AbstractWithin the Mori approach the magnetic longitudinal relaxation function in the singlet—triplet model near the Curie temperature is analysed. The influence of mode—mode coupling effects, especially of those of transverse intratriplet excitations, on the long‐time tail of relaxation function and on the line shape of the central mode is also discussed.
Multiple Scattering of Relativistic Electrons under Axial Channeling ina Crystal Model of the Lattice of the Atomic Rows
Authors: Taratin A. M. , Vorobev S. A. 
Published: July 2007

AbstractUsing computer simulation and the lattice model of atomic rows the evolution of the ultrarelativistic electron flux under channeling in the <111> direction in a silicon crystal due to multiple scattering by crystal electrons and nuclei is investigated. It is shown that the electron subtrapping in the bound states takes place in the crystal volume together with the electron dechanneling from the bound states with the atomic rows. A fraction of the particles undergoing the volume trapping is singled out for the first time, and its thickness and orientational dependences are obtained.
Low‐Energy Electron Reflection Intensities from 2HMoS2 as Derived by Scattering Matrix Calculations
Authors: Smith A. E. , Lynch D. F. 
Published: July 2007

AbstractResults of scattering matrix calculations for the reflection intensities of low energy electrons in the range 0.25 to 15.75 eV are displayed for the layered transition metal dichalcogenide 2HMoS2. An incident energy‐dependent absorption potential based on energy loss data is used. The variation of signal with incident angle is explored and comparisons are made with experimental total current measurements. As with previous work it is concluded that the crystal structure determines the intensity spectrum and that a precise description of the individual scattering events is not necessary.
A Simple Muffin‐Tin Model for Liquid Metals
Authors: Vasvári B. 
Published: July 2007

AbstractAn approximation is developed to the scattering path operator for a topologically disordered system of muffin‐tin potentials. Using the multiple scattering Green's function formalism a simple expression is obtained for the local density of states (LDOS). A heuristic type of averagingprocedure can be chosen which leads to non‐negative LDOS in the conduction band. Numerical results are presented for an s‐resonance model and for liquid 3d transition metals using a self‐consistent crystalline muffin‐tin potential and experimental pair distribution function.
The Absorption Spectrum of Manganate (VI) in BaSO4. A Reinterpretation
Authors: Borromei R. , Oleari L. , Day P. 
Published: July 2007

AbstractThe polarised electronic spectrum of MnO2−4 doped in crystals of BaSO4 is re‐interpreted by making a detailed comparison with the corresponding spectra in the host lattices M2SO4 (M  K, Rb, Cs) and K2CrO4. All bands above 16500 cm−1 arise from charge transfer transitions while the part of the spectrum below 16500 cm−1 is due to theligand field transition e → 2t2. Moreover in BaSO4 the ligand field excited state 2T2(e → 2t2) undergoes a large splitting due to the site perturbation in contrast to K2SO4 in which the splitting is very small. The energies of the charge transfer excited states are only slightly affected by the changeof host lattice. With the new assignments all the ligand field and charge transfer spectra of the d1 tetroxo‐anions MnO2− and CrO3−4 can be interpreted in terms of a common scheme.
Similarity of Ground‐ and Excited‐State Absorption Spectra of Cr3+ Ions in a Strong Crystal Field
Authors: Veremeichik T. F. 
Published: July 2007

AbstractA comparative analysis of the broad bands of the ground‐ and excited‐state absorption spectra of d3‐impurity ions iscarried out in a point‐ion crystal field theory model. It is found that for d3 electrons in the cubic field (d7 in tetrahedral field) a similarity of these bands should be expected. The similarity results from the particular symmetry of the initial terms of the compared transitions (these terms correspond to the t32 half‐filled shell of the strong cubic field) and from the same orbital symmetry ofthe final state wave functions. Theoretical conclusions are applied to the experimental spectra of Cr3+ ions in ruby, emerald, and MgO. The use of the similarity of ground‐ and excited‐absorption spectra is suggested. The same analysis is carried out for the d2 configuration as well.
Low‐Temperature Lattice Thermal Conductivity of Nonmetallic Solids with Isotopic Impurities
Authors: Gairola R. P. 
Published: July 2007

AbstractUsing thermodynamic Green's function technique, it is shown that the inclusion of anharmonic terms along with the mass and force constant change terms arising due to isotopic impurities in the crystal Hamiltonian, leads to a cross term ΓAD of defect with anharmonic parameters in the expression for the phonon width. This interaction term ΓAD, which varies as DΩ3T, contributes significantly in the vicinity of thermal conductivity maximum, thereby giving a good agreement between theory and experiment, as seen in the analysis for germanium and magnesium stannide solids. A plausible estimate is given for the interaction parameter D taking a linear chain model as example. Due to the occurrence of this interaction term ΓAD, Mathiessen's inverse summation rule no longer remains valid. The present analysis differs from those using Callaway's phenomenological model or extensions thereof, in the sense that it does not explicitly assume the validity of the inverse summation rule in the conductivity calculations, as done by earlier workers.
Pressure Effect on Phonon Frequencies and Elastic Stiffness Constants of Al
Authors: Soma T. , Itoh T. , Kagaya H.‐Matsuo 
Published: July 2007

AbstractThe lattice dynamics of Al under pressure is investigated using the local Heine‐Abarenkov model potential with volume‐dependent parameters in the perturbational method. Then, using the homogeoneous deformation method, the bulk modulus and the shear elastic constants under compression are studied theoretically, and the mode Grüneisen parameters and the pressure‐derivatives of the elastic constants for Al are obtained.
Effect of Cold Work on Hydrogenation of Nickel as Seen in the Thermoelectric Behaviour
Authors: Gupta A. C. , Nigam A. N. 
Published: July 2007

AbstractWires of nickel annealed at different temperatures are subjected to cathodic hydrogen diffusion with and without previous cold work. The d‐band shape computed for differently annealed wires are different without cold work, but almost the same after cold work. Thus the cold work distorts the d‐band in differently annealed samples to the same extent.
Coulomb Interaction and Excitons in a Superlattice
Authors: Guseinov R. R. 
Published: July 2007

AbstractAn exact expression is found for the potential of a point charge in a periodic layered system, consisting of alternating layers with two different values of the dielectric constant. The most interesting limiting cases for this potential are considered. Energy spectrum, bound energy, and the ground state radius of the exciton, which is formed by an electron and a hole, belonging to the same layer of the superlattice, are found.
Quantum Corrections to the Screening Length and Anisotropy in Magnetic Field
Authors: Fortini A. 
Published: July 2007

AbstractThe self‐consistent linearized Poisson equation leading to the screened potential of an ionized centre embedded in a free carrier plasma, is rewritten in a closed form taking into account the quantum character of the plasma. Complete resolution in the case of Boltzmann statistics clearly shows how quantum corrections cause a departure of the screening length from its usual semiclassical value. Quantum corrections are also responsible for the anisotropy of the screening in a static magnetic field. Calculations are worked out for the case of a strong quantizing field.
Ultrasonic Attenuation in Liquid Metals
Authors: Vaid B. A. , Sharma K. C. 
Published: July 2007

AbstractExcess ultrasonic attenuation in general liquid metals, including those contracting on melting, is investigated in the framework of the two‐state model, the thermodynamic theory of relaxation processes, and the recent disorder model of melting proposed by the authors for both types of melts, i.e. those contracting on melting and the others shrinking on freezing. The generalization is affected through a parameter which is solely dependent on the structural consideration, viz. the packing fraction of solid and liquid phase. The agreement of calculated values of bulk viscosity with the experimental data is encouraging.
Electronic Structure and Properties of Cubic Boron Nitride
Authors: Prasad C. , Dubey J. D. 
Published: July 2007

AbstractThe electronic structure of cubic boron nitride without and with fractional ionicity is calculated by the application of the composite wave variational version of the APW method. The main calculations are performed at the high symmetry points Γ, X, and L, and the rest of the band structure is obtained by the tight‐binding interpolation scheme of Slater and Koster. The density of states, imaginary part of the dielectric constant, and the effect of pressure on them are calculated and compared with available experimental and theoretical data.
Refraction Index Variation in the Exciton Resonance of CdS and TlInS2 Single Crystals under Laser Excitation
Authors: Lisitsa M. P. , Stolyarenko A. V. , Terekhova S. F. , Onishchenko N. A. 
Published: July 2007

AbstractThe influence of laser excitation on refraction index variation is investigated for CdS and TlInS2 single crystals at helium temperature. The values of the n variation are obtained in the region of the B‐exciton band for CdS single crystals. Bleaching of the exciton absorption bands is observed due to the Coulomb interaction screening by the carriers generated. The efficiency of Rozhdestvenskii's method of hooks for the analysis of optically induced refraction index variations in the nonstationary case is demonstrated.
Magnetooptical Effects and Optical Absorption of FeBO3 in the Region of 6A1g → 4T1g (4G), 4T2g (4G) Transitions
Authors: Zabluda V. N. , Malakhovskii A. V. , Edelman I. S. 
Published: July 2007

AbstractThe spectra of optical absorption, magnetic linear (MLD) and magnetic circular dichroism (MCD) in the weak ferromagnet FeBO3 are investigated for transitions 6A1g → 4T1g(4G) and 6A1g → 4T2g(4G) at temperatures in the range of 90 to 300 K. It is shown that the temperature dependence of the absorption intensity and the zero moments of MLD and MCD of exciton–magnon lines for the transition → 4T1g is described by an exponent exp (–T/T0) and the MLD of these lines reveal an anomalous temperature dependence. In the region of the transition → 4T2g, where there are no exciton–magnon lines, MLD is not observed at all. The strength of coupling of the exciton–magnon for the transition 4T1g with even vibration Eg is determined and its independence of temperature is shown.
Optical Absorption Studies of Plastically Deformed InSb
Authors: Vignaud D. , Farvacque J. L. 
Published: July 2007

AbstractOptical absorption studies of edge‐type dislocations are carried out on n‐ and p‐type, weakly doped InSb. Edge‐type dislocations are selectively introduced by means of uniaxial compression at 220 °C. The presence of dislocation induces two main changes in the optical absorption spectra: i) absorption tails just before the band edge, which are associated with the strong internal piezoelectric fields and ii) reduction of the intraband absorption, which are explained by the presence of trapping levels bound to the dislocations.
Three‐Band Model Applied to Narrow‐Gap HgCdTe
Authors: Fau C. , Dame J. F. , de Carvalho M. , Calas J. , Averous M. , Lombos B. A. 
Published: July 2007

AbstractHg1–xCdxTe, with x = 0.15 is a semimetal at low temperature (4.2 K) and becomes a narrow‐gap semiconductor at higher ones (77 K). Its transport properties are measured at different temperatures, magnetic fields, and hydrostatic pressures. Based on the measured data, an analytical three‐band model is developed to calculate the concentrations and mobilities of the resulting two types of electrons and one type of holes. The existence of the slow electrons are related to the presence of acceptor states in the conduction band, as it is already elucidated in the case of zerogap HgTe. The concordance of the calculated transport properties, based on this model, with the measured ones supports the subsistence of three types of carriers in the narrow‐gap HgCdTe.
Hopping Conductivity and Electron Localization in Heavily Doped ZnSe
Authors: Kasiyan V. A. , Nedeoglo D. D. , Simashkevich A. V. , Timchenko I. N. 
Published: July 2007

AbstractBy high‐temperature annealing of the starting high‐ohmic ZnSe crystals (ϱ ≈ 108 Ωcm) in liquid lead or tin low‐ohmic crystals are obtained with specific resistivity from 10−1 to 100 Ωcm. The shallow donor density in these crystals is Nd ≈ 5 × 1017 to 2 × 1018 cm−3. The degree of impurity compensation K ≈ 0.85 to 0.98. The peculiarities of the electric properties of the investigated crystals in the interval from 1.65 to 300 K are interpreted in the frames of a heavily‐doped strongly compensated semiconductor (HDCS) model. In the high temperature region a deep donor level is indicated with a temperature dependent activation energy. It is found that at low temperatures the conductivity exhibits the hopping character following the rule lg ≈ T−1/2. A quantitative comparison of the experimental results with the theory of hopping conductivity in HDCS is presented.
Study of Bonding Configurations in Amorphous GexSi1−x:H Alloys
Authors: Sala D. Della , Giovannella C. , Evangelisti F. 
Published: July 2007

AbstractThe structure of a‐GexSi1−x:H alloys produced at two different substrate temperatures by glowdischarge is investigated over the whole range of the gas composition. By comparing IR spectra and chemical analysis, an overall sticking rate three times larger for Ge than for Si is found, an occurrence which has important consequences on the tailoring of the optical gap Eg. The use of a quasi‐statistical model accounts for the intensity of the stretching bands of several hydrides present in the structure and permits to differentiate among hydrides differing only in the second neighbor atoms.