bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Quasimolecular Approach to the Electronic Structure Calculations for Silver and Copper Halides
Authors: Ermoshkin A. N. , Evarestov R. A. , Kuchinskii S. A. , Zakharov V. K. 
Published: July 2007

AbstractThe quasimolecular large unit cell (QLUC) approach in the framework of complete neglect of differential overlap (CNDO) approximation is used for the one‐electron energy level and wave function calculations in symmetry points of the Brillouin zone of silver and copper halides AgX (X = F, Cl, Br), and CuX (X = Cl, Br). The parametrization scheme of the CNDO approximation is discussed. The results obtained are in agreement with the results of other band structure calculations and with the experimental data. The calculations of the impurity ion Cu+ in the silver site are also carried out in the framework of QLUC‐CNDO approach for AgCl and AgBr crystals. The impurity levels have t2g and eg symmetry and are situated near the top of the valence band. The centres of impurity bands, caused by the periodical distribution of defects in this model, are shown to converge with the increasing quasimolecule size to the energy levels of a single defect.
On the Elastic Constants of a Nematic Liquid Crystal
Authors: Schiele K. , Trimper S. 
Published: July 2007

AbstractComparing an extended form of the Landau‐de Gennes model for the order parameter with the free elastic energy for the director field of a nematic liquid crystal the temperature dependence of the Frank elastic constants is found. The theoretical results are in agreement with both the recent measurements and with molecular statistical theories.
Deuteron Dynamics in Crystal of Sodium Trideuterium Selenite
Authors: Fedotov A. P. , Shabanov V. F. 
Published: July 2007

AbstractA model of the deuteron dynamics in NaD3(SeO3)2 crystals without quantum mechanical tunneling is proposed. The possibility of deuteron jumps in hydrogen bond double‐minimum potentials is shown which is due to the deuteron‐deuteron interaction. The effect of the deuteron dynamics on the Raman spectrum is discussed. It is found that taking into account only dipole‐dipole interaction between the nearest neighbours is insufficient for the correct description of the deuteron dynamics and phase transition.
Critical Temperature of a Quasi‐One‐Dimensional Ising Model
Authors: Sokalski K. , Wójcik W. 
Published: July 2007

AbstractA quasi‐one‐dimensional Ising system containing n chains (n = 1, 2, 3) in an effective field is investigated. The dependence of the critical temperature on the coupling parameter with the effective field and on the number of chains in the system is shown.
Distribution of the Atoms on Grain Boundaries and in the Bravais Cell of the Coincidence Site Lattice
Authors: An Nguyen , Herrmann R. 
Published: July 2007

AbstractThe distribution of the atoms on symmetrical and asymmetrical coincidence grain boundaries in s.c., f.c.c., b.c.c., diamond, and zinc blende lattices is calculated. A general method is developed which allows to determine the number of atoms and the structure of the two‐dimensional lattice of any grain boundary plane and of the planes next to grain boundary.
The Impurity Effect on the Phase Transitions in Quasi‐One‐Dimensional Conductors
Authors: Seidel Ch. , Prigodin V. N. 
Published: July 2007

AbstractUsing bosonization and replica methods the influence of impurities on phase transitions in quasi‐1D systems is studied within the framework of the 1D Fermi gas model. The random impurity potential is taken as a white‐noise type. It is shown that nonmagnetic impurities suppress the dielectric transition but do not influence the superconducting state. Magnetic impurities suppress both the transitions, but the dielectric one considerably stronger than the superconductor one. Some special features occuring in the commensurate case are studied. Implications for organic 1D conductors are discussed.
A Relationship Between the Universal Law of Susceptibility Response and the Correlation Weakening Principle
Authors: Nigmatullin R. R. , Hill R. M. 
Published: July 2007

AbstractThe observation of the universal response of electrial, mechanical, acoustic, and magnetic systems in which power law behaviour in the time and frequency domains is seen indicates the universal behaviour of correlation functions in these systems. It is shown that this behaviour can be obtained by making use of the correlation weakening principle which plays an essential role in quantumstatistical physics and which does not depend on the detailed structure of the many‐body system involved.
Photothermal Creation of Cu°v Centres and Mobility of Anion Vacancies in X‐Irradiated KCl:Cu Crystals
Authors: Zazubovich S. , Usarov A. , Egemberdiev Zh. 
Published: July 2007

AbstractAssociates of Cu° atoms with anion vacancies v (Cu°vcentres) are used as luminescent detectors for the study of anion vacancy mobility in KCl crystals. It is found that near 220 K, Cu°v centres may be thermally formed because of the migration of v only to its neighbouring Cu° atom (i.e. the process occurs in {Cu°–v} pairs). An analogous process in {Cu+–v} pairs results in the creation of Cu+v centres. After Cu+v have trapped electrons released at the thermal destruction of Cu°, Cu°v centres are formed. {Cu+–v} and {Cu+–v} pairs are produced at low temperatures by the transfer of an F electron onto an impurity ion in irradiation‐generated {Cu+–F} and {Cu2+–F} pairs. If the crystal contains Cu centres, Cu°v centres may be formed at T > 370 K by the interaction of mobile VF centres, produced at a thermal dissociation of Cl3 molecular ions, with Cu centres. It is proposed that at T < 300 K it is not the isolated but the “associated” anion vacancy that can migrate. This process occurs in the field of some defects and needs a comparatively lower activation energy than the motion of isolated v. The isolated or “free” v which are believed to be mobile at higher temperatures, are practically absent in X‐irradiated crystals at T > 250 K due to the interaction of v with mobile cation vacancies or interstitial halide ions as well as due to the thermal association of v with neighbouring lattice defects.
Statistical Thermodynamic Approach to Some Hyperstoichiometric Dihydrides of Lanthanides (La, Ce, Pr, Nd, Sm) and Actinides (Np, Pu, Am)
Authors: Shohoji N. 
Published: July 2007

AbstractStatistical thermodynamics is applied to available equilibrium hydrogen pressure‐temperature‐composition relationships for cubic hyperstoichiometric dihydrides, MH2+x (O < x < 1, M = La, Ce, Pr, Nd, Sm; Np, Pu, Am). A statistical model is constructed based on a perfect face centred cubic lattice of metal atoms with fully occupied tetrahedral interstitial sites by hydrogen atoms and partly and randomly occupied octahedral interstitial sites by the rest of hydrogen atoms. Atomic partition function of hydrogen in MH2+x is found to be similar for all MH2+x. On the other hand, the atomic partition function of metals in MH2+x for different M is found to be different.
Band structure of TlGaSe2
Authors: Abdullaeva S. G. , Mamedov N. T. , Orudzhev G. S. 
Published: July 2007

AbstractA model of the TlGaSe2‐I band structure of the monoclinic modification is proposed. The monoclinic modification of TlGaSe2‐I is considered as a deformed tetragonal one. The band structure of the metastable tetragonal modification of TlGaSe2‐II is calculated by the pseudopotential method. The irreducible representations of the D184h group (TlGaSe2‐II) are expanded in irreducible representations of the C4s group (TlGaSe2‐I). It is found that the top of the valence band is located at the point Y (0,2π/bm, 0) of the TlGaSe2‐I Brillouin zone and is formed from band states N2, N4 of the tetragonal modification. The bottom of the conduction band is located at the point Γ of the TlGaSe4‐I Brillouin zone and is formed from T4 states. An additional extremum of the valence and conduction bands is located at the points Γ(A2) and Y(N6, N8), respectively. An interpretation of the absorption spectra of TlGaSe2‐I near the fundamental edge is proposed.
Ionic and electronic processes during frenkel defect annealing in KBr crystals above LHeT
Authors: Ziraps V. 
Published: July 2007

AbstractThe relaxation of radiation‐induced optical absorption spectra and a set of thermally stimulated curves (current, depolarization current, diffusion current, emission‐desorption of gas, thermal bleaching) of KBr crystals X‐irradiated at 4.6 K are recorded synchronously or step by step. A multistage annealing of defects is detected: (i) from 4.6 to 32 K about ten substages controlled by the I centre delocalization are accompanied by electron and energy release, (ii) from 32 to 60 K about six substages controlled by the H, centre delocalization are accompanied by corresponding electron and energy release and gas desorption peaks. A recombination of the migrating I or H centres within such complementary defect systems (pairs, triplets et al.) takes place: (i) {I…α}, {I… F… Vk}, {I… F'… Vk… Vk}, (ii) {H… F} and {H… F'… Vk}. Following phenomena in KBr at 4.6 K are observed and discussed: (i) the “F‐photostimulated” electron tunneling transfer within the excited pair {F* γ. HA} → (α… IA}, (ii) the effect of dc field (3kV/cm) caused Frenkel defect formation efficiency increase (by ≧ 10%), (iii) the photoelectrical dissociation of the α centres. Comments about the anion Frenkel primary defect generation mechanisms are made.
Lattice thermal conductivity of crystals with dislocations
Authors: Ansari M. A. , Kumar A. , Srivastava B. K. 
Published: July 2007

AbstractThe thermal conductivity of crystals containing dislocations is calculated using Kubo's relation. The correlation function is obtained using the projection operators as suggested by Wilson and Kim. It is observed that the phonon scattering by the strain field due to the dislocations is proportional to the phonon frequency and is anisotropic in nature.
Solitons in ferroelectric liquid crystal
Authors: Pires A. S. T. , Sá Barreto F. C. 
Published: July 2007

AbstractThe stable phases of liquid crystals whose constituents contain chiral molecules are studied. Starting from the Landau free energy for the order parameter the soliton‐lattice solution of the incommensurate phase is analysed in detail. The solutions of the normal and commensurate phases are obtained by the transfer matrix method.
Plasma reflection and hole optical effective mass in p‐HgTe
Authors: Ivanov‐Omskii V. I. , Sh. Mekhtiev A. , Rustambekova S. A. , Ukraintsev E. N. 
Published: July 2007

AbstractThe results of plasma reflection investigations in p‐HgTe are described. It is shown, that the plasma reflection spectrum shift towards small energies and the decrease of their depths with increasing temperature cannot be explained by the dielectric anomaly of the zero gap semiconductor due to the Γ8 → Γ8 transition only. The analysis of the experimental results shows that the optical effective mass value has both, a temperature and concentration dependence. Such a dependence may be explained in the frame of the Kane theory, if the renormalization of the energy spectrum of holes due to exchange electron—electron interaction is taken into account.
Two types of F centres in alkaline earth fluoro‐halides II. Double ENDOR experiments
Authors: Niklas J. R. , Bauer R. U. , Spaeth J.‐M. 
Published: July 2007

AbstractIn crystals containing simultaneously F(Cl−) and F(F−) centres in certain frequency regions the ENDOR spectra are superimposed to such a degree that an analysis is not possible. With double ENDOR experiments the ENDOR spectra of both centres can be separated. The ratio of the ENDOR signal heights compared to the double ENDOR signal heights is found to be characteristic for the shell of the nuclei involved. It can be used to discriminate between ENDOR lines of different shells. The effect cannot be understood on the basis of rate equations with reasonable assumptions for the spin—lattice relaxation times. It is probably due to spin diffusion.
K and L absorption spectra of aluminium from APW calculation
Authors: Ojala E. 
Published: July 2007

AbstractThe K and L X‐ray absorption spectra of Al are computed on the basis of an APW band structure calculation over an energy range of 40 eV. The results are compared with experiments. The overall shapes and especially the positions of the main maxima and minima of the experimental spectra are well reproduced by the theory. An appreciable lifetime broadening for the excited electrons is needed to smear out the structures to the extent found in the experiments. Discrepancies in the relative magnitudes of the spectral features between theory and experiment suggest that the core hole screening effect in the final state is primarily to scale the intensities in an energy dependent manner.
Elastic constants of the layered compounds Gas, GaSe, InSe, and their pressure dependence I. Experimental part
Authors: Gatulle M. , Fischer M. , Chevy A. 
Published: July 2007

AbstractThe elastic constants of the lamellar compounds Gas, GaSe, InSe are measured on several samples using an ultrasonic method, and the results are compared with previous publications. The variations of C33, C11, and C66 with an hydrostatic pressure are measured up to 3 kbars. In the range of pressure studied, the variations of these constants are perfectly linear. The results on the three compounds are very similar, and typical of the lamellar structure: an important variation of C33 caused by the weakness of the interlayer bond; on the other hand, C66 is very few affected by pressure.
Electronic structure of impurities in dilute alloys of Al
Authors: Mahajan S. , Prakash S. 
Published: July 2007

AbstractSelf‐consistent ”︁nonlinear screening calculations for point‐ion nonmagnetic impurities in jellium are made using the Hohenberg‐Kohn and Kohn‐Sham density functional formalism. The Friedel criterion is used to estimate the effective impurity valency and the Blatt correction is used for the size effect. The impurity induced charge densities in the Al matrix are calculated and an analytical expression, valid in both the preasymptotic and asymptotic regions is proposed. The net impurity effective charges are calculated and it is found that the matrix makes a substantial charge transfer in the impurity cell for all the alloys except AlMg and AlSn. The estimated residual resistivities agree fairly well with available experimental data.
Non‐linear optical susceptibilities of molecular crystals in the region of vibronic excitations. I. The three‐dimensional case
Authors: Lalov I. J. , Stoychev K. T. , Penchev S. P. 
Published: July 2007

AbstractThe quadratic non‐linear susceptibility in the single phonon vibronic spectra of molecular crystals is calculated (one Frenkel exciton + one non‐totally symmetric phonon). The following results are obtained: (a) the exciton—phonon interaction is decisive for the appearance of non‐linear susceptibility resonances in the vibronic region; (b) the two‐photon absorption spectrum is almost entirely of a one‐particle spectrum. The last result is experimentally confirmed elsewhere.
Effect of combined mechanical load and irradiation on hydrogen stabilization in LiF:OH
Authors: Akhvlediani Z. G. , Akhvlediani I. G. , Kalabegishvili T. L. 
Published: July 2007

Abstractγ‐irradiated LiF:OH crystals are investigated by the ESR and IR‐spectroscopic methods. The possibility of stabilization of atomic hydrogen in a cation vacancy is shown. It is established that applied mechanical load during the irradiation process does not affect the hydroxide decay, but has essential influence on the redistribution of the decay products (conditions are created for stabilization of hydrogen atoms in two different positions).
On the problem of an intermediate order in amorphous semiconductors
Authors: Iskra V. D. 
Published: July 2007

AbstractSimplest structural models are considered which take account of an intermediate order in both, homopolar and heteropolar, amorphous semiconductors. These models are used to study the influence of an intermediate order on the nature of an intrinsic random field in the material, hence, on the frequency dependence of the light absorption coefficient in the optical tail region.
Circular phonons and optical magnetization of crystals
Authors: Kiselev A. A. 
Published: July 2007

AbstractThe possibility of optical magnetization of crystals by excitation of circular optical vibrations is considered. An expression for the g‐factor of this sort of vibrations is derived for a crystal of rocksalt structure. Directions allowed for circular phonons in three‐dimensional lattices are studied, and the magnetization of an ionic crystal caused by circular resonance light wave is estimated using the classical approach and a point ion lattice model. A quantum approach to the problem is discussed, and creation and destruction operators for circular phonons are written.
Thermodynamic properties of uniform and dimerized hubbard chains
Authors: Lorenz B. 
Published: July 2007

AbstractThe thermodynamics of the uniform and dimerized half‐filled Hubbard chains is investigated within an approximation which takes into account the correlations in a given cluster of sites and which is valid for all model parameters and for all temperatures. The dependence of the specific heat on temperature changes from a one‐peak to a two‐peak structure with increasing interaction strength. The influence of dimerization is discussed. The local magnetic moment is found to decrease with increasing temperature in the high‐temperature region. It is suggested that this qualitative behaviour is more general and independent on dimension and band filling.
Determination of the charge carrier concentration and mobility in n‐gap by Raman spectroscopy
Authors: Irmer G. , Toporov V. V. , Bairamov B. H. , Monecke J. 
Published: July 2007

AbstractA method is presented which allows the determination of the charge carrier concentration and mobility in n‐GaP by Raman spectroscopy of coupled plasmon‐phonon modes. The results are compared with those of electrical measurements.
Optical properties of TiN single crystals
Authors: Köhler K. , Geserich H. P. , Wolf Th. , Müller‐Vogt G. 
Published: July 2007

AbstractThe spectral reflectance of TiN single crystals in the energy range between 0.5 and 6.2 eV is investigated. The crystals are grown by chemical vapour deposition. They have a very exact stoichiometric composition and a low content of impurities. The reflectance spectra are obtained on grown surfaces and analyzed by means of the Kramers‐Kronig dispersion relations as well as by fitting a Lorentz‐Drude model. It results that, in addition to the well‐known intraband and interband absorption, also direct transitions between the conduction subbands contribute to the optical absorption.
A binary magnetic alloy with competing exchange interactions and magnetic moments dependent on local environment
Authors: Zaborov A. V. , Medvedev M. V. 
Published: July 2007

AbstractMagnetic states of an alloy with competing nearest‐neighbour exchange interactions, IAA > 0, IAB > 0, IBB < 0, in which the magnetic moments depend on their local chemical environment in a step‐like manner (according to the Jaccarino‐Walker model), are studied in the vicinity of the transition temperatures from the paramagnetic states. It is shown that in the cases of s.c. and b.c.c. lattices the existence of the magnetic moment dependence on the local environment does not create any additional possibilities for the occurrence of the spin‐glass state in such alloys as compared to usual Heisenberg alloys with nearest‐neighbour competing exchange interactions of permanent magnetic moments.
Interaction of free hole intraband excitations with the A1‐phonon in highly doped (p‐type) tellurium
Authors: Goetz K. H. , Richter W. 
Published: July 2007

AbstractA remarkable asymmetry is observed in the Raman lineshape of the A1‐phonon of Te. This asymmetry increases with increasing hole concentration. The E‐symmetry phonons on the other hand always exhibit symmetric lineshapes. The A1‐phonon asymmetry is interpreted as a Fano‐type interaction between the A1‐phonon and a continuum of excitations. With the aid of various experiments this continuum is identified as intraband excitations of holes in the upper valence band.
Hyperfine magnetic field at 181Ta in YFe2
Authors: Akselrod Z. Z. , Budzynski M. , Komissarova B. A. , Kryukova L. N. , Ryasny G. K. , Sorokin A. A. 
Published: July 2007

AbstractThe hyperfine magnetic field at 181Ta in the ferromagnetic intermetallic Laves compound (Y0.97Hf0.03) Fe2 is measured by the perturbed angular correlation method. A value Hhf(Ta) = –14.4 T is obtained at 300 K. The temperature dependence of this field, measured in the range from 78 K up to and above, the Curie point, is shown to be different from that of the bulk magnetization.
Impurity potentials in diamond
Authors: Ortu≁o M. 
Published: July 2007

AbstractThe total screened potential produced by a static point‐charge impurity in diamond is calculated using a real‐space formalism. In this formalism a two‐flat‐band model is assumed. The potential is calculated for substitutional and “tetrahedral” and “hexagonal” interstitial positions. A very large cavity potential is obtained for interstitial impurities.
Chemical shift and EXAFS studies of some copper complexes
Authors: Bhattacharya P. , Chetal A. R. 
Published: July 2007

AbstractChemical shifts of the X‐ray K‐absorption edge of copper along with EXAFS are studied in the complexes CuC2O2(ammonia)2, Cu(LH)SO4 · 4 H2O, Cu(LH)2SO4 · 4 H2O, and Cu(phen) (xant)2. From the shift of the edge, it is concluded that the copper ion behaves as a cation in the complexes. It is also observed that as the partial charge on an absorbing ion increases, the chemical shift also increases. Bond lengths using Lytle et al.'s and Levy's methods are determined in the above complexes.
Macroscopical dielectric permittivities of nonhomogeneous media
Authors: Fokin A. G. 
Published: July 2007

AbstractBased on concepts of the functional analysis and treating the fields E and D as elements of the real vector Hilbert space H, a method is exploited for the calculation of macroscopical permittivities εM of nonhomogeneous media, and bounds within which they acquire their values. Series expansions are obtained for εM and γM = εM–1, and the convergence conditions are found for the series. Bounds are constructed for εM, which are contracting with the introduction of additional information on the medium used in the calculation. A comparison with the results of other authors is performed.
Polarized At Emission of In+ Centres in KI:In
Authors: Nagirnyi V. , Soovik T. , Zazubovich S. , Janson N. 
Published: July 2007

AbstractSpectral, polarization, and kinetic characteristics are investigated at 4.2 to 300 K for the blue luminescence of KI:In crystals with various In+ concentrations. It is established that the At emission band of In+ centres is elementary and its decay consists of only one component. The At emission is polarized only at excitation in the B and A absorption bands, the polarization degree is positive and grows as the energy of exciting photons decreases. The doublet structure of the At emission band as well as the second slower decay component which shows in KI:In with large In+ concentration a large negative polarization on excitation in the C band at 80 K, are caused by the presence, besides of In+, of some anisotropic indium centres in the crystal. Their emission is shifted by about 0.04 eV to lower energies with respect to the At emission of In+ centres.