bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐Trapped States of Amide I Excitations in the Hydrogn‐Bonded Chain of Peptide Groups
Authors: Ichinose S. 
Published: July 2007

AbstractA theory is proposed of interactions of the Amide I excitation with lattice distortions in the hydrogen‐bonded chain of peptide groups. By studying the classical equations of motion, exact one‐soliton solutions are given in the case of the continuum limit. It is shown that the moving acoustic soliton may capture the Amide I excitation. On the other hand, the longitudinal sound velocity is slightly decreased due to the coupling between them. The nonlinearity of the hydrogn‐bond generates thus both a self‐trapping mechanism for Amide I excitations and an acoustic soliton formation for lattice vibrations.
Calculation of Bond Parameters and of Nonlinear Optical Susceptiabilities in Quartz‐Homeotypic MXO4Crystals
Authors: Engel G. F. , Defregger S. 
Published: July 2007

AbstractThe Phillips‐van Vechten (PV) dielectric theory extended to multibond compounds is used to calculate the homopolar and heteropolar energy gaps, the susceptibilities, and the ionicities of bonds in the quartz homeotypic crystals MPO4(M = Al, Ga, and Fe) and MAsO4(M = Al and Ga). Based on these results, a bond charge calculation of nonlinear optical susceptibilities is performed. Trends within the MXO4crystal class including SiO2and GeO2are discussed.
A Weakly‐Bonded Polaron in Semiconductors with a Degenerate Valence Band Edge
Authors: Gifeisman Sh. N. , Koropchanu V. P. , Pasechnik O. F. 
Published: July 2007

AbstractA polaron is considered which is bonded on a shallow acceptor near a Γ8 degenerate valence band edge. With the assumption that the polaron binding energy of the impurity centre is far smaller than the optical phonon limiting energy, an expression is obtained for the effective Hamiltonian of an impurity‐phonon system, and the ground and first excited state energy in a number of AIIBVI and AIIIBV compounds is calculated A comparison with both, the experiment and results of other papers is also made. It is shown that, if degeneration of the valence band is taken into account, the energy gap between the ground and first excited states becomes considerably lower as compared to the simple hydrogen‐like model near a non‐degenerate band.
Magneto‐Optics of Excited States of the Donor–Exciton Complex in CdS A Proof for the Excited‐Hole‐States Model
Authors: Puls J. , Henneberger F. , Gutowski J. , Hönig T. , Mikhailov G. V. 
Published: July 2007

AbstractA model for excited electronic states of exciton–impurity complexes in uniaxial II–VI semiconductors is extended to the case of an applied magnetic field. This allows to prove its validity for the donor–exciton complex (Do, X) in CdS by performing magneto‐optics of the excitation resonances of its I2 recombination line. The experiments confirm the interpretation in terms of transitions into p‐ and d‐like excited‐hole states of this complex given previously. g‐values and diamagnetic shifts are explicitly deduced and compared with the model predictions. Applications to respective complexes in other II–VI compounds are discussed.
Transport Phenomena in Mixed‐Valence Zero‐Gap Semimagnetic HgFeSe Semiconductors
Authors: Kuleev I. I. , Lyapilin I. I. , Karyagin V. V. 
Published: July 2007

AbstractOn the basis of the nondegenerate Anderson model for mixed‐valence impurities an expression is found for the electrical conductivity taking into account the radical change of the energy spectrum and damping of conduction electrons resulting from the hybridization of s and d electrons and background scattering mechanisms. It is shown that within the framework of the developed theory the anomalous change in the mobility of electrons observed in HgFeSe as a result of varying iron content can be explained without recourse to the idea of formation of the Wigner crystal from Fe3+ ions at low temperatures.
Pyroelectric Effect and Dielectric Constant in Deuterated Betaine Calcium Chloride Dihydrate
Authors: Ribeiro J. L. , Chaves M. R. , Almeida A. , Müser H. E. , Albers J. , Klöpperpieper A. 
Published: July 2007

AbstractThe dielectric constant and pyroelectric effect in deuterated betaine calcium chloride dihydrate single crystals (DBCCD) are investigated. Due to the nonexistence of typical H‐bonds in the chemical structure of this compound, deuteration does not produce the important isotopic effects observed in other betaíne compounds. The results show however that deuteration can induce local lattice strains, which, at some transition points, may give rise to structural branching processes similar to those observed in normal BCCD under hydrostatic pressure. The critical regime of the spontaneous polarization at the transition to the lowest temperature ferroelectric phase is also affected by deuteration.
Effect of Manganese Impurities on the Phase Transition Sequence in BCCD
Authors: Ribeiro J. L. , Chaves M. R. , Almeida A. , Müser H. E. , Albers J. , Klöpperpieper A. 
Published: July 2007

AbstractPyroelectric and dielectric constant measurements to study the effect of Mn impurities on the phase transition sequence of betaine calcium chloride dihydrate (BCCD) were used. Mixed crystals of B(C1‐xMnx)CD are grown from solutions with molar ratios of 5 and 20% of Mn. The chemical analysis of these crystals reveals compositions corresponding to x = 0.01 and x = 0.05, respectively. Replacing Ca by an ion with a smaller ionic radius is expected to induce local strains and local electric charges. The effect of the substitutional disorder on the different modulated commensurate phases is dicussed.
Electronic Structure of the Ideal Vacancies in (Hg, Cd)Te
Authors: Erbarut E. 
Published: July 2007

AbstractThe localized orbital method (LOM) based upon an atomic‐like basis set and empirical pseudopotential Hamiltonian in conjunction with the Green's function method is employed for the study of electron states of ideal vacancies in (Hg, Cd)Te. This method is used for the first time for a calculation of ideal vacancies in (Hg, Cd)Te. Bloch sums are formed from Gaussian orbitals of s and p symmetry on each atomic site. A systematic study shows that an accurate description of band energies and density of states can be obtained, with the use of a minimal Gaussian set. Since the relativistic terms are neglected the weighted average of the spin splitted levels of HgTe and CdTe are used for the calculation of band energies and densities of states. The calculated ideal vacancy states are in general agreement with what is known about defect levels in (Hg, Cd)Te.
Effect of Pressure on the Charge Density Wave Transitions in η‐Mo4O11 Crystal
Authors: Ôhara S. , Koyano M. , Negishi H. , Sasaki M. , Inoue M. 
Published: July 2007

AbstractElectrical resistivity ϱ versus temperature T over 4.2 to 300 K under hydrostatic pressures up to 1.2 GPa, transverse magnetoresistance, and Hall effect at 4.2 K and constant pressure are measured for a quasi‐two‐dimensional crystal of monoclinic η‐Mo4O11. Semiempirical analysis of the ϱ−T curves below the charge density wave (CDW) transition temperatures Tc1 and Tc2 shows that the temperature dependences of the CDW gap energies δ1(T) and δ2(T) follow a single universal curve, independent of applied pressures. The Shubnikov‐de Haas oscillations are also observed in these transport quantities, from which the effect of pressure on the nature of Fermi surfaces of holes and/or electrons associated with the CDW transitions is discussed qualitatively.
Magnetic Properties of Thin Films with a Gaussian Distribution of Exchange Integrals
Authors: Balcerzak T. , Mielnicki J. , Urbaniak‐Kucharczyk A. , Wiatrowski G. 
Published: July 2007

AbstractMagnetic properties of thin ferromagnetic films with Gaussian distribution of the exchange integrals are investigated in the framework of the Ising model. The correlation functions corresponding to Matsudaira's third approximation are taken into account. The numerical results for phase diagrams, magnetisation, and correlation functions are presented, and in the discussion a comparison with the results obtained for the Handrich‐Kaneyoshi distribution is made.
Thermal stability of Ti41Zr41Si18 metallic glass studied by small‐angle neutron scattering
Authors: Borély S. , Smirnov L. S. , Kovneristii Yu. K. , Nartova T. T. , Tarasova O. B. , Yu. Bezzabotnov V. , Ostanevich Yu. M. 
Published: July 2007

AbstractThe thermal stability of amorphous Ti41Zr41Si18 alloys is studied by small‐angle neutron scattering. In as‐quenched samples inhomogeneities of 8.1 nm in radius are observed which disappeared during a low temperature (250 °C) annealing treatment. The annealing carried out a 500 °C for different times (10, 30, 60 min, and 24 h) leads to a considerable increase of the scattered intensity. Because of the interparticle correlation the dimensions of the particles must be determined by the least‐squares fitting of the total scattering cross‐section formula to the measured intensity pattern. The dimensions of the particles obtained in this way do not explain the non‐monotonous time course of the scattered intensity. Therefore it is concluded that the scattering length density of the particles, that is their composition, has changed during the high temperature annealing treatment.
Charge transfer effect on formation and binding energies of vancancy pairs in NaCl and KCl
Authors: Rao B. Srinivasa , Sanyal S. P. 
Published: July 2007

AbstractCharge transfer effect on formation and binding energies of a vacancy pair in NaCl and KCl solids is investigated by using a sophisticated model potential, which includes long range many body forces. These forces have a strong influence on the relaxing ions and mechanism of polarization. The formation energy and binding energy calculated from this potential are in good agreement with experiment.
A theoretical calculation on Schottky defects in AgCl
Authors: Banhatti R. D. , Murti Y. V. G. S. , Laskar A. L. 
Published: July 2007

AbstractThe formation of Schottky defects in crystalline AgCl is investigated using interatomic potentials compatible with the macroscopic dielectric response of the solid with consistent van der Waals interaction coefficients. It is shown that two‐body central interactions in a point dipole model can yield satisfactory defect formation energy provided the dielectric polarization of the distorted defect crystal is adequately simulated. The calculated formation energy of the Schottky defect is 2.0 eV according to the potential that includes dipole—quadrupole van der Waals forces. The variation of the defect energy with temperature is studied in a quasiharmonic approximation.
Redistribution of relativistic electron flux in the region where the strong axial channeling instability occurs
Authors: Meshcherov B. R. , Tumanov V. I. 
Published: July 2007

AbstractMeasurements are made of nuclear reaction and hard bremsstrahlung yield for 50‐MeV electron motion along the silicon monocrystal axis. With the obtained data one can determine the electron flux redistribution as a function of penetration depth up to 10 μm. The scale and behaviour of this quantity allow to make a conclusion of the strong instability of particle transverse motion.
An investigation on the adhesive behaviour between transition metals titanium, niobium, tantalum, and tungsten
Authors: Li Kebin , Sun Jiansan , Liu Ling , Qi Zhenzhong 
Published: July 2007

AbstractThe contact adhesive energies between two transition metals (Nb, Ta, Ti, W) are measured in ultra‐high vacuum (UHV) condition. The results show that they depend on the cohesive energies of contacted materials. It is suggested that the adhesive interaction is caused by sharing of electrons between two metals and is mainly dependent on the densities of states of their d‐electrons. The value of the adhesive energies for two transition metals are in the range of 0.1 to 3.0 (eV/coupled atoms). When the samples are heated, the adhesive strength decreases drastically because of the segregations of nonmetallic impurities such as carbon, nitrogen, boron, and sulfur etc.
Lattice stability of gold
Authors: Singh G. 
Published: July 2007

AbstractNumerical computations of breaking strains in uniaxially stressed perfect crystals of gold are carried out using rigorous estimation of the binding energy. The total energy of the metal consists of kinetic, exchange, and correlation energies alongwith the ion‐ion and electron‐ion interactions. The numerical values of the stress and strain confirm that both the theoretical and experimental values at failure are quite close to theoretically ultimate values.
Defect surface layer effects on the Raman intensity for collective excitations of a semi‐infinite layered electron gas system
Authors: Yang J. , Lu X. J. , Horing N. J. M. 
Published: July 2007

AbstractThe transfer matrix method is applied to the determination of the Raman intensity for a semi‐infinitelayered electron gas system with a defect layer at the surface. In this, the surface layer has a different electron sheet density from that of the other layers, which is the case for realistic systems. The numerical results show that the Raman intensity at the surface plasmon energy is weakend by the presence of the defect layer under the conditions of the calculation. An analytic expression for the Raman intensity of a semi‐infinite layered electron gas having a finite number of defect layers is also presented.
The effective interparticle screening and the local‐field correction in the spin‐polarized electron system
Authors: Ivliev S. V. , Sobakin V. N. 
Published: July 2007

AbstractThe screening properties of a system of interacting spin‐polarized electrons are investigated. The exact closed equation for the vertex function is received by a many‐particle approach and the main contribution to that function is founded on the linear approximation of the generalized screened potential. The local field factor is calculated and its strong electron density dependence is demonstrated. The compressibility is positive in a wide interval of electron densities.
Soliton states in a chain with two atoms per elementary cell
Authors: Brizhik L. S. , Eremko A. A. 
Published: July 2007

AbstractThe autolocalization of carriers in a chain with two atoms per elementary cell is investigated. It is shown that in the case of big differences of neighbouring atom masses the hole in the valence band corresponds to a soliton and the electron in the conduction band is in a delocalized state, if the atom with bigger mass has the higher energetic term. In the opposite case a soliton can be formed by an electron in the conduction band. The bisoliton mechanism of superconductivity is provided by hole carriers in the first case, and electron carriers in the last one.
Investigation on the characteristics of the hubbard model
Authors: Su Gang , Ge Mo‐Lin 
Published: July 2007

AbstractIt is shown that a simple Hubbard model obeys supersymmetry of quantum mechanics under proper conditions in the attractive and the repulsive cases. The internal SO4 symmetry of that Hubbard model is found to be spontaneously broken. By unitary transformations superconductivity is investigated for a t—J model within the n‐pairing framework, and some essential results are achieved for the superconducting state.
Raman study of LiCsSO4
Authors: Lemos V. , Silveira E. S. , Melo F. E. A. , Filho J. Mendes , Pereira J. R. 
Published: July 2007

AbstractPolarized Raman spectra of single crystals of LiCsSO4 are obtained. It is found that factor group analysis isolated fails to give a consistent interpretation of the spectra. Hence, a complementary calculation, based on a group theoretical method, is employed to obtain the relative intensities for all of the internal modes. This calculation yields zero intensity for the B1g mode of the v1‐type of vibration, so that the corresponding observed band is/assumed to be the Ag symmetry mode, exclusively. Several calculated intensities result in almost negligible values for other Ag and B1g modes. This fact is particularly helpful in the analysis of experimental data thus improving assignments of the Raman bands.
Low‐Temperature Glass Properties from the Energy Spectrum
Authors: Gluzman S. 
Published: July 2007

AbstractThe low‐temperature behaviour is studied of the heat capacity of different glasses dependent on the elementary excitation spectrum characteristics. The spectrum relation to the “two‐level system” and to the “fractal” properties of glasses is discussed. “Roton” part of the spectrum is shown to play a major role in the processes determining the excessive heat capacity and the thermal conductivity.
Chemisorption on Alloys with Partial Ordering
Authors: Yang Z. X. , Lu W. C. , Zhang T. 
Published: July 2007

AbstractOne‐electron chemisorption theory and average T‐matrix approximation are used to study the chemisorption properties of binary alloys of equal concentration with long‐range order. The chemisorption energy of H atoms on Cu0.5Ni0.5 and Ni0.5Pt0.5 substrates are calculated as functions of the long‐range order. It is found that the long‐range order seems to act as the surface concentration of the alloys.
LCAO‐Calculations of the Valence Band Structure of Modified Polar Semiconductor Surfaces: Hydrogen‐, Copper‐, and Ruthenium‐Covered Gallium Arsenide (001)
Authors: Reichert B. , Jung Ch. 
Published: July 2007

AbstractResults of local density first principles LCAO calculations for a 13 layer slab of free and modified As‐terminated (1 × 1) GaAs(001) surfaces are presented. The surfaces are covered by a monolayer of hydrogen, copper, or ruthenium. The surface calculation for the hydrogen covered surface gives hydrogen‐induced and GaAs surface states in agreement with angle‐resolved photoemission results within the energy range where they are found. For the systems GaAs(001):Cu and GaAs(001): Ru metal induced gap states are predicted with a density of 2 × 1015 cm−2. The calculated surface states indicate a higher Schottky barrier for the ruthenium than for the copper covered surface.
Impurity State near the Surface of Semi‐Infinite Crystals
Authors: Shen Zhong‐Jun , Yang Bao‐Cheng , Gu Shi‐Wei 
Published: July 2007

AbstractThe ground state energy of a shallow donor impurity near a sharp surface of a semi‐infinite crystal is studied. The energy expression of the system as the function of its position is calculated using a variational method.
EPR Measurements on the Cu2+ Ion in the High‐Tc Superconductors MBa2Cu3O7 – δ
Authors: Guskos N. , Londos C. A. , Trikalinos Ch. , Paraskevas S. M. , Koufoudakis A. , Mitros C. , Gamari‐Seale H. , Niarchos D. 
Published: July 2007

AbstractEPR studies are carried out on the polycrystalline high‐Tc superconductors MBa2Cu3O7 – δ (M = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Tm, Yb and Lu). The onset of the superconducting transition is found to occur in the temperature range of 90 to 95 K (except for LaBa2Cu3O7 – δ where Tc = 50 K and PrBa2Cu3O7 – δ which is not superconducting for temperatures above 4.2 K). In all of these compounds an EPR spectrum of Cu2+ ions in the orthorhombic local symmetry, is observed. The signal intensities are found to depend strongly on the particular rare‐earth ions of the lanthanide series which are substitutionally introduced into the host lattice of YBa2Cu3O7 – δ at Y‐ions site. “Skin effect” is suggested to be the main cause of the observed changes in the intensity of EPR signals.
Recombination Radiation of a Semiconductor in the Field of a Strong Electromagnetic Wave and a Quantizing Magnetic Field
Authors: Frolov V. V. 
Published: July 2007

AbstractThe parametric transformation is considered of intense electromagnetic radiation inducing the resonance‐quantum transitions of electrons in a semiconductor between the valence band edge and the conduction band edge in the presence of a magnetic field. The dependence of the power density of the radiative recombination of a semiconductor on the frequency of radiated photons and temperature is studied. It is shown that the frequency dependence may have resonance peculiarities and the position of the resonance peculiarities depends on the intensity of the exciting electromagnetic field and the magnetic field strength.
Exciton–Polariton Dispersion of Thin Anthracene Crystals in the Thickness Range of 3 to 0.1 μm
Authors: Hashimoto S. , Ohno N. , Itoh M. 
Published: July 2007

AbstractThe effect of crystal thickness on the exciton‐polariton dispersion of anthracene is studied by using melt‐grown crystals with thicknesses ranging from 3 to 0.1 μm. The refractive indices in the vicinity of the first‐exciton resonance are determined for the polarization E ‖ b and E ‖ a by analyzing interference fringes observed in the reflection spectra at 10 K. In contrast to the results reported previously, it is found that the dispersion property is independent of the crystal thickness at least down to 0.1 μm. A comparison of the present result with the thickness‐dependent dispersion formula is presented.
Computer Modelling of the Dynamics of Space Dislocation Ensembles. I. Non‐Elastic Dislocation Approach
Authors: Volyntsev A. B. 
Published: July 2007

AbstractA mathematical model to examine the evolution of large dislocation complexes in crystals is proposed. The complexes are studied both, in the presence and after the removal of external mechanical stress. The problem is solved within the framework of continuous dislocation distribution with account of elastic long‐range interactions and thermal activation of dislocation movement.
High Pressure Structural Phase Transition in BaSe and BaTe
Authors: Rao B. Srinivasa , Sanyal S. P. 
Published: July 2007

AbstractThe structural phase transition due to high pressure in BaSe and BaTe is investigated for the first time using an interionic potential approach, based on the shell model formulation. The model parameters are derived using dielectric properties. The results show good agreement with experiment. The nature of the force constants at equilibrium and high pressure is discussed.
Multivalued μ‐Acoustoconductivity of Semiconductors
Authors: Bugaev A. S. , Vakser A. I. 
Published: July 2007

AbstractThe phenomenon of the formation of multivalued ohmic sections in volt–ampere characteristics (VAC) of semiconductors with electrons heated by sound waves is predicted. The VAC and the switching process are shown to be governed by the sound wave intensity. A possibility for the experimental realization of the studied phenomenon is discussed.
Surface Phase Diagrams of an Amorphous Ferromagnet with Surface Crystallization
Authors: Kaneyoshi T. 
Published: July 2007

AbstractSurface phase diagrams of an amorphous ferromagnet with surface crystallization are studied by the use of the effective‐field theory with correlations. It is proposed that the surface crystallization of an amorphous ferromagnet may be an effective method for investigating surface magnetic properties of the system with a higher surface transition temperature than that of the bulk.
Position Space Renormalization Approach to Spin‐1 Quantum Chains
Authors: Campana L. S. , D'Auria A. Caramico , Esposito U. 
Published: July 2007

AbstractThe spin‐1 transverse Ising chain with a single‐site anisotropy is studied by means of a real space renormalization group method which treats in a unified way the ground state and the finite temperature extension. The tricritical behaviour at T = 0 is presented and a comparison is made with previous results.
Parametric Amplification of Acoustohelicon Waves in Semiconductors
Authors: Jat K. L. , Ghosh S. 
Published: July 2007

AbstractThe parametric amplification of acoustohelicon waves is analytically investigated in a longitudinally magnetised semiconductor of centrosymmetric nature. The threshold value of the pump electric field (EOth) and initial gain constants are obtained. The longitudinal magnetic field decreases the required magnitude of (EOth) for the excitation, whereas it increases the gain constants. Numerical analyses are performed for an InSb crystal at 77 K duly irradiated by frequency‐doubled pulsed 10.6 μm CO2 lasers. It is found that the gain constants for both the couplings (gb) and for piezoelectricity only (gp) are nearly equal and approximately 100 times higher than that for deformation potential coupling (gd).