bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interionic Forces and Elastic Properties of Na2S
Authors: Agnihotri Neeta , Singh R. K. , Sanyal S. P. 
Published: July 2007

AbstractAn interionic potential model is proposed for crystals with antifluorite structure which consists of long‐range Coulomb and three‐body interactions (TBI), and short‐range dispersive and repulsive interactions up to second‐neighbour ions. This potential is used to calculate the cohesive energy, second‐order elastic constants, and their pressure derivatives of Na2S. The calculated values of elastic constants and cohesive energy agree well with their measured data which shows that the TBI contribute significantly to these properties.
Properties of the Exciton–Phonon System in a Magnetic Field
Authors: Gu Shi‐Wei , Zhou Yu‐Kui 
Published: July 2007

AbstractThe properties of excitons for a polar crystal in a weak magnetic field are discussed by using a perturbational method. When the interaction between phonons with different wave vectors in the recoil effect is neglected and a slow motion of the exciton is assumed, the electron–hole effective potential, the self‐trapping energy of an exciton, and the renormalized masses are derived.
Vibrational Spectra of Crystals with Sheelite Structure and the Solid Solutions on Their Basis
Authors: Nagiev V. M. , Efendiev Sh. M. , Burlakov V. M. 
Published: July 2007

AbstractIR‐reflection spectra of sheelite‐type crystals, XMeO4, where X = Ca, Pb: Me = Mo, W, and solid solutions on their basis are investigated. The obtained spectra are treated under the program: dispersion oscillator model – Kramers‐Kronig analysis. Frequency evolution and the decay of natural vibrations by substituting the metal atoms both inside the MeO tetrahedron and beyond of it are also studied. It is shown that the IR‐active vibrational spectrum of sheelite‐type crystals considerably depends on X‐type atoms (Ca or Pb). In solid solutions, while substituting Ca or Pb, some of vibrations in the spectrum reveal two‐ or three‐mode character of rearrangement. But the replacement of Mo by W does not lead to the formation of local vibrations, and the spectrum is found to be rearranged as a spectrum of single‐mode character.
Off‐Symmetry Phonon Frequencies of Copper
Authors: Chopra K. K. , Bouarab S. 
Published: July 2007

AbstractA simple phenomenological model is applied to interpret the experimentally measured off‐symmetry phonon frequencies of copper. It is emphasized that a truly acceptable theoretical model should not only give good results in the symmetry directions but must also be capable of a satisfactory reproduction of frequencies in the off‐symmetry directions.
Delocalized Positronium in Alkali Halides
Authors: Boev O. V. , Arefiev K. P. 
Published: July 2007

AbstractThe Bloch state of positronium in alkali halide crystals is considered. Interactions of positronium with the crystal field and with acoustic phonons are taken into account using perturbation theory. The effective mass of positronium in alkali halides is determined theoretically for the first time. Influence of these interactions on the positronium features in a crystal is discussed. The results obtained are in good agreement with available experimental data.
X‐Ray Photoelectron Spectra of Ag, Ga, In, and β‐Sn Metals Multielectron Excitations
Authors: Scrocco Marisa 
Published: July 2007

AbstractInformation on the final‐band energies of metals to relate to theoretical models can be usefully obtained from high‐energy photoemission spectra (XPS). The satellites present in the valence and core regions of Ag, Ga, In, and β‐Sn are assigned to multielectron excitations and compared with transition energies extracted from band structure calculations.
Optical Detrapping in Molecular Crystals. II. Second Conduction Band
Authors: Petelenz P. 
Published: July 2007

AbstractA possibility of optical detrapping to the second conduction band is investigated. A simple model is proposed to account for the coupling between the trap and band states. The coupling (when operative) is shown to shift the apparent distribution of trap depths towards greater values. Conclusions are utilized to propose a new experiment to locate the second conduction band of the anthracene crystal, and to probe its properties.
Phonons in Face‐Centred Cubic Calcium and Strontium
Authors: Singh S. P. , Rathore R. P. S. 
Published: July 2007

AbstractThe axially symmetric and unpaired forces are employed to analyse the phonon dispersion and elastic behaviour of face centred cubic calcium and strontium which have so far not been studied adequately. The model with three parameters predicts the results which agree marvellously with the recently measured data.
Magnetic State of Crystals with Dislocations
Authors: Karnaukhov I. N. , Zhuravlev A. F. 
Published: July 2007

AbstractThe inhomogeneous elastic fields of linear dislocations can lead to the formation of the noncolinear magnetic structure in the magnetic crystals under consideration. This structure is calculated in the frame work of the phenomenological approach; its localization region is determined and its formation criteria are discussed. The influence of the dislocation dilatation on the line width of the FMR and NMR is calculated also.
On the Damping of the Excitonic Polaritons
Authors: Cam Hoang Ngoc , van Hieu Nguyen , Viet Nguyen Ai 
Published: July 2007

AbstractThe general properties of the damping constants of polaritons in the two‐branch and three‐branch models are considered in the framework of the Green's function method. In particular, the expressions for the damping constants of the polaritons in terms of those of the excitons are established.
EPR Powder Spectra of Low‐Symmetric Mn2+ Complexes in Aragonite Lattice
Authors: Lech J. , Ślęzak A. , Bójko I. 
Published: July 2007

AbstractElectron paramagnetic resonance of Mn2+ ions in polycrystalline samples of natural aragonite containing about 100 ppm Mn impurities is studied at X‐ and K‐band. The parameters of the rhombic spin Hamiltonian estimated from the “powder” spectrum are found to be in a good agreement with the parameters obtained with single crystals. It is shown that satisfactorily accurate values of the spin Hamiltonian parameters can be extracted without the use of a simulating method, even in the case of the rather complex “powder” spectrum recorded at X‐band.
Analysis of Photoelastic Behaviour of Fluorite‐Structure Crystals
Authors: Dutt N. , Sharma O. P. , Shanker J. 
Published: July 2007

AbstractAn analysis of the photoelastic behaviour of fluorite‐structure crystals is performed by considering the existing theories of electronic polarizabilities of ions. On the basis of experimental and theoretical information available for electronic polarizabilities it is assumed that the change in polarizability due to strain under the effect of hydrostatic pressure is mainly arising from the change in anion polarizability. Values of strain polarizability parameters and volume derivatives of refractive index or electronic dielectric constant are evaluated and compared with experimental data for CaF2, SrF2, BaF2, PbF2, Sr(NO3)2, Ba(NO3)2, and Pb(NO3)2 crystals.
General Theory of Secondary Radiation in Condensed Matter
Authors: Lang I. G. , Pavlov S. T. , Prokaznikov A. V. , Goltsev A. V. 
Published: July 2007

AbstractA general theory is given accounting for the secondary radiation which is excited in condensed matter exposed by light at finite temperatures, T ≧ ħωs, where ωs is the radiation frequency. The formula which is derived for a light scattering tensor of rank four, is similar to that obtained by Kubo for the conductivity tensor. It allows for all types of interactions possible within the scattering medium. The obtained results are compared to conclusions in the cases of either low, T ≪ ħωs, or T ≥ ħωs temperatures.
Calculation of the Change in Knight Shift Due to Zn, Ga, and Ge Impurities in Copper
Authors: Gerbeth G. , Mrosan E. , Zeller R. , Dederichs P. H. 
Published: July 2007

AbstractStarting from a self‐consistent determination of the scattering properties of localised substitutional impurities the change in Knight shift in dilute alloys is calculated. The free‐electron theory of Daniel and Blandin is generalized to the case of the spherical band approximation. Numerical results are presented for Zn, Ga, and Ge impurities in a Cu host.
The Theory of Auger Spectra from Alloys. The Effect of Electron Correlations in Partially Filled Narrow Bands
Authors: Drchal V. , Kudrnovský J. 
Published: July 2007

AbstractThe effect of electron correlations on the Auger spectra from the substitutionally disordered narrow‐band metal alloys with partially filled bands is studied within the degenerate Hubbard model. Perturbation theory is used limited to the second order in U/w (U Coulomb integral, w bandwidth) for the calculation of the one‐particle Green function, and the ladder approximation for the two‐particle Green function. The effect of disorder is included within the single‐site approximation. The theory is illustrated on a simple model of the copper‐nickel alloy.
Spin Anisotropy and Critical Exponents for a Heisenberg System A Renormalization Group Approach
Authors: Fakioǧlu S. 
Published: July 2007

AbstractFirstly the renormalization group technique is applied to an isotropic Heisenberg spin system with long‐range interaction and a set of critical exponents are calculated. These exponents are expressed in terms of a potential parameter s̀. All critical exponents except β, the magnetization exponent, depend on s̀. Secondly, the anisotropy is considered and the related crossover exponent φ is evaluated. This later parameter turns out to be equal to γ, the susceptibility exponent, as predicted by some authors.
The Surface or Interface Polaron in Polar Crystals. III. The Phase‐Transition‐Like Transition for the Surface Polaron
Authors: Jin‐sheng Pan 
Published: July 2007

AbstractThe behaviour of the surface polarons in polar crystals is taken into account by making use of the Bogolyubov inequality. The results show that the ground state energy, effective mass, and the effective potential energy of the surface polarons are dependent on the temperature. For the strong coupling surface polaron, when the temperature approaches a certain critical value T0, there exists a phase transition from the polaron to the free electron; but for the weak coupling case, such a phase transition does not exist.
Structure and Bonding in Cubic IV–VI Crystals VI. Acoustic and Optical Deformation Potentials
Authors: Enders P. 
Published: July 2007

AbstractWithin the six‐band p‐model by Volkov et al. the acoustic and optical deformation potentials for the band‐edge states at the L‐points of the Brillouin zone are derived. Numerical results are obtained by means of geometrical arguments and chemical trends of tight‐binding parameters. These agree well with experimental and other theoretical results for the optical deformation potentials, but not for the acoustic ones. The conclusion in II on the smallness of the average interband‐optical deformation potentials is confirmed.
Electronic Properties of the Liquid TlGeTl2Te4 and TlSnTl2Te4 Systems
Authors: Ishikawa H. , Aoyama M. , Uemura O. , Satow T. 
Published: July 2007

AbstractMeasurements of the electrical conductivity, the magnetic susceptibility, and the thermoelectric power for the liquid TlGeTl2Te4 and TlSnTl2Te4 systems are made in wide temperature and composition ranges. It is observed that the conductivity for both systems falls near the composition of 80 mol% Tl and the diamagnetic susceptibility also shows a maximum at the corresponding composition. The thermoelectric power changes its sign around this composition. The ratio of real and free electron density of states at the Fermi level for both systems is close to 0.3 around the above mentioned critical composition, and at other compositions the value rises up to more than that. These electronic properties are discussed in the light of current transport theories employed in liquid semiconductors.
Transient Ie Centres in Alkali Halides
Authors: Jacobs G. 
Published: July 2007

AbstractTemporary infrared absorption bands are created in NaCl, KCl, RbCl, and KBr when nominally pure X‐ray coloured crystals are irradiated in the F band at low temperatures. This absorption shows a zero‐phonon line and a very detailed phonon structure. Some properties such as thermal decay, optical bleaching with polarized light, influence of impurities, and shape of the zero phonon line are studied.
One‐Particle Crystal Field Hamiltonians
Authors: Adam S. , Adam Gh. , Corciovei A. 
Published: July 2007

AbstractSystematic derivation of the one‐particle crystal field Hamiltonians is given for all possible site symmetries in crystals. Distinct parametrizations are found to occur only for the eleven Lauesymmetry groups, 1, 2/m, mmm, 4/m, 4/mmm, 3, 3m, 6/m, 6/mmm, m3, and m3m. The functional dependence of the Hamiltonian on the choice of the coordinate axes is also investigated. Its importance in proving, by numerical means, the correctness of the computed f‐electron energy levels in crystals is illustrated on an example.
Real‐Space Properties of Transition Dipole Matrix Elements in Semiconductors
Authors: Czajkowski G. , Balslev I. 
Published: July 2007

AbstractThe real‐space properties of the transition dipole matrix elements in semiconductors are studied theoretically. The results are expressed in terms of conventional band edge characteristics (such as the momentum matrix element and the band structure) and used in the coherent wave approach developed recently by Stahl. Simple isotropic bands lead to a real‐space behaviour of the dipole density described by a spherical evanescent wave. Anisotropic band extrema and saddle points are also studied.
Local‐Density‐Functional Approach to the Electronic Structure of Rhodium under High Pressure
Authors: Petrů J. 
Published: July 2007

AbstractThe electronic structure of f.c.c. rhodium at three lattice constants corresponding to an ambient pressure up to 650 kbar is derived using self‐consistent density‐functional calculations by the quadratic‐augmented‐plane‐wave method. Comparisons are made for the pressure‐dependent behaviour of the energy bands and the charge distribution, as well as the total and angular‐momentum‐decomposed densities of states inside the muffin‐tin spheres. Harrison's semiempirical parametrisation is tested against these first principles results.
Nonlinear Theory of the Photomagnetoelectric Effect with a Square‐Root Relationship between Carrier Densities
Authors: Augelli V. , Vasanelli L. , Leo M. , Leo R. A. , Soliani G. 
Published: July 2007

AbstractThe theory of the photomagnetoelectric effect (PME) is studied in the case in which the recombination mechanism gives rise to a square‐root relationship between carrier densities. The nonlinear continuity equation is solved and analytical expressions of short‐circuit PME current IPME and photoconductance ΔG are found in the case of strongly absorbed light. The dependence of IPME and ΔG on the light intensity is studied by assuming as an example a three level recombination model. The main results of the analysis is that the IPME vs. ΔG behaviour shows the same power law as the charge carrier do.
On the Magnetic Properties of Gd1−xRExAl2 Alloys
Authors: Witański K. 
Published: July 2007

AbstractDisordered alloys of RE metals are considered and a general formula for paramagnetic susceptibility and the equation for Curie temperature are derived. The previously derived effective exchange interaction is assumed and the crystal electric field is taken into account. Molecular field and Hart‐ree‐Fock approximations combined with the coherent potential approximation are used. The results obtained are applied to Gd1−xRExAl2 (RE = Dy, Ho, Er) and discussed together with the experimental data.
Microscopic Model for the Relaxation and Excitation of Localized Spin Waves
Authors: Lin J. T. , Li Z. Y. 
Published: July 2007

AbstractA microscopic Hamiltonian with long‐range spin‐spin interactions showing the host‐spin‐induced energy relaxation and frequency shift of the impurity spin is studied within a Markovian process. The localization conditions and the associated dispersion laws of spin waves in ferromagnetic and antiferromagnetic systems containing one or two impurities are investigated at various domains of the exchange integrals and the spin amplitudes. The correspondence between the localized spin waves and lattice vibrational modes is analyzed. Finally, the energy absorption and the possible mechanism for selective excitation of a localized magnon are discussed based on a quantized Hamiltonian which includes the impurity‐host coupling and their interactions to an external magnetic field with frequency near resonance to that of the localized active mode.
A Dynamical Theory for a Disordered Hubbard Chain far from Equilibrium. II. The Low‐Field Case
Authors: Heiner E. 
Published: July 2007

AbstractFor a finite chain of strongly correlated electrons a nonlinear transport theory is treated. The time dependent behaviour of the expectation values for singly and doubly occupied states and the local and total current densities are calculated for oscillating boundary conditions in the asymptotic limit (t → ∞).
51V NMR of Amorphous and Crystalline V‐Zr Alloys
Authors: Bakonyi I. , Han K.‐S. , Schone H. E. 
Published: July 2007

AbstractResults of 51V NMR Knight shift and linewidth measurements are described for thin films of V100−xZrx b.c.c. crystalline (x = 6.4 and 8.4) and amorphous (x = 17.2, 28, and 46.4) alloys prepared by rf sputtering onto copper substrates. The field dependence of the linewidth and, for x = 28 and 46.4, heat‐treatment effects were also considered. Based on these experimental data, quadrupole effect, electronic structure, and chemical short‐range order of amorphous V‐Zr alloys are discussed.
Effects of the Crystal Field in the Spectra of Iron Group Impurities in ZnSe
Authors: Biernacki S. W. 
Published: July 2007

AbstractThe many‐electron crystal field term states are calculated with account of the symmetry dependent deformation of the 3d orbitals and of the dependence of one‐electron energies on the spin orientations. It is shown that the one‐electron 3d orbitals of symmetry t2 are extended with respect to orbitals of symmetry e by 1 to 4%. The relative deformation depends on the ratio of a σ‐type resonant integral to a π‐type resonant integral.
Atomic Ordering in Multicomponent Alloys
Authors: Dabrowski L. 
Published: July 2007

AbstractThe pair interaction model of binary alloys is generalized to cover the case of an arbitrary number of components. Both, the interaction radius and the number of short‐ and long‐range ordering parameters are unlimited. The problem is solved by applying the high‐temperature series expansion method, using a new diagram technique, to calculate the fluctuation potential.
Many‐Body Contribution to the Energy of Metals with B.C.C. Lattice
Authors: Bogdanov V. I. , Fuks D. L. 
Published: July 2007

AbstractThe Fourier transforms of covalent charge density and the contribution of the third and fourth order of perturbation series for the energy (E) of alkali and some transition metals are calculated on the basis of self‐consistent Brillouin‐Wigner pseudopotential perturbation theory. The scattering of electrons on the planes of the first and second Brillouin zones in the b.c.c. lattice is taken into account. It is shown that the value E is of the same order as the heat of polymorphic transition. The convergence of perturbation series in pseudopotential theory for the calculation of transition metal energy with Animalu's form‐factors is investigated.
Wavelength Modulated Spectra of α‐Ag0.7Zn0.3 near the Optical Absorption Edge
Authors: Stearns R. , Braunstein R. , Muldawer L. 
Published: July 2007

AbstractThe optical properties of α‐phase Ag 0.7Zn0.3 are determined near the optical absorption edge. This alloy composition dampens the sharp Ag‐plasma resonance. The band shifts which are observed are in qualitative agreement with calculations which are performed for the similar alloy, α‐Cu0.7Zn0.3.
Photoinduced Optical Absorption of Cr4+ in Semi‐Insulating GaAs:Cr
Authors: Ulrici W. 
Published: July 2007

AbstractThe optical absorption of Cr4+ created during illumination with hv > 0.75 eV in semi‐insulating GaAs:Cr is investigated at low temperatures (≤ 150 K). Analyzing the concentrations of Cr2+, Cr3+, and Cr4+ during illumination and measuring the excitation spectrum of Cr4+, the creation mechanism of photoinduced Cr4+ conclusively proved to be the two step process Cr3+ + hv → Cr2+ + holevb and holevb + Cr3+ → Cr4+. The concentration of photoinduced Cr4+ is measured in dependence on the contents of Cr2+ and Cr3+ present in the samples before illumination, on temperature, and on illumination intensity. Its time dependence of rise after switching on and of decay after switching off the illumination is measured under various conditions. The results are interpreted using dynamic equations for the concentration of Cr2+, Cr3+, and Cr4+ during illumination basing on the assumption that only excitation and capture processes via the valence band contribute to the formation of photoinduced Cr4+ and that the tunneling process Cr4+ + Cr2+ → 2 Cr3+ is responsible for its decay.
Electroabsorption for Deep Level to Band Transitions Accompanied by Multiphonon Processes
Authors: Schenk A. , Enderlein R. , Suisky D. 
Published: July 2007

AbstractThe electroabsorption spectrum for optical transitions from a deep level to a band accompanied by multiphonon processes is calculated within the Lucovsky model. The line shape turns out to be highly sensitive to the Huang‐Rhys factor and to the ratio of electrooptical and phonon energy.
The Sextic Polynomial of Crystal Elasticity
Authors: Head A. K. 
Published: July 2007

AbstractIt has previously been proved that the sextic polynomial of crystal elasticity is not explicitly solvable for arbitrary elastic constants and directions except for hexagonal symmetry. In the case of cubic symmetry there are special elastic constants known for which the polynomial is solvable for all directions. A search is made over the range of physically significant elastic constants for any further special cases. It is conducted with an extension to Galois theory that gives a measure of how far any particular polynomial is from being solvable rather than just a yes‐no result. No further special elastic constants are found and it appears very probable than none can exist although there is not a strict proof of this.
Photoelectron Diffraction and Band Structure Effects in ARXPS from the Valence Bands of GeS
Authors: Chassé T. , Berg U. , Brümmer O. 
Published: July 2007

AbstractX‐ray photoelectron spectra of the valence band region of GeS are measured in dependence on polar and azimuthal angle. The anisotropy of the valence band structures is due to both, influences of initial state wave function and photoelectron diffraction. By these means in addition to the symmetry character of initial states the atomic nature of different valence band peaks can also be explained.
The Electronic Configuration of 121Sb in Semiconductors
Authors: Weyer G. , Andreasen H. , De Waard H. 
Published: July 2007

AbstractIsomer shifts of the 37 ke V Mössbauer transition in 121Sb are determined for 121Sb constituents and impurities in III‐V and II‐VI compound semiconductors. Radioactive 121Xe isotopes decaying to 121Te, the 121Sb‐parent isotope, were implanted at the ISOLDE facility at CERN. The nature of the electronic configuration of Sb‐isoelectronic and Sb‐donor and ‐acceptor impurities in semiconductors is discussed in terms of bond hybridization and ionicity. The influence of structural relaxation is pointed out.