bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamical Correlations in Liquid Sodium
Authors: Jain K. C. , Gupta N. , Pratap A. , Saxena N. S. 
Published: July 2007

AbstractThe theory developed by Glass and Rice is used to study the atomic motions in liquid sodium in terms of the velocity autocorrelation function, power spectrum, and mean square displacement at 373 K. The interatomic pair potential for liquid sodium at the melting temperature is obtained by using Ashcroft's pseudopotential theory with the dielectric function of Vashishta and Singwi. Results of these calculations are compared with the results obtained by Miranda and Tora from molecular dynamics at 373 K. These results of dynamical variables obtained by the theory of Glass and Rice show a good agreement with the molecular dynamics results for liquid sodium. Besides, calculations are also done for the coherent behaviour of liquid sodium in terms of the dynamical structure factor S(k, ω). Quasi dispersion curves derived from the peak positions of the longitudinal current‐current correlation function ω2S(k, ω)/ω−2 against k, are in good agreement with experimental phonon dispersion results of Cocking for liquid sodium.
Fermi Surface Charactertics of Palladium
Authors: Ahuja R. , Solanki A. K. , Auluck S. 
Published: July 2007

AbstractThe Fermi surface of palladium is calculated using the linear muffin tin orbitalmethod in the atomic sphere approximation. The calculations demonstrate the need to include relativistic corrections for a good representation of the Fermi surface. Calculations are performed including the f‐band potential parameters and by increasing the number of k points in the Brillouin zone summation. With the view to ascertain which exchange‐correlation potential is appropriate for Fermi surface work calculations are made using a number of exchange‐correlation potentials. The calculations indicate that the Slater Xα exchange with α = 0.75 provides the best agreement with the experimental Fermi surface data. Using this exchange the electron velocities and mass enhancement factor are calculated for the various sheets of the Fermi surface. The results are compared with the experimental data and with available theoretical calculations.
Self‐Consistent Theory of Delocalization
Authors: Olemskoi A. I. 
Published: July 2007

AbstractThe Anderson delocalization theory is constructed by analogy with the microscopic theory of superconductivity, where the square‐rooted ratio of the number of the bound sites to the total number of the impurity sites plays the role of an order parameter and the shift from the band center plays the role of a conjugate field. The spectrum dependence of the effective interaction parameter is shown to lead to anomalous behaviour of a system (2 + δ transition, where δ = 0 is the addition due to a logarithmic factor).
Configuration Interaction and Crystal Field Splitting of the Cu2+ Ion in D2d and D3h Symmetry
Authors: Gomathy V. , Basu C. , Ghosh U. S. 
Published: July 2007

AbstractThe effect of interaction of excited electronic configurations 3d84s, 3d84d, and 3d84f with the ground 3d9 configuration on the crystal field splittings of the Cu2+ ion in Cs2CuCl4 having D2d symmetry and in [Cu(NH3)2]Ag(SCN)3 having D3h symmetry is investigated. The amount by which the crystal field splittings of the Cu2+ ion in these two systems are affected by the various mechanisms of configuration interaction are estimated within the framework of crystal field theory using Richardson's wave functions for the radial integrals.
Regular Algorithm for the Solution of the Inverse Problem in Mössbauer Spectroscopy
Authors: Voronina E. V. , Ershov N. V. , Ageev A. L. , Babanov Yu. A. 
Published: July 2007

AbstractGeneralizing the regular solution algorithm the inverse problem of Mössbauer spectroscopy is proposed for obtaining the distribution function of the hyperfine interaction parameters from the spectrum. By model calculations it is shown that the algorithm is stable with respect to statistical noise and errors in the spectrum parameters. It is noticed that the algorithm is applicable strictly only to objects which properties can be described by a continuous distribution of one of the hyperfine interaction parameters. The condition of the normalization is introduced as an additional criterion of the correctness of the solution. There is a possibility of investigating the spectra with paramagnetic components. The algorithm may be applied to an analysis of both, poorly resolved and well resolved spectra.
Magnetic Properties of Pd3Fe
Authors: Maksimović G. D. , Popović Z. S. , Vukajlović F. R. , Vuletić K. 
Published: July 2007

AbstractThe Stoner model of ferromagnetism in combination with self‐consistent linear muffin‐tin paramagnetic calculations are used for the investigation of magnetic properties of the Pd3Fe compound. Very good agreement is obtained with previous more complicated spin‐polarized calculations and experiments.
Qualitative and Quantitative Differentiation of Paramagnetic Anion‐Antisite‐Related Spectra in GaAs
Authors: Goltzené A. , Schwab C. 
Published: July 2007

AbstractThe electron paramagnetic resonance spectra related to the anion antisite in GaAs may be sorted out into two groups according to their behaviour under photoexcitation and microwave saturation. This qualitative separation is quantitatively supported by different values for the central hyperfine constant and for the component linewidth of the quadruplet spectrum usually modeled by an isolated As defect. These observations lead to reinvestigate the initial extrapolation, based on the isolated PGa centre in GaP, which results in the identification of the former quadruplet. It supports the existence of several antisite‐related defects likely differing by their first shell as in GaP.
On a Simplified Analysis of the Magnetic Susceptibilities of Electrons in Ultrathin Films of Non‐Parabolic Semiconductors in the Presence of a Quantizing Magnetic Field
Authors: Ghatak K. P. , Mondal M. 
Published: July 2007

AbstractAn attempt is made to formulate simplified expressions of the dia‐and paramagnetic susceptibilities of electrons in ultrathin films of non‐parabolic semiconductors under strong magnetic quantization, taking n‐CdGeAs2 as an example. It is found, on the basis of a newly derived magneto‐dispersion relations of ultrathin films, that both the susceptibilities oscillate with increasing film thickness and increase with increasing electron concentration in the quantum limit. In addition the corresponding results for the three‐band Kane model, two‐band Kane model, and parabolic energy bands are derived as special cases of our generalized expressions.
The Dielectric Function and Reflectivity in KDP‐Type Ferroelectrics
Authors: Wesselinowa J. M. 
Published: July 2007

AbstractA Green function technique is developed to study the real and imaginary parts of the dielectric function ε(k, E) for KDP‐type ferroelectrics below and above Tc. The dependence of the numerically calculated ε(k, E) on energy E and temperature T is discussed. Using the Kramers‐Kronig analysis the refractive index n, the absorption index χ and reflectivity R are obtained for T = 120 and 300 K and are found to be in very good agreement with the experimental data for KDP.
Stable States and Ordering in Chalcogenide Vitreous Semiconductors
Authors: Maslyuk V. T. 
Published: July 2007

AbstractA chemical‐structural scheme of the stable state construction in amorphous semiconductors is proposed. Proceeding from the thermodynamic considerations the stable states, energy level diagram, and the temperature features of their population are determined. The feasability of a given approach for the description of induced structural transformations in chalcogenide vitreous glasses (ChVG) is illustrated by Müller's additivity principle.
Study of Lithium Interaction with Lattice Defects in Silicon
Authors: Myakenkaya G. S. , Gutsev G. L. , Afanaseva N. P. , Evseev V. A. , Konopleva R. F. 
Published: July 2007

AbstractA theoretical and experimental study is carried out on the behaviour of the Li donor impurity in the Si lattice with vacancy‐like (V) radiation‐induced defects. The electronic and geometrical structure of the cluster Si4H12 + Li4 simulating the V + Li4 complex in Si is calculated by the discrete variational Xα‐method. It is found that the cubic tetrahedral configuration of the complex is geometrically stable where the 8t2 state near the edge of the valence band is completely populated. The principal possibility of passivation of the V‐type defects by Li atoms is checked experimentally on n‐ and p‐Si samples with a Li concentration of ≈ 1017 cm−3 irradiated by reactor neutrons at fluences of 1.6 × 1015, 4 × 1015, and 3.4 × 1016 cm−3. The temperature dependences of the conductivity, Hall constant, and mobility are measured. It is shown that at high Li atom concentrations considerably in excess of the concentration of the dopant and radiation‐induced defects the electrical characteristics of the irradiated Si restore to the original level which is in agreement with the calculations on the passivation of the Li atoms by the V‐states in Si.
Charge Asymmetry in the Dependence of Stopping on Impact Parameter
Authors: Balashova L. L. , Kabachnik N. M. , Kondratev V. N. 
Published: July 2007

AbstractThe charge asymmetry effects in the dependence of electronic energy loss on impact parameter are studied theoretically. Allowance for some corrections to the calculations made in terms of the first‐order perturbation theory is shown to result in a dependence of stopping on projectile charge sign. Corrections for binding‐energy variations and for Coulomb deflection are allowed for in the case of stopping on inner shells of atoms. A correction for electron cloud polarization is allowed for in the case of valence electrons. Particular calculations are carried out in case of proton and antiproton stopping by Si atoms. The antiproton energy loss proves to exceed the proton energy loss in case of low values of impact parameters, and vice versa in case of high values of impact parameters. As the projectile velocity increases, all the corrections decrease, thereby resulting in that the impact parameter dependences of the proton and antiproton stoppings become in practice identical.
Activation Process Model
Authors: Tavgin V. L. , Stepanov A. V. 
Published: July 2007

AbstractAn attempt is made to produce an activation process model. The physical essence of the given model is different from that of the known activation model. The proposed model is based on following assumptions: 1) in the elementary activation interaction act the potential energy of moving atoms changes discretely or quantizes: the elementary activation act appears to be a series of quantum subsystems occurring in sequence (those subsystems may also be defined as identical harmonic oscillators); 2) an idempotent energy exchange between infrared radiation and interaction atoms causes their discrete translational motion, the process is characterized by absorption and subsequent emission of oscillation energy quantum series produced by atoms. The first principles in accordance with the model give formula, which describes the average energy of the translationally moving atoms participating in the elementary activation act. As an application of the model the formulae of solid state atomic diffusivity are derived as well as constants of first‐order chemical reaction rate. It is pointed out that the model may be applied to interpret superionic conductivity effect and atom or molecule tunnelling.
On the Kinetics of Decomposition of Dilute Al—(Zn, Mg) Alloys
Authors: Schmelzer J. 
Published: July 2007

AbstractA theoretical explanation is given of typical features of the phase separation kinetics in dilute Al—(Zn, Mg) alloys. It is shown that the experimental results can be interpreted as a decomposition in the first non‐asymptotic stage of Ostwald ripening.
Tachyons in a Crystalline Structure
Authors: Günther H. 
Published: July 2007

AbstractA class of solutions is discussed of sine‐Gordon equation applied to dislocations in solids which do not admit an interpretation in terms of particles. The energy density for these states propagates faster then the characteristic velocity of the sine‐Gordon equation. Hence they will be called tachyons. The possibility for their physical reality reflects an internal relativity of simultaneity in the crystalline solid on the basis of standards for the measurement of space and time which are inherently related to the lattice structure. Tachyons cannot be used for transmitting signals. They should, however, play a role for the quantized sine‐Gordon equation. A general symmetry relation between particle solutions and tachyon solutions of sine‐Gordon equation can be formulated with the help of a generalization of Seeger's π‐transformation.
Analysis of Far Infrared Spectra Showing Bulk and Surface Phonon‐Polaritons in CdTe Epilayers on GaAs Substrates
Authors: Dumelow T. , El Gohary A. R. , Maslin K. A. , Parker T. J. , Tilley D. R. , Ershov S. N. 
Published: July 2007

AbstractA theoretical interpretation is given of far infrared measurements by dispersive Fourier transform spectroscopy (DFTS) and attenuated total reflection (ATR) spectroscopy on two semiconductor samples, each consisting of a CdTe epitaxial layer deposited by plasma MOCVD on a GaAs substrate. In each case calculation gives a very good description of the measured spectra. The DFTS measurements reveal both the CdTe and GaAs reststrahlen bands, which lie in well‐separated spectral ranges. At frequencies above the CdTe reststrahlen band, where the CdTe layer behaves effectively as a dielectric film, interference between the beams reflected from the top and bottom of the layer leads to striking structure in the phase spectrum. ATR measurements are made in both p and s polarisation, and it is shown that a p‐polarised surface polariton is detected in the CdTe reststrahlen band, and both p‐ and s‐polarised guided waves are detected in the GaAs reststrahlen band. The frequency of the s‐polarised guided mode is found to vary with layer thickness, and both techniques provide a sensitive probe of the layer thickness.
Electronic Properties and Crystal Structure of a Methylthio Substituted Naphthalene Cation Radical Salt: (DMbTN)3(ClO4)2
Authors: Söderholm S. , Hellberg J. , Krzystek J. , Olovsson G. , Olovsson I. , von schütz J. U. 
Published: July 2007

AbstractThe crystal structure, the conductivity, and the magnetic properties of the monoclinic cation radical salt 2,7‐dimethoxy‐3,6‐bis(methylthio)naphthalene‐perchlorate [(DMbTN)3(ClO4)2] are presented. The stack of DMbTN molecules consists of triads which make the salt semiconducting, σ(300 K) ≈ 10−4 S/cm, with a band gap of 0.6 eV. In spite of the low conductivity the susceptibility is very high, about 0.27 spins/complex. This is due to the presence of significant correlation effects, causing the coupling between the spins to be antiferromagnetic with J = 56 meV. Because of the trimerization of the DMbTN stack the primary spin excitations are thermally activated triplet spin excitations of the Wannier type. The electrical and magnetic properties for T ⪅ 200 K are governed by the presence of deep defect levels in the band gap. The ESR linewidth is unusually narrow, about 1 G at 300 K, for an ion‐radical salt containing sulphur, this implies that the spin density on the sulphur atoms is very low.
The Electronic Structure of Alkaline‐Earth Oxides. IV. CaO and SrO Ground State in the Crystalline Cluster Approach
Authors: Lobatch V. A. , Rubin I. R. , Sobolev A. B. 
Published: July 2007

AbstractThe electronic structure of CaO and SrO in the ground state is calculated in terms of the crystalline cluster approach. Calculations for 27‐atom clusters at different ratios between muffin‐tin sphere radii show that in both crystals the charge configuration is similar to that obtained earlier for MgO: Mg2+ ‐O− plus one electron, distributed in the interstitial region. Such distribution of the electronic density is interpreted in terms of the theory of resonance scattering on the anion effective potential.
Examination of the Electronic Structure of Pd1−xNix Alloys by Positron Annihilation
Authors: Dęb⊙wska E. , Rudzińska‐Girulska J. 
Published: July 2007

AbstractThe entire concentration range of α‐phase Pd1−xNix alloys is studied by angular correlation of the positron annihilation radiation method at room temperature and at 90 K. The number of nearly free and d‐itinerant electrons as well as interstitial electron density against x are calculated. The increase in d‐itinerant electron number at low temperature as compared to room temperature results is possible to be the reason of the onset of ferromagnetism for the alloys with x ≦ 0.20. The electron redistribution model valid for Pd‐noble metal alloys is not confirmed for PdNi alloys. The big difference in interstitial electron densities for Pd and Ni is consistent with “common‐band” structure of PdNi alloys.
Josephson Tunneling Critical Current between Superconductors with Charge‐ or Spin‐Density Waves
Authors: Gabovich A. M. , Moiseev D. P. , Shpigel A. S. , Voitenko A. I. 
Published: July 2007

AbstractThe temperature dependences are calculated of the critical current Ic across a symmetrical tunnel Josephson junction between superconductors with partial electron spectrum dielectrization. The dielectric pairing is considered to be either singlet (charge‐density wave) or triplet (spin‐density wave). The dependences of the superconductivity gap Δ and Ic on T do not differ substantially from the well‐known Mühlschlegel and Ambegaokar‐Baratoff curves. The current Ic falls rapidly when the dielectric gap ∑ increases and the ratio ν ≡ Nnd(0)/Nd(0) decreases. Here Nnd(Nd) is the electron state density on the non‐dielectrized (dielectrized) Fermi surface section. The values jc of the critical current density for the bulk Josephson samples of ceramics BaPb1−xBixO3 with x = 0.15, 0.25, 0.3, and current—voltage characteristics of the tunnel type are measured. The quantity jc drops sharply when x increases, i.e. when the dielectrization degree increases (ν decreases).
Acoustic Second Harmonic Generation in Magnetized High Resistivity Piezoelectric Semiconductors. Effect of Nonuniform Electric Field Intensity and Carrier Concentration
Authors: Dey (Bose) M. , Ghosh S. 
Published: July 2007

AbstractThe acoustic second harmonic generation in transversely magnetised nondegenerate piezoelectric semiconductors in the presence of an electrostatic field in the direction of the wave propagation is studied theoretically. Even in trap‐free semiconductors the electrostatic field and the carrier concentration inside the sample are taken as nonuniform. It is found that the relative flux of second harmonic gets enhanced due to this nonuniformity; whereas application of magnetostatic field reduces it. Numerical estimations are made for n‐CdS at room temperature.
Study of Frustrated Ising Ferrimagnets
Authors: Li Mai Suan 
Published: July 2007

AbstractIt is shown that at low magnetic fields the paramagnetic—spin glass transition temperature Tg(H) of Ising ferrimagnets may be proportional to H2/5 for certain parameters of the model. From the calculations follows that a jump of the magnetocaloric effect at the compensation point Tk decreases with inceasing frustration. The influence of disorder on the discontinuity in the entropy at Tk is also discussed.
The Dynamics of the Domain Boundaries and Soft Lattice Mode in SbSI Crystals
Authors: Burlakov V. M. , Kiselev S. A. , Petukhov V. N. , Anikiev A. A. 
Published: July 2007

AbstractThe temperature dependence of the heat capacity of SbSI crystals in the ferroelectric phase is measured both, in the adiabatic and continuous temperature scanning regimes. The anomaly of the heat capacity in the temperature scanning regime is observed near 262 K. On the basis of the anomaly dependence on the temperature scanning rate it is concluded that this anomaly is caused by the movement activation of the domain boundaries. By the position of the anomaly maximum and its width the activation energy E0 = 0.014 (TC − T) eV/K (Tc = 298 K; Curie temperature) and the oscillation frequency of the domain wall at the pinning center μ = 3.2 × 109 Hz are determined. The manifestation of the increase of the mobility of domain boundaries in the temperature dependence of the soft ferroelectric mode is discussed.
Localization and Resonance Transmission of Light Waves in a One‐Dimensionally Disordered Dielectric. Polarization Effects
Authors: Kosobukin V. A. 
Published: July 2007

AbstractUsing a diagrammatic self‐consistent approach the problem of Anderson localization is treated for photons with different polarizations in a layered random dielectric. The diffusion coefficient and localization length are calculated for photons. Two types of anomalies are found whose manifestation is a divergency of the localization length. One of the anomalies, which originates in the total transmission of light through scatterers, is peculiar to both (s and p) polarizations. Another anomaly associated with the Brewster effect is a feature of p‐polarized waves only.
A Correlation Study of Small Potassium Cationic Clusters
Authors: Altekar S. D. , Ray A. K. 
Published: July 2007

AbstractFourth‐order many body perturbation theory is used to investigate the properties of small potassium cationic K (2 ≦ n ≦ 7) clusters. 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.
Preliminary Studies on the Stabilities of Three Types of Ordered Structures in the A(BB)O3 System
Authors: Wang Qiang , Gu Binglin , Zhang Xiaowen 
Published: July 2007

AbstractThree types of ordered domains, i.e., 1/2〈111〉, 1/2〈110〉, and 1/2〈100〉 superlattice structures, are observed, and the experimental results show that the 1/2〈111〉‐type ordered structure is much more stable than the other two. The eight‐point cluster variation method is established firstly and then the second and third neighbour interactions are taken into account. Based on the method, the phase diagrams as a function of reduced temperature (kT/J) and composition (x) are obtained and the stabilities of various ordered structures are analyzed. Theoretical results well explain the experimental observations.
Mori Approach to the Dynamics and Thermodynamics of Tunneling Centers
Authors: Junker W. , Wagner M. 
Published: July 2007

AbstractAn extended 2‐site model is considered for phonon‐assisted quantum diffusion which beyond the conventional coordinate coupling also embodies a momentum coupling initiated by the nonadiabatic behaviour of the tunneling particle. The Mori vector formalism is used to derive the fundamental Green functions, which govern both, the thermodynamics and the diffusive process. The formalism is established in such a manner that it satisfies the lowest four sum rules. Closed expressions are derived for the internal energy and the specific heat and the temporal behaviour is also discussed.
Fundamental Vibrations in Pb5(GeO4)(VO4)2 Crystals
Authors: Anachkova E. , Gospodinov M. , Nikolov A. , Svestarov P. , Petkov N. , Markov Yu. , Limonov M. , Bruchman G. 
Published: July 2007

AbstractA group‐theoretical analysis of the vibrational spectrum of lead‐germanate vanadate crystal is presented, extended with some remarks concerning positional disorder observed in the new X‐ray study of this crystal. Raman spectra of the crystal studied are compared with the theoretical results as well as with infrared and Raman spectra of similar compounds.