bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonadiabatic Electron–Phonon Interaction. Matrix Continued Fraction Treatments and Reduction of High‐Dimensional Problems
Authors: Scheuing A. , Reineker P. , Durst C. , Sigmund E. 
Published: July 2007

AbstractAn electronic two‐level system interacting with two different vibrational modes via displacive and transitive couplings is investigated. The eigensolutions are determined using a matrix continued fraction method including infinite matrices. The approximations used in the numerical evaluation are discussed. As another example for the applicability of the continued fraction method it is shown that the E–e‐Jahn‐Teller Hamiltonian proves to be a specialized case, whose eigenvalue problem may be solved using ordinary continued fractions. Finally, the eigenvalue problem of the extended Hubbard Hamiltonian of a dimer with linear local electron–phonon coupling is reduced to the evaluation of a matrix continued fraction with three‐dimensional matrices.
Quasi‐Resonance in Hydrostatically Compressed Isotopic Mixed Crystals of Deuteronaphthalene
Authors: Gaidai S. I. , Meletov K. P. , Shchanov M. F. 
Published: July 2007

AbstractSpectra of absorption and luminescence of two isotopic mixed crystals (IMC) of deuteronaphthalene for the 0.1% C10H8 guest in C10D8 host and for the 0.1% C10H8 guest in C10H2D6 host are measured in the range of the lowest singlet exciton transition at T = 4.2 under hydrostatic pressure up to 2 GPa. The dependence of the binding energy E and of the localization amplitude |a0|2 of the exciton on the impurity is determined in a wide range of values, involving the cross region. The dependences are verified quantitatively by the Rashba theory of quasiresonance.
Effect of Orbit–Lattice Interaction on Mössbauer Quadrupole Splitting of Iron(II) in Fe(p‐CH3C6H4SO3)2
Authors: Sinha T. P. , Choudhary S. N. , Srivastava K. K. P. 
Published: July 2007

AbstractThe effect of vibronic coupling between low lying electronic states on the temperature dependence of the Mössbauer quadrupole splitting of Fe(II) in Fe(p‐CH3C6H4SO3)2 is theoretically analysed over 9 to 291 K. This results in a better agreement between theoretical and experimental data than hitherto obtained from the static crystal field scheme. It shows that the orbit–lattice interaction is important for ferrous ions and its effect should be duely included in the interpretation of Mössbauer observables as a function of temperature.
Two‐Particle Monte‐Carlo Method for Warm Electrons in a High‐Frequency Electric Field
Authors: Kancleris Ž. , Matulis A. 
Published: July 2007

AbstractA two‐particle Monte‐Carlo method for the numerical simulation of the nonhomogeneous kinetic equations useful for the treatment of warm electron properties in the case of ac fields is given. The method is based on the solution of the Green function equation by the Monte‐Carlo technique. The electric field time dependence is taken into account by the simulation of the motion of particles with variable weights. Making use of the proposed method the frequency dependence of the non‐linearity coefficient for p‐Ge is calculated.
Random Motion Studied by Time Delayed Mössbauer Spectroscopy
Authors: Vapirev E. I. , Bourin K. I. , Christoskov I. D. , Tsankov L. T. , Kamenov P. S. 
Published: July 2007

AbstractThe time dependence of resonantly filtered radiation is studied in the case of source or absorber nuclei moving randomly. Experiments are performed for liquid absorber and the results are compared with theory.
4f Optical Absorption Model in Rare‐Earth Semiconducting Compounds
Authors: Parlebas J. C. , Chetouane K. , Hugel J. 
Published: July 2007

AbstractThe effect is explored of a local attractive 4f hole potential Ufd on the contribution to the optical absorption from electronic 4f → 5d transitions in SmS‐type compounds. After formulating the problem of the imaginary part of the dielectric function in a general manner, a simple numerical study of a two band model is presented to illustrate the essential Ufd effect and to make some qualitative contact with available data on the metallic and semiconducting phases of SmS.
First Principles Prediction of Static Structural Properties of Aluminum from Pressures and Total Energies
Authors: Rodríguez C. O. , Cappannini O. M. , y Blancá E. L. Peltzer , Casali R. A. 
Published: July 2007

AbstractGround state structural properties (equilibrium lattice constant, bulk modulus and its pressure derivative) of aluminum are obtained using an ab‐initio selfconsistent calculation of pressures and total energies. First principles non‐local pseudopotentials and Wigner's interpolation formula for exchange and correlation are used within the local density functional formalism. Values obtained are in good agreement (errors less than 6%) with experimental ones. These results are obtained for the first time for Al from a direct first principles pseudopotential calculation of pressure–volume relation. A comparison is made with results from alternative schemes.
X‐Ray Induced Relaxation Band Due to Higher Aggregates in KCl:Pb
Authors: Mukherjee M. L. , Capelletti R. 
Published: July 2007

AbstractAlthough aggregation of impurity centres in doped alkali halides upon X‐irradiation is proposed earlier, direct evidence of such centres having dipole moment is reported here for the first time by the method of ionic thermocurrents (ITC). The norma Idipolar relaxation band in KCl: Pb is located around 224 K, while sometimes a small band at about 160 K is found in the ITC spectrum of heavily doped systems. Exposure to X‐rays increases this band around 160 K at the cost of the 224 K dipolar band. Optical absorption in the A‐band of KCl:Pb, along with ITC measurements indicates that higher aggregates of I–V dipoles are easily formed in heavily doped systems. Formation and growth of the 160 K ITC band upon X‐ray irradiation are explained from the fact that the effect of X‐irradiation is to increase the rate of aggregation of I–V dipoles, through temporary electron trapping by lead ions.
EPR and Optical Absorption of Cr3+ in CsCl and CsBr
Authors: Elbers G. , Remme S. , Lehmann G. 
Published: July 2007

AbstractEPR spectra of Cr3+ in CsCl and CsBr single crystals grown from aqueous solutions are studied at 293 and 20 K. In both cases two tetragonal centers with zero‐field splittings in ratios near 2:1 and several centers of orthorhombic and monoclinic site symmetries, respectively, are found. Their relative concentrations vary with growth conditions in CsCl. The structures of these centers can be understood assuming incorporation on interstitial sites similar to those for divalent transition‐metal ions. Application of the superposition model suggests coordination by mixed ligands, the tetragonal centers most likely are [CrX4/2H2OY] complexes with X = Cl or Br and Y = H2O or OH− and Cl− or Br−, respectively. Analysis of the optical absorption spectra also supports these models.
Lattice Dynamics of Al and Pb
Authors: Thakur V. K. , Singh T. N. 
Published: July 2007

AbstractThe experimentally observed dispersion curve, specific heat, and Debye characteristic temperatures of the complex polyvalent aluminium and lead are reproduced using the phenomenological model developed earlier for the study of lattice dynamics of f.c.c. noble and transition metals. The model is employed to calculate the compressibilities of Al and Pb. The agreement between calculated and experimental results is satisfactory.
On the Dynamical Scaling Behaviour in Nucleation and Growth Kinetics
Authors: Lorenz B. 
Published: July 2007

AbstractA one‐dimensional model for nucleation and growth is investigated with respect to the validity of scaling relations for spatial correlation functions. On the basis of the rigorous solution for the grain‐size and cluster‐size distribution functions the corresponding autocorrelation functions for grains and clusters are calculated. Scaling relations are detected only in the late time behaviour of the cluster autocorrelation function.
On the Luminescence at the Surface and in the Surface Space Charge Region
Authors: Vakulenko A. V. , Vardanyan R. A. , Hovakimyan L. B. 
Published: July 2007

AbstractThe radiative transitions of excess electrons to the levels, associated with the semiconductor surface states and deep impurity states in the surface space charge region are investigated. Expressions for the corresponding cross‐sections of the spontaneous light emission are obtained. It is shown, that the luminescence spectral lines, corresponding to the surface and impurity states, can be identified by their polarization dependences.
Electronic Structure of Disordered Alloys. Effect of Off‐Diagonal Disorder
Authors: Dahmani L. , Brezini A. , Sebbani M. , Deppolier C. 
Published: July 2007

AbstractA method is presented for calculating the density of electronic states on a Bethe lattice. A random binary alloy A1−cBc is considered. Extensive results are presented and compared with other theories. In particular off‐diagonal disorder is taken into account.
Binding Energy of Excitons in a Polar Crystal Slab
Authors: Gu Shi‐Wei , Shen Meng‐Yan 
Published: July 2007

AbstractBased on previous results, we calculate the ground state energy, the first excited state energy, and the binding energy of an exciton in a polar crystal slab. We find that the polaron effect increases the binding energy of the slab exciton, but decreases the energy difference between the first excited state energy and the ground state energy.
Mobility Edges for Interacting Electrons Based on Hubbard's Alloy Analogy
Authors: Kolley E. , Kolley W. 
Published: July 2007

AbstractWith respect to localization the interacting electron system in disordered alloys AcB1−c is studied within the random Hubbard model by means of the alloy analogy approximation. The dc conductivity affected by localization is calculated, at T = 0 and d = 3, in the framework of a four (two genuine, two fictitious)‐component CPA (coherent potential approximation). Extensive numerical results are presented for an open mobility‐edge trajectory, conductivities, and a phase diagram on the disorder‐interaction plane, typifying the discrete probability distribution. Significant differences to results of other approaches based upon continuous, rectangular or Gaussian randomness are pointed out.
Spin–Orbit and Crystal‐Field Matrices of d4,6 Configuration and Application to RbFeCl3
Authors: Wei‐Li Shuen , Min‐Guang Zhao 
Published: July 2007

AbstractThe spin–orbit and crystal‐field matrices of d4,6 configuration with C3v symmetry are derived based on the weak‐field scheme. Utilizing these matrices obtained and the approximate SCF d‐orbit of Fe2+ proposed by Zhao, the zero‐field splitting, optical absorption bands, and the Zeeman dependences are calculated for RbFeCl3. The calculation results agree well with experimental findings.
The Temperature Dependence of the Resistivity of Liquid Copper
Authors: Chaïb C. , Gasser J. G. 
Published: July 2007

AbstractThe high melting point of copper (1083 °C) explains why the resistivity of the pure liquid is not well known. Important differences exist between the scarce old data. In this paper new accurate measurements are presented and the temperature dependence of the resistivity is discussed in the framework of Ziman's formalism in terms of structure factor and form factor. Both, experimental (obtained by neutron scattering experiments) and calculated (following a hard sphere description) structure factors are used. The form factor is deduced from model pseudo‐potentials which take into account the d band like the Moriarty (1972) potential or from the t matrix expressed in terms of phase shifts. The different calculations lead to a fairly good agreement.
Magnetovolume Effects in MnAs. Role of Space Spin Correlations
Authors: Gribanov I. F. , Zavadskii E. A. 
Published: July 2007

AbstractThe results of experimental separation of the various contributions to the MnAs volume magnetostriction in a wide range of temperatures are presented. This separation is made by determination of different magnetovolume constants from forced volume magnetostriction and susceptibility measurements using a phenomenological theory, in which both itinerant electron and local moment characters are taken into account. It is shown that the main contribution to the spontaneous magnetovolume effect in the ferromagnetic region and to the discontinuous volume change at the Curie temperature is the exchange striction. The band contribution connected with the change of the local moment magnitude in these cases is small. It is obtained that there are strong spin‐spin correlations near and above the Curie point, so the molecular field approximation often used for the description of the MnAs magnetic behavior is inadequate in this temperature region. The results obtained are used to estimate the temperature variation of the local magnetic moment magnitude in MnAs.
Magnetic Field‐Induced Transitions in the Mo4 Cluster Compounds GaMo4S8 and GaMo4Se8 Showing Heavy Fermion Behaviour
Authors: Rastogi A. K. , Wohlfarth E. P. 
Published: July 2007

AbstractThe magnetization versus field curves of GaMo4X8 (X = S, Se) show magnetic field induced transitions at 5 and 1 kOe at 4.2 K, respectively. The critical fields at different temperatures are obtained from differential susceptibility measurements. Field cooled specimens are also investigated. A provisional magnetic phase diagram is constructred. The transition is ascribed to crystal anisotropy effects.
Aggregation Kinetics of Divalent Impurity–Vacancy Dipoles in Alkali‐Halide Matrix. I. Theoretical Approach
Authors: Poźzniak J. , Berg G. , Galbatar T. 
Published: July 2007

AbstractApproximate solutions of the equations describing the kinetics of reversible agregation reactions of the divalent‐impurity–vacancy dipoles in alkali halide crystals are obtained in which the dimers and trimers are assumed to be the only aggregation products. Using the solutions obtained a method is elaborated permitting to calculate the rate constants of individual reactions on the basis of the knowledge of the time evolution of the dipole concentration.
Pressure Effect on the Melting Point of Noble Metals
Authors: Soma T. , Suzuki S. , Kagaya H.‐Matsuo 
Published: July 2007

AbstractThe temperature dependence of the mean‐square displacement for noble metals is quantitatively calculated by using the treatment for the lattice dynamics by Kulshreshta et al. The Debye temperature at higher and lower temperatures is also estimated using Debye's model. Then, using the volume dependence of the mean‐square displacement the pressure effect on the melting point of Ag and Au is studied by Lindeman's melting law, and the melting curve obtained increases as function of the compressed volume.
Recursion Method for the Density of States of Bond‐Diluted Central‐Force Elastic Triangular Lattices
Authors: Böttger H. , Freyberg A. , Wegener D. 
Published: July 2007

AbstractThe vibrational density of states of two‐dimensional bond‐diluted triangular lattices with nearest‐neighbour central forces is calculated with the aid of the recursion method by means of termination of the continued fraction by a constant parameter and by embedding the system into an effective medium. Unlike the effective‐medium theory, the recursion method provides a rather peaky structure of the density of states, especially for systems near the rigidity threshold.
On Field Emission from Ultrathin Films of Semiconductors with Effects of Image Forces
Authors: Bose M. K. , Majumdar C. , Maity A. B. , Chakravarti A. N. 
Published: July 2007

AbstractAn attempt is made to investigate the effects of size quantization on field emission from ultrathin films of degenerate wide‐gap semiconductors, taking the image force into consideration. It is noted, taking n‐type GaAs as an example, that size quantization enhances the field emission by several orders of magnitude as compared to that of bulk specimens. Such quantization also leads to oscillatory behavior of the emission with changing film thickness and to a significant dependence of the emission on field strength and carrier concentration.
An Improved Virtual Mode Theory of ATR Experiments on Surface Polaritons. Application to Long‐Range Surface Plasmon‐Polaritons in Asymmetric Layer Structures
Authors: Wendler L. , Haupt R. 
Published: July 2007

AbstractThe damping properties of surface polaritons, especially long‐range surface plasmon‐polaritons (LRSP) in asymmetric layer structures are analyzed taking into account the presence of a coupling prism. Both, the response treatment to calculate attenuated‐total‐reflection (ATR) spectra and the virtual mode treatment are used. Two different types of virtual modes are analyzed. One of them describes the propagation properties of the surface polariton in the presence of both intrinsic and radiative damping. The other type describes a surface polariton with a driving field and hence this mode allows to find out the optimum conditions for the ATR experiment. These two modes are investigated in detail and the results of the numerical calculation are presented in graphical form. The results for the ATR configuration show that in asymmetric embedded silver layers the propagation length exceeds the value for the symmetric embedded one significantly.
Calculated Electronic Structures and Chemical Bonding in Sc and Y Carbides
Authors: Zhukov V. P. , Gubanov V. A. , Jepsen O. , Christensen N. E. , Andersen O. K. 
Published: July 2007

AbstractThe energy band structures of ScCx and YCx for x = 1.0, 0.75, and 0.5 are calculated self‐consistently by the LMTO method. From the total energies, the theoretical values of the lattice constants and the energies of vacancy formation are determined. It is shown that in YCx for x > 0.7 the metalloid vacancies are stabilized energetically and it is suggested that vacancies in YCx for x < 0.7 and in ScCx for all x are formed when the compounds are synthesized at high temperature and they persist at low temperatures as a result of quenching. Furthermore the changes in the energy band structures are studied and cohesive properties of these compounds when carbon is substituted by oxygen or nitrogen.
Effects of Spin Fluctuations on the Magnetism of (Fe1−xCox)Si
Authors: Inoue J. , Hattori T. , Shimizu M. 
Published: July 2007

AbstractCurie temperature and temperature dependence of the spin susceptibility for (Fe1−xCox)Si are calculated by taking into account the effect of spin fluctuations in the Gaussian approximation. Saturation magnetization and the low‐temperature specific heat coefficients are calculated making use of the rigid band approximation. Qualitative agreement between the theoretical and experimental results is obtained.
The Role of Gadolinium in the Magnetocrystalline Anisotropy of (Y1−xGdx)2Co17 Pseudobinaries
Authors: Kąkol Z. , Figiel H. , Apusta Cz. 
Published: July 2007

AbstractMagnetic measurements of (Y1−xGdx)2Co17 oriented powder samples versus temperature in the 78 to 300 K range are made, and the K1 and K2 values are calculated. To explain the differences of the anisotropy energy of Y2Co17 and Gd2Co17 compounds, the dipolar interactions of Gd moments are analysed. The values of the anisotropy energy calculated from dipolar interactions are in very good agreement with experimental values.
Lattice Parameters, Energy Gaps, and Magnetic Properties of the CdxHgyMnzTe Alloy System
Authors: Manhas S. , Khulbe K. C. , Beckett D. J. S. , Lamarche G. , Woolley J. C. 
Published: July 2007

AbstractPolycrystalline samples of CdxHgyMnzTe alloys (x + y + z = 1) are prepared by the standard melt and anneal technique. Debye‐Scherrer powder X‐ray photographs are used to determine equilibrium conditions in the alloys, to delineate the range of single phase solid solution and to determine values of zinc blende lattice parameter a. It is found that in the zinc blende field the variation of a with composition can be written as a = (0.6481 – 0.0019y – 0.0144z) nm. Optical absorption measurements are made to give room temperature values of energy gap Eg for the single phase alloys and it is found that to a good approximation the composition variation of Eg is given by Eg = (1.46 – 1.62y + 1.33z) eV. Measurements of magnetic susceptibility in the temperature range 4 to 250 K are made to give values of Tg, the spin‐glass transition temperature, and θ, the Curie‐Weiss temperature. Analysis of these data shows that for samples with Eg > 1.5 eV, the results are well explained by the superexchange mechanism previously used in the analysis of the CdxHgyMnzTe etc. results, but that for the cases with Eg ≦ 1.5 eV a Bloembergen‐Rowland type of interaction needs to be included in order to explain the experimental values of Tg and θ.
Correlation between the 1.1 and 1.45 eV Emission Bands and the F+ Optical Absorption Bands in ZnS Crystals
Authors: Matsuura K. , Kishida S. , Fukata Y. , Tsurumi I. 
Published: July 2007

AbstractZinc sulfide crystals are fired successively in a Zn liquid at 1184 °C and annealed isochronally. The emission spectra between 700 and 1200 nm and the optical absorption bands ascribed to F+ centres are measured in the specimens. The Zn treatments introduce emission bands with peaks at 1.1 and 1.45 eV, which are reported by other workers. These bands are annealed in company with F+ centers. Therefore it is proposed that these emission bands are due to F+ centers.
Polariton Theory of Infrared Absorption Edges in SiO2, GeO2, and GeO2‐Doped SiO2 Glasses
Authors: Sun Hong , Fang Junxin 
Published: July 2007

AbstractThe infrared absorption edges of SiO2 and GeO2 glasses are calculated using a polariton theory. The glasses are modeled by sets of non‐interacting anharmonic oscillators with vibration frequencies equal to those of the asymmetric stretching motions of T–O–T (T  Si, Ge) bonds. The structural disorders of the glasses are considered by introducing distributions of the vibration freéuencies. The polariton effect as well as the contributions from other vibration modes in the glasses to the infrared absorption edges are studied. Furthermore, by a “mixed crystal” model, mixed up by three different oscillators corresponding to the asymmetric stretching motions of SiOSi, GeOGe, and SiOGe bonds, respectively, the infrared absorption edges in GeO2‐doped SiO2 glasses are calculated using the virtual crystal and superposition approximations to examine which one is closer to the experiments.
Alternative Quasi‐Classical Transport Equations. II. Boltzmann's Equation and the Electron Distribution Function for MIS Systems
Authors: Schnittler Ch. , Scherf S. 
Published: July 2007

AbstractIn Part I of this paper a new quasi‐classical formulation of transport equations in the framework of the local‐density approximation is reported including wave function effects due to the potential barrier near an interface. For practical applications to semiconductor devices the non‐equilibrium distribution function of the charge carriers is to be determined. In Part II this problem will be solved for a MIS field effect transistor as a typical example. For this system Boltzmann's equation is formulated and solved in a more general manner than before. The scattering processes in the bulk are considered together with partly diffuse interface scattering which is introduced by means of special boundary conditions. The transport properties of the MIS field effect transistor will be calculated later in Part III of this paper.