bluuebunny/crossref_metadata_2025_split huggingface dataset:
Features Peculiar to the Acoustic Properties of Intermetallic SmFe2 in the Spin Reorientation Region
Authors: Artma E. E. , Zinoveva G. P. , Korolyov A. V. , Gaviko V. S. 
Published: July 2007

AbstractIn polycrystalline specimens of intermetallic SmFe2 the temperature dependences are measured of the sound velocity and of the sound absorption coefficients. By contrast with earlier investigations, anomalies are detected in the acoustic properties at two spin‐reorientation temperatures rather than at one. The temperature dependences are characterized by a hysteresis. Possible causes of the observed anomalies in the acoustic properties of SmFe2 are discussed.
Phase Transition of Levitating Polarons
Authors: Pokatilov E. P. , Beril S. I. , Frenk M. A. 
Published: July 2007

AbstractThe binding energy is calculated of a polaron above the liquid‐helium film placed on the polar substrate. It is shown, that in the case of thick enough films the weakly‐coupled polaron state, which is not localized in the plane of film surface, possesses the deeper energy level as compared with the strongly‐coupled and localized polaronic state. However, for thin films the inverse order in the arrangement of levels occurs. From this fact it is concluded, that a polaronic phase transition is possible when decreasing the film thickness.
Electron Paramagnetic Resonance of a CO Radical Trapped in KBr
Authors: Moens P. D. W. , Matthys P. F. A. , Callens F. J. , Maes F. R. C. , Boesman E. R. 
Published: July 2007

AbstractA CO ion with axial symmetry around 〈111〉 is detected in the KBr lattice by means of electron paramagnetic resonance. This molecular ion occupies an anion vacancy and rotates rapidly around the OO axis, which coincides with a 〈111〉 direction. The spin densities on the carbon atomic orbitals are deduced from the analysis of the 13C hyperfine tensor. A comparison with the isoelectronic NO2 molecule in the same host lattice and location is made.
Change of Lattice Parameters in Highly Disperse Nickel Powders
Authors: Gamarnik M. Ya. 
Published: July 2007

AbstractA monotonous increase of the lattice parameters with the decrease of particle size is established by an X‐ray study for highly disperse nickel powders in the interval of sizes from 4.9 to 35 nm. The relative changes of lattice parameters are from 4.9 × 10−3 ± 5 × 10−4 up to 3 × 10−4 ± 1 × 10−4. The effect is explained by the decrease of the intracrystalline pressure in small particles stipulated by electrostatic interaction of the elements of crystal charge lattice. A calculated dependence of the lattice parameters which agrees with experimental curve is obtained in the frameworks of the model suggested by the charge lattice represented by an ion—electron lattice of positive ions and collectivized electrons with regard of the lattice of atomic neutral cores (the contribution of the latter is proved very small as found from the calculations).
Electronic Structure Calculations for YBa2Cu3O7 by the Self‐Consistent Crystalline Orbital Method
Authors: Filonov A. B. , Borisenko V. E. 
Published: July 2007

AbstractResults are given of electronic structure simulation for YBa2Cu3O7 calculated by the crystalline orbital method. The standard scheme of self‐consistency for charges and configurations is employed. Multiexponential representation for at least Cu3dO2p atomic orbitals with accounting for correct electronic configuration of the atoms entering the system are shown to be used for adequate simulation. A new modified scheme of self‐consistency for this type of materials is proposed.
Interference of Cherenkov and Parametric Radiation Mechanisms of a Fast Charged Particle
Authors: Nasonov N. N. , Safronov A. G. 
Published: July 2007

AbstractThe parametric X‐ray radiation of a fast charge in a medium with periodically changing refraction index is considered in the case of simultaneous fulfillment of the Vavilov‐Cherenkov radiation conditions. It is shown that if the characteristic frequencies of both types of radiation are close enough, a considerable change in the radiation structure (both, in the charge movement direction and in that of Bragg scattering) takes place. An oscillating dependence of the registered radiation versus the target thickness and viewing point is established.
K‐Shell XAFS Formation in Silicon Crystal
Authors: Pavlychev A. A. , Barry A. , Potapov S. S. 
Published: July 2007

AbstractX‐ray absorption fine structure (XAFS) formation in a silicon crystal is analysed on the basis of a quasiatomic description. The spectral dependence of the XAFS formation mechanism is investigated. The existence is shown of four specific spectral regions with different electron‐optical characteristics of the atomic surroundings and different “size” effect of XAFS formation. It is shown that (i) the sensitivity of XAFS to distant coordination shells is maximum in the interval 30 nm−1 < k < 60 nm−1 and (ii) the combination of single reflections from the surroundings and photoelectron refraction in the surroundings well describes the XAFS in a very large domain k > 25 nm−1.
Compton Profile of Polycrystalline Zinc and Cadmium
Authors: Perkkiö S. , Sharma B. K. , Manninen S. , Paakkari T. , Ahuja B. L. 
Published: July 2007

AbstractThe Compton profiles of polycrystalline zinc and cadmium are studied. The measurements are made using 59.537 keV γ‐rays. The renormalized free atom model (RFA) and the orthonormalized linear combination of atomic orbitals (LCAO) model are used to calculate the theoretical Compton profiles. The RFA model for the electron configurations 3d104s2 and 4d105s2 for zinc and cadmium, respectively, is found to give the best agreement with the experimental profiles.
Thermodynamics and Structure of Liquid Metals from the Soft Sphere Reference Fluid
Authors: Akinlade O. 
Published: July 2007

AbstractThe Gibbs‐Bogoliubov inequality is used to compute the thermodynamics and structural properties of alkali metals and Mg, Cd, Al, In, Tl, Pb using the soft sphere (SS) reference fluid. The results are compared with earlier calculations using the charged hard sphere (CHS) as a reference fluid. It is concluded that the SS reference fluid gives better results than the CHS for the quantities investigated and yields, in all cases, lower values for the free energy, thus indicating that the SS is a preferred system. From the structural point of view, the SS predicts better agreement with experiments for the position of maxima and minima of the structure factor, although it tends to overemphasize the peaks in all cases when compared with the CHS. It is suggested on the basis of the calculations that the SS could be used for more calculations involving fluid variational perturbation approach because of its relative simplicity and ability to produce remarkably good results for structure and thermodynamics of liquid metals when computed values are compared with experiments.
Impurity Effects on Spectral Properties of an Adatom‐Contaminated Crystal System
Authors: Lazo E. 
Published: July 2007

AbstractA Green‐function calculation is performed to investigate how the presence of impurities affects the spectral properties of the adatom and surface atoms of a semi‐infinite linear chain. The infinite set of equations is solved using the transfer matrix method, and inverting a single complex matrix that contains all information about a finite region of the chain including the adatom, the surface, and the impurity sites. The method permits to calculate the local properties on each site of the contaminated region in a very efficient form. Results of the exact calculations of the electronic densities of states are presented when a single impurity is put in many different positions and when a set of seven impurities is distributed in two different forms in the chain.
On the Electron States in a Cylindrical Quantum Box of a Wide‐Gap Semiconductor in Crossed Electric and Magnetic Fields
Authors: Das N. R. , Chakravarti A. N. 
Published: July 2007

AbstractA perturbational calculation is presented for determining the energy eigenvalues of the confined electrons in a cylindrical quantum box of a wide‐gap n‐type semiconductor in the presence of crossed electric and magnetic fields. Besides, the effects of changing the fields as well as the radius and the width of the box on the lowest quantized state in such a structure are investigated, taking n‐type GaAs as an example.
The Effect of Local Field Corrections on the Electrical Resistivity of Liquid Metals
Authors: Akinlade O. , Hussain L. A. , Matthew F. 
Published: July 2007

AbstractThe electrical resistivity of some simple liquid metals are evaluated using the charged hard‐sphere reference system for a description of the structure, while a non‐local pseudopotential is used to describe the electron‐ion interactions. It is concluded that the inclusion of local‐field corrections leads to an improvement between calculated values and experiment. Secondly it is deduced that improvements between computed results and experiments can be obtained by using a modified form of the Ziman resistivity expression which takes into account the use of a non‐local pseudopotential.
Spectral Properties of a Chain of Polyhedra
Authors: Lazo E. 
Published: July 2007

AbstractThe electronic structure of a generalized linear chain formed by polyhedra joined at their vertices is studied. Our model incorporates distinct longitudinal and transverse hoppings with respect to the chain axis, producing a variety of paths between consecutive vertex atoms in the backbone chain. The problem is formulated in terms of the Green function formalism, using a tight‐binding Hamiltonian. The infinite set of equations is solved by means of the matrix inversion method. The changes produced in the electronic structure under the topological changes in the connectivity of vertex atoms is investigated when the number of basal atoms is varied. Two continuous bands, separated by a gap are obtained, even when all hoppings are the same. As a particular case of our model the local density of states of the usual linear chain is obtained.
Study on Momentum Density of Electrons and Fermi Surface in Aluminum by Positron Annihilation
Authors: Nakashima H. , Kubota T. , Kondo H. , Murakami Y. , Tanigawa S. 
Published: July 2007

AbstractThe three‐dimensional electron–positron momentum density in aluminum is reconstructed from measurements of two‐dimensional angular correlation of positron annihilation radiations (2D‐ACAR) followed by the image reconstruction technique based on a direct Fourier transformation. On the basis of the experimental data, the Fermi surface topology, the high momentum components (HMC), the enhancement effect, and the autocorrelation function are discussed.
Two Spin–Orbit Coupling Parameter Model of the Gyromagnetic Factor for d8 Clusters in Tetragonal Symmetry
Authors: Chen Jia‐Jun , Du Mao‐Lu , Chen Kang‐Sheng 
Published: July 2007

AbstractAn analytical perturbation formula of the gyromagnetic factor for the ground state 3A2 (F) of d8 ions, in which not only the contribution from spin–orbit coupling of the central transition metal ion but also that of ligand ions is included, are obtained in tetragonal symmetry. In the derivation, the contribution of all excited states for the g‐factor is considered, and no adjustable parameter is introduced. The molecular orbital coefficients are determined by means of a semiempirical method for estimating the g‐factor. The contribution of the spin–orbit coupling of ligand ions to the g‐shift is discussed in some pseudo‐tetragonal Ni(II) compounds. The results show that the contribution must be considered, especially when the ligand ions have large spin–orbit coupling parameters. The calculation results agree well with experimental findings.
On the Scattering Rates of Free Electrons in High Purity Semiconductors at Low Lattice Temperatures
Authors: Ghorai A. K. , Bhattacharya D. P. 
Published: July 2007

AbstractAt low lattice temperatures when the phonon energy cannot be neglected in comparison to the electron energy the influence of the mass anisotropy on the scattering rates becomes pronounced. Numerical calculations are performed for Ge and Si for electron interactions with acoustic phonons.
The Odd Voigt Effect under a Strong Electric Field in Semiconductors
Authors: Shon Nguyen Hong 
Published: July 2007

AbstractThe high‐frequency conductivity tensor σik(ω) in the linear approximation of magnetic field H and in quadratic approximation of external de electric field is derived by solving the Boltzmann equation. The magneto‐optical phenomena in the Voigt configuration (when the probe electromagnetic wave propagates across the magnetic field) are investigated. It is shown that birefringence and dichroism have a component that is odd (linear) in the magnetic field and predominates over the even effect in weak magnetic field.
Transient Energy Transfer by ps‐Laser‐Induced Free‐Carrier and Photorefractive Gratings in CdTe at 1 μm
Authors: Rückmann I. , Kornack J. , Kolenda J. , Petrauskas M. , Ding Y. , Smandek B. 
Published: July 2007

AbstractThree‐beam mixing is investigated in ps‐transient grating experiments carried out on (110) CdTe at 1 μm in the case of two‐photon absorption (TPA). The coupling of three transient gratings via TPA results in an amplification of the free‐carrier transient energy transfer (TET) from pump beams to the probe beam. The competition between TET and TPA as well as the TET influence on the diffraction versus intensity curve are investigated experimentally and are studied theoretically using a model including nonlinear absorption and mixed gratings. Furthermore, for the first time the contribution of the ps‐photorefractive coupling to the probe‐beam diffraction signal is observed investigating the orientational dependence of diffraction kinetics.
LO‐Phonon Generation with Energy Collision Broadening in Polar Semiconductors
Authors: Král K. 
Published: July 2007

AbstractThe generation of LO‐phonons in the process of the hot electron cooling in polar semiconductors is studied theoretically. The generation rate formula is derived in the frame of the theory of the nonequilibrium statistical operator. The electron energy collision broadening is included in an approximation which meets the requirements of the elementary thermodynamics. Numerical results giving the generation rate and quasi‐steady state LO‐phonon distribution function in some materials are presented. The generalization of the generation rate formula to the case of the nonthermalized electronic system is also given.
The Critical Current Density and the Curvature of the Magnetic Field in Epitaxial YBaCuO Films
Authors: Glatzer D. , Forkl A. , Theuss H. , Habermeier H. U. , Kronmüller H. 
Published: July 2007

AbstractThe magnetic flux density distribution in thin epitaxial YBaCuO films is detected using the magneto‐optical Faraday effect. The external magnetic field is applied perpendicular to the film plane after zero field cooling. The results for the magnetic polarization, J, the critical current density, jc, and the magnetic field, μ0H*, of complete flux penetration are compared with SQUID magnetometer measurements. The flux density gradients as derived from the detected flux density distribution reveal the importance of the radial field in the investigated thin films with respect to the critical current density jc and the magnetic polarization J.
Correlations of the X‐Ray K‐Absorption Edge Shift (Chemical Shift) in Some Cu(II) Systems with Effective Charge and Bond Length
Authors: Pandey S. K. , Chetal A. R. 
Published: July 2007

AbstractX‐ray absorption Cu K‐edge spectra are recorded in some Cu(II) compounds. La2CuO4, CuSO4 · 5 H2O, CuCO3 · Cu(OH)2, CuWO4, (NH4)2SO4 · CuSO4 · 6 H2O, and Cu(OH)2 and also there of pure Cu metal using a Cauchois‐type bent‐crystal X‐ray spectrograph. The X‐ray absorption chemical‐shift, ΔE, in each of the above Cu(II) compounds is measured. The chemical‐shift, ΔE, is correlated separately with each of its two governing factors, the effective charge, q, and the bond length, R, in the systems under study on the basis of the least‐squares regression analysis. Also the extent is determined to which the chemical‐shift, ΔE, is explained by each of the two factors, the effective charge, q, and the bond length, R, separately. It is also shown that the chemical‐shift, ΔE, prominently depends on the effective charge, q, and the bond length, R, i.e. q and R explain almost the total variation in chemical‐shift, ΔE, in the systems under study.
Aluminium XAS and NMR Spectroscopic Studies of Calcium Aluminosilicate Glasses
Authors: Landron C. , Cote B. , Massiot D. , Coutures J. P. , Flank A. M. , Flank A. M. 
Published: July 2007

AbstractThe local geometric and electronic order around aluminium atoms in calcium aluminosilicate glasses is comparatively investigated by X‐ray absorption (XAS) and by nuclear magnetic resonance (MAS NMR). The Al absorption spectra contain features which can be decomposed into two subpeaks, the relative contribution of the subpeaks appears to be related to the silicon/aluminium ratio in the glass. MAS NMR data analysis of the same samples clearly shows differences in site structures. It is of great interest to compare the results of both techniques in order to describe a reliable picture of Al surroundings related to a number of physical properties of calcium aluminosilicate glasses.
Electronic and Optical Properties of PtSn2
Authors: Gupta A. , Gupta R. Sen 
Published: July 2007

AbstractThe electronic energy bands of PtSn2 are calculated using composite wave variational version of the APW method. The results show a narrowing of d‐band which indicates a weaker d‐d overlap interaction between Pt atoms. A comparative study of this band structure result with that of PtAl2 and Pt provide interesting information about d‐d interaction as a function of primary interatomic distance. From the band structure results, density of states, joint density of states, ε2(ω) spectra and the Fermi surfaces are calculated and interpreted.
A Correlation Study of Large Potassium Neutral Clusters
Authors: Kanal K. M. , Ray A. K. , Howard I. A. 
Published: July 2007

AbstractAccurate ab initio molecular‐orbital calculations are performed for the neutral Kn (8 ≦ n ≦ 13) clusters. The effects of electron correlation are studied using many‐body perturbation theory. Detailed electronic structures of these clusters are studied. Stabilities from the points of view of binding and fragmentation energies are discussed and, wherever possible, results are compared with published data in the literature.
Coupled Pairs of Cu+OCN− in KCl Studied by Optical Absorption and Thermally Stimulated Depolarization Current
Authors: Oliveira L. , Magna P. , Gallo N. J. H. , Domenicucci E. C. , Li M. Siu 
Published: July 2007

AbstractCu+‐OCN− coupled pairs are observed through a systematic correlation study of different KCl + 1 at% CuCl, KCl + 1 at% KOCN, and KCl + 1 at% KOCN + 1 at% CuCl single crystals. The optical absorption measurements show that the forbidden 3d10 + 3d94s transition Cu+ is completely split when disturbed by an OCN− molecule. As a result new Cu+ absorption bands besides the 260 nm partially allowed transition are observed at 218, 228, 242, and 251 nm. These new bands are attributed to interaction with OCN−. The thermally stimulated depolarization current (TSDS) is best fitted when the OCN− perturbed Cu+ is considered to be a double relaxation type system rather than a single one. This is very well borne out for the two last single crystals samples. Also the presence of an unwanted isotopic impurity 18O1214N− is discussed in the doped samples. Furthermore through a thermal process it is shown that there is effectively a coupling between Cu+ and OCN−.
A New Class of Empirical Many‐Body Potential Energy Functions for Bulk and Cluster Properties
Authors: Erkoç Ş. 
Published: July 2007

AbstractA new empirical many‐body potential energy function (PEF) is proposed, which comprices two‐ and three‐body atomic interactions. The two‐body potential is a kind of hybrid function and the three‐body potential is formed by additive and nonadditive functions. The additive part is expressed in terms of two‐body interactions, and the nonadditive part is expressed as triple‐dipole function. The PEF satisfies bulk cohesive energy, bulk stability condition, and bulk modulus. The PEF is parameterized for gold, silver, and copper elements in f.c.c. crystal structure. The elastic constants of the elements are calculated, and the structural stability and energetics of microclusters containing 3 to 7 atoms of the same elements are investigated. The calculated elastic constants are in good agreement with experimental values, and the most stable microcluster geometries are qualitatively in agreement with the available literature data.
A Classification of the Dislocation‐Related Photoluminescencence in Silicon
Authors: Lelikov Yu. S. , Rebane Yu. T. , Ruvimov S. , Sitnikova A. A. , Tarhin D. V. , Shreter Yu. G. 
Published: July 2007

AbstractThe photoluminescence (PL) spectra of the basic extended defects in Si are obtained. A new classification of the PL lines is proposed according to the squared edge components of the Burger's vectors of the dislocations which surround the structural defects. The different manifold splitting of the various dislocation‐related PL lines are predicted for external perturbations violating the crystal symmetry. The possibility of the passivation of these dislocation cores by transition metal impurities is also discussed.
Stacking Fault Energy and Phase Stability in Long‐Range Ordered Cu–Zn–Al Alloys
Authors: Ahlers M. 
Published: July 2007

AbstractThe close‐packed martensitic phases in Cu–Zu–Al alloys can be described as an f.c.t. ordered lattice into which stacking faults are introduced. The stacking fault energy would be essentially the same as for the disordered α‐phase, but is reduced due to an additional lattice distortion which depends on the ordering energy of the f.c.t. lattice. In the 2 H martensite with a stacking fault on each second plane, the stacking faults interact, leading to a small increase in energy. Thus, in these ordered martensites the stacking fault energy depends not only on the composition, but also on the ordering energy and on the lattice distortion associated with it. These observations can be relevant to understand the dislocation mobility in other f.c.t. long‐range ordered alloys.
Internal Friction Studies on Oxygen–Oxygen Interaction in Niobium. I. Experimental Results and Application of Previous Interpretations
Authors: Weller M. , Haneczok G. , Diehl J. 
Published: July 2007

AbstractIn order to further clarify the long‐lasting controversy on the origin of the broadening of the Snoek maxima of heavy solute interstitial atoms (C. N. O.) in the internal friction of b.c.c. metals due to an interaction between those atoms measurements were carried out on niobium with various oxygen contents (0.1 to 0.85 at%) by applying frequencies of about 1 Hz and about 1 kHz to identical specimens. The means activation enthalpy of relaxation as determined from the frequency shift of the peak temperatures turns out to be independent of the oxygen content, Hm = (1.15 ± 0.01) eV. The maxima are rather symmetrically broadened and shifted to higher temperature with increasing oxygen content. They are analysed in terms of previously introduced models. The clustering model proposing a superposition of discrete Debye submaxima for O pairs, triplets, etc. does not give an adequate description of the total Snock maxima. Consequently, their broadening may only be accounted for by a continuous distribution of relaxation times. Attempts with empirical approaches, like Gaussian or Fuoss‐Kirkwood distributions, yield a better but still insufficient agreement with the measurements. This indicates that an appropriate physical model for the interaction of interstitial solute atoms in b.c.c. metals is required to match the experimental data with their precision reached now.