bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Analysis of the Nonresonant Interband Faraday Rotation in Ge and Si
Authors: Metzdorf J. , Kessler F. R.
Published: July 2007

The Kramers‐Kronig transform of the purely absorptive real part Re of the nondiagonal component of the complex dielectric tensor is applied for the first time to assign quantitatively the contributions from various individual interband transitions (≦ 4.6 eV) to the dispersive interband Faraday rotation (IFR) in Si and Ge. The data of Re needed are determined from measurements of Faraday ellipticity and complex Kerr effect, respectively. In particular, the following problems could be clarified: (i) the origin of the nonresonant change in sign of the rotation in Ge which is due to the competition mainly between negative contributions from E0, E1 + Δ′0 transitions and a positive contribution from E1 transitions; (ii) the relative contributions from indirect transitions in Si. (iii) The present results are generally useful for studying and interpreting the effect of doping and, moreover, give indication of a systematic trend in how various critical points may contribute to the nonresonant IFR in different semiconductors.
Radiation Damage of Ni2+‐Doped NH4MgPO4 · 6 H2O
Authors: Chowdari B. V. R. , Ravisekhar Y. , Muralikrishna C.
Published: July 2007

An optical absorption study of NH4MgPO4 · 6 H2O doped with Ni2+ shows that Ni2+ substitutes for Mg2+ in the lattice. This spectrum is fitted to the Liehr and Ballhausen scheme for a 3d8 ion in Oh surroundings. A correlated ESR and optical absorption study of these crystals on X‐ or γ‐irradiation at room temperature indicates the formation of Ni3+ and NH3+ radicals. The NH3+ center is found to have an isotropic g and AH and an anisotropic AN. This center is also produced in undoped crystals with lower yield. Ni3+ centers are found to be paramagnetic and exhibit their characteristic optical absorption bands.
Application of BBGKY Equations to the Study of Ordering in Alloys
Authors: Stark Yu. S. , Steinberg A. S.
Published: July 2007

The chain of the BBGKY (Bogolyubov‐Born‐Green‐Kirkwood‐Yvon) equations for lattice systems is obtained. These equations differ greatly from those for the continuous case and can be used in the theory of the Ising model. Different characteristics of ordering in alloys are computed using these equations: phase transition temperature, correlation parameter, correlation functions at great distances. The results obtained are in good agreement with other theories.
Evaluation of the Grüneisen Parameter for NaCl‐Structure Alkali Halide Crystals
Authors: Shanker J. , Singh K.
Published: July 2007

The Grüneisen parameters for sixteen alkali halide crystals with NaCl structure are calculated with the help of the model recently developed by Migault and Romain. This model takes into account the volume dependence of Poisson's ratio. The derivatives of pressure with respect to volume are estimated by adopting different potential functions suitable for ionic crystals. The results obtained in the present study are discussed and compared with experimental data and other recent investigations.
CPA Study of the Electrical Conductivity for Various Percolation Models
Authors: Kolley E. , Kolley W. , Fehske H.
Published: July 2007

Transport properties are examined for randomly disordered systems comprising a mixture of conducting and insulating components. The tight‐binding models on a s.c. lattice are specialized to purely diagonal disorder, off‐diagonal disorder of the multiplicative and additive type, also in the presence of electron‐electron interaction; the percolation limits are reached by the breaking of inter‐ or intra‐species links. The effective medium is provided by the CPA (coherent potential approximation) and its extended version ODCPA, if necessary combined with the Hartree‐Fock approximation. The dc conductivity σ vanishes at a critical concentration xc of inaccessible sites at fixed Fermi energy. The ODCPA involving vertex corrections refers to localization in the middle of the band. Numerical σ(x)‐results are presented.
Electron Structure and X‐Ray Absorption Spectra of Potassium Chloride I. Band Structure Approach
Authors: Gegusin I. I. , Datsyuk V. N. , Vedrinskii R. V.
Published: July 2007

The conduction band (CB) structure of potassium chloride in a rather wide energy region is calculated by means of the augmented plane wave (APW) method. The important features of CB are the hybridization and interaction of nearly free electron bands with K d‐ and Cl d‐bands. These effects lead to the appearance of many contrast peaks in the energy distribution of the density of K p‐and Cl p‐states. These distributions are compared with the experimental X‐ray K‐spectra in KCl. As a result of this comparison it is concluded that the band theory of an ideal crystal ground state is insufficient for an adequate quantitative explanation of the X‐ray absorption spectra in alkali halides. The assumption is made that one must take in account the deep core hole influence on the final‐states spectrum.
Integral Representation of the Incoherent Field in Disordered Matarials. I. Current Balance, Density‐of‐States Test, and New Mobility Formula
Authors: Lenk R.
Published: July 2007

For a disordered material composed of many point‐like single scatterers a representation considered first by Foldy for the autocorrelation function of the incoherent field guarantees in a general way a loss‐free total current which consists of a coherent and an incoherent part. This demand fixes uniquely the representation mentioned. An exact connection with the density of states allows for an additional test independent from the current balance. By the generalizing inclusion of a driving force into the coherent wave equation a non‐classical prescription for the calculation of the mobility is derived. In three as well as in one dimensions the new formula reproduces exactly the classical limit for a large mean free path. For a filled band it yields no current. In the case d = 1 for short mean free paths the conductivity departs significantly from its classical value, but not for d = 3.
Cyclotron Masses and Many‐Body Effects in Transition Metals
Authors: Schmidt B. , Antonov V. N. , Mrosan E.
Published: July 2007

Cyclotron masses for extremal orbits in Nb, Ta, W, Ir. Pt, and Au are calculated using a relativistic APW band structure. The integration along the extremal electron orbits over the Fermi surface is performed numerically using the well known tetrahedron method. Results are compared with experimental values obtained from the de Haas‐van Alphen investigations. The influence of manybody effects is discussed.
Experimental Check of Different Additional Boundary Conditions in Case of Spatial Dispersion
Authors: Skettrup T.
Published: July 2007

Reflection and transmission spectra are computed for the A‐ and B‐excitons in ZnO which exhibit spatial dispersion. The different additional boundary conditions are tested by comparison with the corresponding experimental spectra. Without exciton free surface layer the Pekar condition (perfect reflection and vanishing of excitonic wave function at the surface) yields the best fit to the experimental spectra. The agreement is improved if the damping is assumed k‐dependent. With exciton free surface layer included it turns out that the best agreement is obtained if only part of the excitonic wave function is reflected from the surface. Without k‐dependent damping about 50% must be reflected, and with k‐dependent damping about 70% of the excitonic wave function must be reflected from the surface. A simple method is also described from which the transmission spectra of spatially dispersive crystal slabs with exciton free surface layers can be computed.
Mixed Valence State and Metal–Non‐Metal Transition of KCP
Authors: Nagasawa H.
Published: July 2007

On the basis of the recent XPS results, which established the existence of Pt4+ ions in KCP at 153 K, a new model is proposed of platinum valence state in KCP, that is, a valence mixing state of 0.85 Pt2+ and 0.15 Pt4+ ions as a ground state and Pt3+ ionic state as an excited state. The experimental results of the conductivity, the spin susceptibility, the NMR relaxation, the EPR relaxation, and the neutron scattering are discussed according to the present model.
An Assessment of the High‐Energy Approximation in the Dynamical Theory of Electron Diffraction
Authors: Kim H. S. , Sheinin S. S.
Published: July 2007

The high energy approximation in the dynamical theory of electron diffraction is assessed for both the symmetrical Laue and non‐symmetrical Laue cases. In order to carry out this assessment an exact form of the theory, expressed as an eigenvalue equation, is first developed. The results obtained show that for the normal operating conditions which prevail in the electron microscope examination of crystals, the errors introduced by the high‐energy approximation in the symmetrical Laue case are small. In the non‐symmetrical Laue case, the errors obtained for strong beam diffraction conditions are also small. For weak beam diffraction conditions, however, significant errors can be obtained.
Temperature and Coupling Strength Dependence of Polaron Effective Mass and Radius
Authors: Fedyanin V. K. , Rodriguez C.
Published: July 2007

Polaron effective mass and radius are investigated by using path integral methods. The calculations are performed in the framework of the variational principle for the free energy. At low temperatures, a generalization of Feynmans expression for the effective mass and an expression for the polaron radius at arbitrary coupling are obtained. It is shown that at low temperatures, the effective mass increases and the radius decreases with increasing temperatures. This behaviour of the effective mass agrees satisfactorily with cyclotron resonance experiments and is easily explained qualitatively.
Hyper‐Raman Scattering by Phonons and Mixed Polaritons in a Calcite Crystal
Authors: Denisov V. N. , Mavrin B. N. , Podobedov V. B. , Sterin Kh. E.
Published: July 2007

The polarized hyper‐Raman spectra of a calcite crystal in different scattering geometries are obtained. Two silent A1u‐vibrations at 227 and 1085 cm−1 as well as infrared active vibrations are found. The upper branch of mixed A2u‐polaritons and their resonance with Eu‐vibrations is investigated. The calculation of mixed polariton dispersion curves is presented.
Partial Structure of Liquid Sodium—Cesium Alloys
Authors: Rao R. V. Gopala , Satpathy B. M.
Published: July 2007

The partial structure factors defined by Ashcroft and Langreth and also the number–number, number–concentration, and concentration–concentration structure factors of Bhatia and Thornton are calculated for liquid sodium–cesium alloys at various concentrations with a square‐well potential. The total structure factor obtained from these partials compares very well with experimental results. Isothermal compressibilities obtained from the partial structures in the long wave limit are also found to compare satisfactorily with those calculated from sound velocity data.
On the Nature of the Oscillating Behaviour of the Free Induction Decay
Authors: Sabirov R. Kh. , Vinukhov I. A.
Published: July 2007

Evans and Powles' theory is used for the investigation of the transverse autocorrelation and pair correlation functions for quantum spins with truncated dipolar interaction in a simple cubic lattice. It is shown that the oscillating behaviour of the free induction decay (FID) function is determined by the contribution of the pair correlation functions in the FID function describing the evolution of the transverse magnetization. The role of the orientational dependence of the dipolar interaction constants with the appearance of oscillations in the FID is investigated. Estimates of the FID function for a model Hamiltonian are made.
Density‐Functional Theory of the Pressure Distribution at Metal Surfaces
Authors: Heinrichs J. , Magain P.
Published: July 2007

Density‐functional theory is used to calculate the exact spatial distribution of the pressure at a planar jellium surface at various densities. A comparison with a local density approximation and with other descriptions of pressure in inhomogeneous systems is briefly discussed.
Bound Exciton Time Decay and the Auger Effect in Zinc Telluride
Authors: Schmid W. , Dean P. J.
Published: July 2007

The measured lifetimes for the decay of excitons bound to a variety of neutral acceptors in ZnTe reveal a complex trend with increase in the acceptor binding energy EA. The lifetimes increase with EA up to > 0.15 eV, in a manner expected for radiative transitions because of the decrease in the giant oscillator strength of the transition with increase in localisation of the electronic particles. Although rather few well‐identified acceptor species are available with EA > 0.15 eV, it is clear that this trend of lifetime is sharply reversed in this range, as expected if the Auger (non‐radiative) recombination rate overtakes the decreasing radiative rate near EA ≈ 0.15 eV. Comparisons with other available data from direct and indirect gap semiconductors support this relationship between the transition rates. Therefore, a much more significant role for Auger recombinations is found in bound exciton and other transitions involving more than two electronic particles than previously recognised for direct gap semiconductors.
Double Structure of AX and AT Emissions in Low‐Doped KI:TI+ Crystals
Authors: Benci S. , Fermi F. , Reverberi R.
Published: July 2007

The emission spectra of low‐doped crystals (up to 10 ppm) of KI:TI+ (as‐received, quenched and slowly cooled from 500 °C) show the presence of a center, probably a dimer center, that absorbs at λ > 2900 Å at LNT and emits in the range of the AT and AX emissions of the monomer. The emissions of this center affect the emission spectra at T > LNT also for excitation at λ < 2900 Å.
On the S‐Shaped Characteristic of Semiconductors at Low Temperature
Authors: Proctor W. G. , Lawaetz P. , Marfaing Y. , Triboulet R.
Published: July 2007

It is shown that when the energy level pattern of an impurity in a semiconductor is reduced to the ground state and one excited state, and when the occupation of this excited state is a necessary step for both impact excitation and relaxation, an S‐shaped dependence of the carrier density upon the electric field dependent impact parameters is obtained. Simple functions of the impact parameters are measured against electric field for ZnTe at 77 K using the above theory.
Conversion of Impurity—Vacancy Complexes under γ‐Irradiation and Subsequent F Band Bleaching in KCI:Eu2+
Authors: Mladenova M. , Malinovski A. , Georgiev M.
Published: July 2007

The ESR signal from I‐V complexes in KCI:Eu2+ is found to decrease markedly as a result of γ‐irradiation and to vary swing‐wise on subsequent F band bleaching at RT. The main bleaching process is explained by the superposition of Z1 centre formation and the revival of I‐V complexes following photostimulated recombination of F centres with I‐V‐trapped interstitials. Evidence seems also to be obtained for Eu+ formation at the initial bleaching stage.
X‐Ray Spectroscopic Study of Rare Earth‐Gallium Intermetallics RGa2
Authors: Prabhawalkar V. , Padalia B. D.
Published: July 2007

Rare earth‐gallium, RGa2 (R = La, Ce, Pr, Nd, Sm, Tb, Ho, Er, and Tm) intermetallic compounds are prepared and checked for single phase formation. The K‐absorption spectrum of Ga and the L3‐absorption spectrum of R in RGa2, are recorded photographically. A forbidden transition, 2P3/2 4f (unoccupied) is detected for TbGa2, DyGa2, HoGa2, and TmGa2 indicating the presence of a open 4f shell in these compounds. The measured chemical shifts exhibit linear relationship with theoretically estimated values ofeffective charges on the absorbingions. An attempt is made to calculated the edge shifts theoretically. The R‐Ga and Ga‐Ga bond lengths estimated using EXAFS methods show reasonable agreement with crystallographic data. The parameter, α, which is a measure of chemical bonding in the system, is evaluated using the graphical methodof Lytle, Sayers, and Stern.
Entropy of Mixing of Liquid Alloys
Authors: Singh P. , Khanna K. N.
Published: July 2007

An analysis of the concentration dependence of the entropy of mixing, based on the idea of excess volume formation on alloying the hard spheres of different diameters, is presented. Flory's formula for the entropy of mixing provides unsatisfactory results also due to incorrect estimation of excess volume formation in the theory.
Contributions to “Crystal Fields” from Electron Kinetic Energy Terms
Authors: Dixon J. M. , Chatterjee R. , McInnes J. A.
Published: July 2007

The magnitude of contributions to the B crystal field coefficient, from second‐order kinetic energy terms, is estimated and compared with the value from other sources. Its relative value is small and never greater than approximately 10%. If the parameters chosen in the paper for the 3s oxygen state are used, the contributions to B, B, and B are 1 to 2 cm−1.
Electrodynamics of a Spatially Dispersive Medium with Spherical Cavity
Authors: Kryuchenko Yu. V. , Sugakov V. I.
Published: July 2007

The exact solution of the problem of electromagnetic wave scattering by a spherical inclusion in a spatially dispersive medium is obtained. In comparison with well‐known results of the Mie theory of a medium without spatial dispersion the main new features are: (i) the frequency dependence of the scattering cross‐section is changed; (ii) the transformation of normal waves from one type into another takes place at the inclusion; (iii) the states bound to the spherical inclusion have finite lifetimes even in the absence of usual dissipative mechanisms. For some physical systems (excitons in CdS) the numerical calculations of scattering cross‐sections are performed. The frequencies and lifetimes of states bound to the spherical inclusion are also determined.
The Excitation Map of Surface Barrier Resonances III. Resonances at Tilted Incidence on the Ni(001) Surface
Authors: Solbrig H.
Published: July 2007

The excitation map (|det (I – RphS+−)| as a function of E, k|; Rph, S+− reflection matrices of the substrate and the barrier, respectively) is used for qualitatively treating the following aspects of surface barrier resonances: decomposition of complex resonance states with respect to their source effects (beam emergences), ground resonance and Bragg effects, resonance profile and resonance energy, and interaction and superposition of resonance processes.
Polarization Dependence of Two‐Photon Magnetoabsorption of the 1S Exciton in Cu2O
Authors: Fröhlich D. , Kenklies R.
Published: July 2007

The formalism for the two‐photon polarization dependence of a Γ state (Oh symmetry) in a magnetic field is developed. Experiments on the 1S exciton (yellow series) in Cu2O yield an unambiguous assignment of magnetic quantum numbers, thus allowing to determine g‐values.
Integral Representation of the Incoherent Field in Disordered Materials II. Hall Current and Thermoelectric Phenomena
Authors: Lenk R.
Published: July 2007

The theory developed in I is generalized by the inclusion of a magnetic field or of a temperature gradient. Also in these more general situations the theory exhibits internal consistency with regard to the representation of the Hall current and the Onsager symmetry for thermoelectric phenomena. The Hall coefficient departs from its classical value in the case of small mean free path and has unique sign.
Dipole Force Tensors of Vacancy‐Type Defects in α‐Iron
Authors: Ong C. K.
Published: July 2007

A computer simulation is made to calculate the dipole force tensors and relaxed volumes of vacancy‐type point defects in α‐iron, using a spline‐fit pairwise potential for α‐iron, derived by Johnson. The displacement fields around the point defects are also reported.
Influence of Electron‐‐Phonon Interaction on Electronic Heat Capacity of Nb
Authors: Zhdanov K. R. , Rakhmenkulov F. S.
Published: July 2007

The electronic heat capacity of Nb is obtained from the experimental specific heat data between 10 and 350 K. The heat capacity of the lattice is determined by using the available data on phonon density of states. It is shown, that the electronic specific‐heat coefficient is dependent on temperature. Comparisons are made with the theoretical works of Masharov and Grimvall. The qualitative fit is quite good.
Effective Interactions in Jellium Including Exchange
Authors: Brosens F. , Devreese J. T.
Published: July 2007

Explicit calculations are presented for the effective interactions in the homogeneous electron gas between two test charges, between an electron and a test charge, and between two electrons. The calculations are performed in the local approximation using existing theories for treating dynamical exchange effects in the dielectric response. The relation between these different approaches is discussed. The most remarkable result is that two recent dynamical local‐field corrections in the static limit give rise to an attractive effective electron–electron potential near q = 2kF, without the intervention of phonons.
Electron Structure and X‐Ray Absorption Spectra of Potassium Chloride II. Effect of a Core Hole in the Cluster Approach
Authors: Vedrinskii R. V. , Gegusin I. I. , Datsyuk V. N. , Novakovich A. A. , Kraizman V. L.
Published: July 2007

X‐ray K‐absorption spectra of potassium and chlorine for 27‐atom clusters KCl6K12Cl8 and ClK6Cl12K8 are calculated in the framework of the scattered wave method. The spectra obtained for the ground state of the cluster are in good agreement with infinite crystal ones which are calculated by the APW method. The dimensions of the cluster representative for the description of the X‐ray photoionization process in solids are discussed. The influence of the ls‐hole potential on the spectrum shape is investigated in the cluster approach. A fair correlation between the theoretical and experimental spectra is obtained. It is shown that it is necessary to take into account the deep hole potential for a correct calculation of X‐ray absorption cross‐sections.
Calculation of the Equilibrium Mean Charge of Helium Ions
Authors: Kaneko T. , Ohtsuki Y. H.
Published: July 2007

Z2‐oscillation of the equilibrium mean charge of 1 MeV He ions discovered by experiments is confirmed by calculating both the electron‐capture and ‐loss cross‐sections, employing two‐state atomic expansion method and Bron approximation, respectively. The calculations are in good agreement with the experimental results.
Bond Hybrids and the Structures of the Lanthanide Metals
Authors: Langley R. H.
Published: July 2007

The ideas developed by Altmann, Coulson, and Hume‐Rothery to relate bond hybrids to metal structures are extended to include treatment of the f orbitals. A discussion of the possible hybrids along with their application to the lanthanide metals will be considered.
Relative Stability and Structural Phase Transitions in Alkaline Earth Chalcogenide Crystals
Authors: Singh R. S. , Jain V. K. , Shanker J.
Published: July 2007

Using some recently developed interionic potentials the problem of relative stability and structural phase transition is studied in fifteen alkaline earth chalcogenides. The NaCl structure is found to be more stable than the CsCl structure for all the chalcogenides under study. This prediction is in agreement with the experimental facts. The cohesive energies and volume changes due to structural transformation are calculated and discussed in the light of experimental data.
Comments on the Pressure Variation of the Gibbs Energy for Bound and Unbound Defects
Authors: Varotsos P. , Alexopoulos K. , Nomicos K.
Published: July 2007

The pressure derivative v of the Gibbs energy g for “unbound” and “bound” defects (i.e. vacancies or interstitials attracted by aliovalent impurities) is studied. It is shown that for the formation and migration of defects the ratio v/g depends solely on well‐known macroscopic properties; applications are presented for self‐diffusion in f.c.c. and b.c.c. metals and for ionic conductivity of silver halides. In the case of ionic solids containing “bound” defects, a gradual variation of pressure results in the appearance of a transient polarization or depolarization current that maximizes at a certain pressure Pcr. The way of analysing this piezo‐stimulated current (PSC) spectrum is discussed. The fact that the value of Pcr does not have to coincide with the pressure at which fracture occurs provides a useful tool for applying PSC to geophysics.
The Influence of the Dynamic Jahn‐Teller Effect on the Phonon‐Scattering Mechanism at Acceptors in Semiconductors with Cubic Symmetry
Authors: Sigmund E. , Lassmann K.
Published: July 2007

Phonon scattering experiments of various types in cubic semiconductors doped with deep effective mass acceptors indicate an extra resonance scattering at some meV. It is shown, using Green's function and transformation techniques that these resonances are due to a dynamic Jahn‐Teller effect of the Γ8 acceptor ground state.
Magnetic Properties of Oxygen Monolayers Adsorbed on Graphite
Authors: Diep‐The‐Hung  , Motchane J. L.
Published: July 2007

The in‐plane collinear antiferromagnetic structure of two‐dimensional distorted triangular lattice of solid oxygen molecules is shown to have the origin in intermolecular magnetic dipole–dipole interaction. By including this dipolar interaction in the isotropic Heisenberg Hamiltonian the intermolecular exchange integrals are calculated between nearest and next‐nearest neighbours, using availale neutron scattering and X‐ray diffraction data of oxygen monolayer adsorbed on graphite. Temperature dependence of sublattice magnetization is also shown and discussed.
Coulomb (or Strong) Correlation Effects in the Band Structure of Eu2O3
Authors: López‐Aguilar F. , Costa‐Quintana J. , Muñoz J. S.
Published: July 2007

Two band‐structure calculations of Eu2O3 are performed, one of them in the metallic phase and the other in the semiconducting phase; the difference between the corresponding band Hamiltonians is the occupation potential U (r) that includes the Coulomb correlation effects. In both phases, the 4f occupied bands are mixed with the 2p bands; this fact broadens these 4f bands so that its calculation is possible in this complex crystal lattice T. In the semiconducting band structure, the 4f empty bands are localized in the d‐zone energy showing (4f, 5d) hybridization that produces a broadening still greater than for the 4f occupied bands. The semiconducting gap is Γ – H and its value is 3.7 eV.
Discrete Saturation Effects of the ESR Spectrum of H0 in CaF2
Authors: Hornos Y. M. M. , Panepucci H. , Magon C. J. , Terrile M. C.
Published: July 2007

Several experiments involving pulse saturation of ESR transitions of H0 in CaF2 are presented. The results are discussed and shown to arise from the mechanism of discrete saturation.
Electronic Energy Bands of Some AgMg, CuAl, and AlLi Alloys
Authors: Raychaudhuri M. , Chatterjee S.
Published: July 2007

The complex energy band structures of the substitutional alloys AgMg, CuAl, and AlLi are presented for 13 and 27 at% of Mg in AgMg, 5 and 15 at% of Al in CuAl, and 5 at% of Li for AlLi. The averaged T‐matrix approximation in conjunction with the KKRZ method is applied to the calculation of the complex energy bands and the Fermi surfaces of the alloys are evaluated from these data. The experimental optical spectra are discussed in the light of band to band transitions of the theoretically found band structures. The effect of charge transfer is also studied for a AgMg alloy with 27 at% Mg. The theoretically obtained Fermi surfaces are compared favourably with the experiment.
Effect of Magnetostatic Field on the Stimulated Raman Scattering of Transversely Polarized Electromagnetic Waves and Raman Instability in Semiconductor Plasmas
Authors: Ghosh S. , Agrawal V. K.
Published: July 2007

The stimulated Raman scattering of a large amplitude transversely polarized electromagnetic pump wave from both, the electron plasma wave and the molecular vibrations produced at a frequency equal to that of transverse optical phonon, is investigated in an n‐type semiconductor plasma. The general dispersion relation is obtained considering only the Stokes' component of the scattered electromagnetic wave in the presence of a large magnetostatic field applied at an arbitrary angle to the direction of propagation of the pump wave. The analysis is applied to both the cases of isotropic (B0 = 0) and magnetoactive (B0 ± 0) plasmas. The threshold electric field necessary for the onset of Raman instability and the growth rate of the unstable mode well above the threshold is studied. It is concluded that the threshold pump amplitude as well as the growth rate have strong dependence on the orientation of the magnetostatic field with respect to the wave vectors k, k1 and its magnitude.
Compression Effect on the Lattice Dynamics of Alkali Metals
Authors: Soma T. , Kimura Y. , Kagaya H.‐M.
Published: July 2007

The lattice dynamics of alkali metals under pressure is investigated using the second‐order perturbation and the local Heine‐Abarenkov model potential. Then, using the long‐wave phonon‐velocity method, the bulk modulus, and the shear elastic constants under compression are studied theoretically.
Thermodynamics of Aluminium and Magnesium‐Base Interstitial Solutions II. Energy of Mixing of Binary and Ternary Alloys
Authors: Bogdanov V. I. , Mikhailov A. V. , Fuks D. L.
Published: July 2007

The energy of disordered solid interstitial solutions and the energy of mixing in these solutions up to the second order of perturbation theory in pseudopotential is discussed. The correspondence of items, defining the band structure energy in interstitial and substitutional solutions is established. A comparative analysis of the contributions to the total energy of boron and carbon solutions in aluminium is performed. Numerical calculations show that the increase of impurity concentration results in the relaxation of elastic stresses, which is indicated by the decrease of quasielastic Fourier‐transform forces. The applicability of the perturbation theory in pseudopotentials limited to second‐order terms in the calculations of the energy of mixing in dilute interstitial solutions is analyzed. The alloying effect on the positive energy of mixing is discussed.
Optical Investigations on HfCxN1−x Compounds
Authors: Fluck F. W. , Geserich H. P. , Politis C.
Published: July 2007

A report is given on the spectral reflectance of polycrystalline samples of HfCxN1‐x compounds in the energy range between 0.1 and 6.2 eV. The composition of the samples is gradually varied between pure nitride and pure carbide. The experimental reflectance data are analyzed by a Lorentz‐Drude model in order to determine both, the dependence of the interband absorption and of the free carrier concentration on the nitrogen to carbon ratio of the samples.
The Heat Capacity of LaNi2, LaNi5, PrNi2, and PrNi5 in the Temperature Range between 0.3 and 7 K
Authors: Sahling A. , Frach P. , Hegenbarth E.
Published: July 2007

Heat capacity measurements of LaNi2, LaNi5, PrNi2, and PrNi5 in the temperature range of 0.3 to 7 K are presented and discussed. For Pr compounds a Schottky contribution to the heat capacity is found and compared with the value computed from the crystal field level scheme determined by inelastic neutron scattering. Below 1 K, for PrNi2 a T−2‐term is observed, which is connected with the occurrence of a nuclear magnetic ordering below 0.25 K.
Photoemission Studies of Crystalline Arsenic
Authors: Raisin C. , Bertrand Y. , Robin J.
Published: July 2007

The electronic band structure of crystalline arsenic is studied by ultraviolet photoemission spectroscopy. Angle‐integrated photocurrent is measured using a retarding field method and energy distribution curves are thus obtained in the 7.5 to 27.4 eV range. The numerous structures seen on energy distribution curves are identified as high density‐of‐state peaks. These experimental results are fruitfully compared to the calculated valence band structure of As.
Energy of Anion Polarization in Layered Structures
Authors: Urusov V. S. , Dudnikova V. B.
Published: July 2007

In layered structures the anion position has low local symmetry. The result are induced anion dipoles which strongly interact with each other and with all the remaining crystalline matrix. Two different approaches are examined to take account of the anion polarization energy in layered structures. The lattice energy is calculated with regard to the anion polarization term for some halides of bivalent metals (Mg, Ca, Cd, Mn, Pb). The polarization correction to lattice energy is found to be large, 3 to 4 eV. Impurity dissolution energies are recalculated for those cases where the pure impurity component forms a layered structure: their values are found to be positive and correct in order of magnitude.
Low‐Temperature Conductivity and Mobility in Semiconductors
Authors: Gegechkori T. O. , Yakeli V. G. , Kachlishvili Z. S.
Published: July 2007

The influence of the free‐carrier concentration upon the low‐temperature conductivity is investigated. The variation may be due either to temperature effects (under thermal equilibrium conditions) or to the influence of an electric field (under non‐equilibrium conditions). The effect considered is significant up to the temperature at which the free‐carrier concentration saturates and for the thermal electrons at low compensation ratio. Then the low‐temperature conductivity considered as a function of the temperature and electric field strength acquires a sharp minimum while the maximum of the conductivity becomes higher and shifts towards lower temperatures and smaller fields. The comparison with experimental data shows quite a good agreement between the experimental and theoretical curves. This suggests that the mobility minimum which for rather a long time was being observed and not understood is due to the effects discussed above. The cascade electron capture cross‐section of the ionized donors is re‐calculated using the sticking probability corrected by Abakumov and Yassevich. The result is used to calculate the capture coefficient in a strong electric field.
Free Induction of E1'‐Centres in Crystalline Quartz
Authors: Fedoruk G. G. , Rutkovskii I. Z.
Published: July 2007

The results of an experimental investigation of the free induction of E‐centres in crystalline quartz are presented. The EPR technique based on the pulsed change of the polarizing magnetic field is used. The magnetic system being coherently excited is controlled by the transient oscillations of the absorption signal. It is shown that the transient oscillation and free induction features cannot be described by the Bloch model.
Study of Rearrangements of Intrinsic Defects at Annealing of Proton‐Irradiated Silicon
Authors: Kuznetsov V. I. , Lugakov P. F.
Published: July 2007

Rearrangement processes proceeding during annealing of electrically active radiation defects in heavily irradiated (30 MeV protons) Si when the concentration of primary defects induced exceeds the concentration of impurities available in crystal are studied. Czochralski grown and vacuum floating‐zone n‐ and p‐type silicon (ϱ = 3 to 500 Ω cm) are used. Experimental results obtained from the analysis of the Hall coefficient temperature dependences show that the rearrangement of intrinsic structural defects (diinterstitials and multivacancy complexes) occurs predominantly during annealing. Accumulation kinetics is studied and temperature stability range of some multivacancy complexes contributing to the forbidden gap energy levels Ev + 0.29 eV (400 to 650 °C), Ev + 0.32 eV (500 to 750 °C), Ev + 0.22 eV (500 to 700 °C), Ev + 0.15 eV (500 to 800 °C), Ev + + 0.10 eV (600 to 750 °C), Ec −0.24 eV (500 to 850 °C) most of which are acceptor levels is determined. The diinterstitial (Si‐B3) center being annealed in the temperature range 300 to 500 °C is supposed to be a multicharge defect and has deep acceptor ( Ec −0.40 eV) and donor ( Ev + 0.35 eV) levels.
Electronic Structure of 3d and 4d Impurities in Mo and Nb
Authors: Podloucky R. , Deutz J. , Zeller R. , Dederichs P. H.
Published: July 2007

Calculations are presented for the electronic structure of 3d and 4d‐ impurities in Mo and Nb. Using the density functional theory in the local spin density approximation of Barth and Hedin the electronic structure of the impurity is calculated by the KKR Green's function method. The impurity is described by a single perturbed muffin‐tin potential which is determined self‐consistently. In Nb and Mo 4d‐ impurities with the same excess valence ΔZ show very similar density of states. All 4d‐ impurities are unmagnetic. In Mo, of all 3d‐ impurities only Mn, Fe, and Co are magnetic. InNb, the formation of local moments of 3d‐ impurities is uncertain according to the present calculations. The occurrence of the local moments cannot be understood by the Friedel‐Anderson concept based on virtual bound states. Rather the simple “covalent model” of magnetism recently introduced by Williams et al. gives a reasonable description of the spin polarized densities of states.
Scattering of Surface Polaritons by the Order Parameter Fluctuations in the Vicinity of a Phase Transition Point
Authors: Ponath H.‐E. , Strizhevskii S. V.
Published: July 2007

The scattering theory of surface polaritons (SP) by polarization fluctuations with formation of bulk waves in media propagating from the interface is accounted. It is supposed that dielectric permeability of the contacting media is negative (without dissipation) on the scattering frequency. The theory is applied to SP scattering by Debye relaxation soft mode. The temperature dependence of scattering intensity is analysed. The angle and polarization characteristics of scattering are concretized for the cubic crystal case.
X‐Ray Spectroscopic Investigation and Calculation of the Energy Band Structure of Rare Earth Monophosphide and Monosulphide
Authors: Gusatinskii A. N. , Alperovich G. I. , Soldatov A. V.
Published: July 2007

A joint X‐ray spectroscopic investigation is made of rare earth (RE) monophosphides and monosulphides, crystallizing in the NaCl‐type lattice, and the band calculation of some of them. X‐ray emission K‐ and L‐bands of phosphorus in RE monophosphides are obtained, and also the K absorption edges, K‐ and L‐emission bands of sulphur in RE monosulphides. From the results of the band calculation the dispersion curves are constructed, the total and local partial density of states is determined and the dependence of forbidden band width in monophosphides from the RE atomic number is obtained. The energy structures of the valence electron bands of investigated classes of compounds are similar in their principal features. Differences observed near the top of the band, essential for determination of physical properties, are connected with the localization of d‐ and f‐states. The possibility of X‐ray spectroscopic investigation of interatomic and intraatomic hybridizations is discussed, including shells, preceeding the valence ones, the electronic states of which can noticeably participate in the chemical bond. The nature of chemical interaction in the compounds studied is far from pure ionic, but is more polar than in compounds with a diamond‐like lattice.
Hot‐Carrier Galvanomagnetic Effects in High Magnetic Fields
Authors: Khan F. A. , Bhattacharya D. P.
Published: July 2007

By using the Boltzmann transport equation the low‐temperature galvanomagnetic effects due to non‐equilibrium charge carriers in a covalent semiconductor are investigated in the presence of a high (non‐quantizing) magnetic field. The energy and momentum of the free carriers are assumed to be scattered, respectively, by deformation acoustic phonons and static imperfections in order to obtain the energy distributions among them at low temperatures. The galvanomagnetic coefficients are calculated for the weakly and also for the strongly heated charge carrier systems. The results may be used to yield information of the characteristics of different trapping centres and also to determine the dominant scattering mechanism of the free carriers.
Investigation of Transport Coefficients in Semimetals by the Variational Method. II. Bismuth
Authors: Gitsu D. V. , Golban I. M. , Kantser V. G.
Published: July 2007

A comparison of the experimental and calculated data for the transport coefficients in bismuth obtained on the basis of the variational microscopic model is carried out. The assumption about the predomination of carrier scattering on acoustic phonons in bismuth is confirmed. The values of deformation potential constants are calculated for a wide range of temperatures. The temperature and magnetic field dependences of transport coefficients in the wide range of temperatures and magnetic fields determined by variational method, completely reproduce the experimental data.
Ultrasound Modulation of γ‐Radiation in a Medium with Inhomogeneous Distribution of Mössbauer Nuclei
Authors: Mitin A. V.
Published: July 2007

Progress and applications of the theory of the inhomogeneous ultrasound modulation of γ‐radiation are treated. A new mathematical formalism of the theory is developed. In the self‐absorption case, an exact solution is given for a sample thin with respect to ultrasound absorption but thick with respect to γ‐ray resonance absorption. The possibility of observing “inner” ultrasound resonances of γ‐radiation on Mössbauer nuclei with hyperfine structure is shown. On the basis of the theory developed a method is suggested to determine the distribution of Mössbauer nuclei from γ‐ray resonance absorption data. Experiments dealing with the generation of ultrasound in ferromagnetic metals are compared with theory.
Integral Representation of the Incoherent Field in Disordered Materials III. Diffusion, Einstein Relation, and Landauer Formula
Authors: Lenk R.
Published: July 2007

The theory developed in Part I of this paper is applied to the diffusion problem, i.e. without driving forces in the medium. The diffusion coefficient is connected with the mobility determined previously by the Einstein relation. For one‐dimensional systems of finite length the transmission coefficient is calculated starting from the basic integral equation for the density. As expected, this coefficient is related to the mobility by the Landauer formula.
Theory of an Adiabatic Potential of Simple Metals. I. Exchange and Correlation Effects of Electrons
Authors: Zarochentsev E. V. , Teplov S. V.
Published: July 2007

A method of irreducible vertex functions for the description of many‐electron interaction is introduced allowing the exact evaluation of the electron—electron interaction in every series term of the perturbation theory in pseudopotential by which the electron part of the adiabatic potential is presented. The equations for fully many‐particle amplitudes are obtained. Fully many‐particle amplitudes are found assuming that the irreducible vertex functions depend only on the momenta q transfered to electrons scattered from the pseudopotential. Limiting values (with q → O) of irreducible vertex functions are derived using exact relations of the Fermi‐liquid theory.
Invariant Expansion of Energy of the Induced Magnetic Anisotropy
Authors: Volkov V. M. , Kustov E. F. , Maketov T. K. , Steczko G.
Published: July 2007

Using the reduction symmetry properties of crystals, the invariant expansions of the energy of induced magnetic anisotropy (IMA) are given for all point groups. The expansion is performed by deriving the tensor functions on the basis of polar and axial vectors. The relationship between the IMA invariant constants and the constants generally used is given. The influence of invariants of third order on IMA is discussed. The dependences of invariant constants on the composition are given for some magnetic materials.
Electron Structure and Optical Conductivity of NiTi
Authors: Boletskaya T. K. , Egorushkin B. E. , Fadin V. P.
Published: July 2007

The electronic energy spectrum, DOS, and optical conductivity of NiTi are calculated using the KKR method.
Tunnelling Model for Quasi‐One‐Dimensional Hydrogen‐Bonded Crystals
Authors: Plascak J. A. , Salinas S. R.
Published: July 2007

Tunnelling term is included in the Hamiltonian of an anisotropic Ising model which is used to explain the thermodynamic properties of quasi‐one‐dimensional hydrogen‐bonded ferroelectric crystals. A variational approach is used to treat the strong intrachain interactions accurately, while the weak interchain interactions are accounted for in a mean‐field approximation. Also, fittings are presented of some experimental data pertaining to crystals of PbHPO4.
Charge Transfers in Structurally Disordered Alloys
Authors: Weissmann Mariana , Cohan Norah V.
Published: July 2007

Structurally disordered binary alloys are investigated for which an atomic basis set is adequate. An iterative tight‐binding scheme within a non‐orthogonal basis and interactions among all pairs of atoms is used. The properties of the disordered systems are obtained as averages over several groups of a small number of random configurations of atoms. As the systems are structurally disordered a charge distribution is obtained for each type of atom and its average value is defined as the charge transfer. It is found that while the electrons are transferred to the atoms with higher ionization potential, as expected, they are also transferred to the larger atoms, and that both effects are almost additive. The results explain the charge transfers of several liquid alloys such as NaxK1–x AuxAg1–x, and the gold—alkali metal alloys.
Random Walk and Interaction of Vacancies with Imperfections in Diamond Lattice as a Discrete Markovian Process
Authors: Tishkovsky E. G.
Published: July 2007

The description of sites in diamond lattice in terms of elementary jumps is performed. The relations between the number of symmetrically arranged sites and the minimal value of elementary jumps needed to reach them from a given point are obtained. The physics of migration and interaction of vacancies with imperfections is represented by discret in space and time Markovian processes. Some characteristic features of Markovian chains and related physical processes are discussed.
Dynamics of Solitons in the Disordered Anharmonic Chain
Authors: Abdullaev F. Kh. , Abdumalikov A. A.
Published: July 2007

The dynamic behaviour of solitons in the random anharmonic chain in the long‐wavelength approximation is investigated. Long‐time accumulative effects are described of weak stochastic perturbations on Korteweg‐de Vries solitons. A law is found of the stochastic acceleration of solitons and the amplitude of a soliton is calculated in the case of short‐range fluctuations of the spatial inhomogeneities of the chain.
Low‐Temperature Lattice Specific Heat of CuAl
Authors: Bijalwan R. D. , Ram P. N.
Published: July 2007

The low‐temperature lattice specific heat of dilute copper—aluminium alloys are analysed on the basis of Grees function theory. An impurity model, which includes mass‐change at the impurity site and nearest neighbour central and noncentral force constant changes, is employed. The effect of volume change is also taken into account. The calculated results are in agreement with experimental measurements. Reduction in lattice specific heat is dominated by contribution from F1u irreducible representation. The calculated localized mode frequency on the basis of the defect model is in reasonable agreement with experimental value. The role of localized modes in understanding the change in lattice specific heat is discussed.
Self‐Interstitial in Hexagonal Close‐Packed Metals
Authors: Fendrik A. J. , Monti A. M. , Savino E. J.
Published: July 2007

Different symmetry configurations for an interstitial in a hexagonal close packed lattice are studied. Their stabilities are discussed and calculations are performed by means of an interatomic potential which reproduces some properties of Mg. The defect lattice eigenfrequencies and eigenvectors are calculated within the Einstein and a cluster approximation.