bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atomic Particle Ionization in a Crystal in Random Orientation
Authors: Bazylev V. A. , Demura A. V. 
Published: July 2007

AbstractA theory of the electron loss of an ion passing through a crystal in random orientation is developed for three mechanisms of ion–electron interaction with the crystal: 1) coherent atomic interaction with the crystal lattice without phonon production; 2) incoherent atomic interaction with crystal phonon energy changing; 3) electron–electron interaction with crystal electron energy changing. It is shown that under certain conditions any of the mechanisms considered can be dominant in the process of electron loss from the ion. It is also shown that for a multiply charged ion passing through the crystal an abnormal dependence of the ionization probability on the amount and direction of the ion velocity can occur.
The Mixing of Frenkel and Charge‐Transfer Excited States. II. Numerical Treatment of Non‐Symmetric Dimers
Authors: Schmid B. J. , Reineker P. 
Published: July 2007

AbstractThe mixing of Frenkel and charge‐transfer excitations is discussed for singlet excitions in a dimer consisting of inequivalent molecules. Depending on the parameter values of the system a more or less rapid crossover of the lowest eigenstate between a predominant Frenkel and a predominant charge‐transfer excitation is observed if one of the system parameters is varied. The case of singlet excitons in anthracene/TCNB is explicitly considered.
The Fundamental Absorption Edge Tail of Ferroelectric SbSI
Authors: Žičkus K. , Audzijonis A. , Batarunas J. , Šileika A. 
Published: July 2007

AbstractThe temperature dependence of the fundamental absorption edge of SbSI is studied in the range 320 to 5 K. In the paraelectric phase the edge is described by the Urbach's rule. The pertinent parameters of the ferroelectric phase are found to be temperature dependent. The influence of spontaneous polarisation on the absorption edge is discussed. The unusual Urbach behaviour in the ferroelectric phase is explained by the temperature dependence of the spontaneous polarisation. The results of SbSI absorption edge studies are found to be consistent with the microscopic model of Sumi‐Toyozawa.
Phase Transitions and Intervalley Jahn‐Teller Effect in the System (GeTe)1–x (AgSbTe2)x
Authors: Plachkova S. K. , Tersiev L. A. 
Published: July 2007

AbstractThe energy of intervalley Jahn‐Teller effect (IVJTE) accompanying the O–C phase transition in (GeTe)1–x(AgSbTe2)x solid solutions (x = 0.06) is calculated on the base of a band‐edge structure model of the group IV‐tellurides with T–L splitting in the rhombohedral phase. The heat effect of the transition is measured. It is shown that the contribution of the IVJTE energy in the whole energy balance of phase transition is ≈ 40%. This energy is used for the uniaxial deformation of a crystal.
Optical Determination of the Valence‐Band Parameters in CdTe
Authors: Milchberg G. , Saminadayar K. , Molva E. , Zelsmann H. R. 
Published: July 2007

AbstractThe set of valence‐band parameters μ, Δ, R0, introduced in the Baldereschi‐Lipari model allows the determination of several energy levels of shallow acceptors in a semiconductor. A critical examination of the methods of determining these parameters is presented. These values are calculated for CdTe using Lipari's analytical expressions for the electronic state energies and experimental data from luminescence and IR spectra of five acceptor impurities. The main conclusions are: 1) the restriction to transition energies (the only energies directly obtained from the experimental spectra) leads to more than one solution for μ, Δ, and R0; 2) when the energy levels of three “unperturbed” P states are known, the valence band‐parameters are unambiguously determined. For CdTe: μ = 0.69 ± 0.03, Δ = 0.12 ± 0.01, R0 = (30 ± 3) meV. Values of these parameters deduced directly from the experimental Luttinger parameters are generally too uncertain to be taken into account.
The Theory of X‐Ray Diffraction Analysis of Elastic‐Strain States in Epitaxial Films
Authors: Khapachev Yu. P. , Dyshekov A. A. , Kiselev D. S. 
Published: July 2007

AbstractThe possibility to determine five components of the strain tensor of an expitaxial film is demonstrated. The general expressions are given for the values of the discrepancy of periods of the film and the substrate, and for the components of the stress tensor in cubic heterostructures. Special emphasis is given to the definition of stresses in the layers of a superlattice.
XANES and EXAFS Study of the Compound CoAsSe
Authors: Chattopadhyay S. , Mande C. 
Published: July 2007

AbstractThe X‐ray absorption near edge fine structure (XANES) and the extended X‐ray absorption fine structure (EXAFS) associated with the CoK absorption discontinuity are investigated in the pure metal, in the compound CoAsSe and in two other similar trivalent compounds. The analysis of the results obtained enables to obtain the average bond length (Co‐ligand distance) in CoAsSe for which the value is not known from crystallographic work.
A Disorder Model of Melting II. Alkali Halides
Authors: Vaid B. A. , Sharma K. C. , Syal V. K. 
Published: July 2007

AbstractThe disorder model of melting recently proposed, is generalized to include alkali halides. The thermodynamic ‘defects’ are identified with the (ion‐)vacancy pairs existing in molten halides. The agreement of the calculated values of thermodynamic properties viz. thermal expansion coefficient, heat capacity, and compressibility, with the experimental data is found to be quite reasonable.
On Laser‐Induced Lattice Heating in a Polar Semiconductor
Authors: Vasconcellos A. R. , Luzzi R. 
Published: July 2007

AbstractNonlinear transport phenomena and relaxation processes in highly photoexcited polar direct‐gap semiconductors are considered. The rates of energy transfer between subsystems are calculated and it is shown that for ultra‐short laser pulses lattice heating is unimportant. However, for cw laser‐light illumination a pronounced enhancement of the lattice temperature is expected when laser power approaches, or surpasses, a critical value, leading the system to melting conditions.
Compressibility of Rare‐Gas Solids under the Effect of High Pressure
Authors: Narain J. , Agrawal G. G. , Shanker J. 
Published: July 2007

AbstractAn interionic potential model is formulated for rare‐gas solids by considering the effect of three‐body interactions, zero‐point energy, and thermal contributions. The model is applied to evaluate compression curves for Ne, Ar, Kr, and Xe, up to a pressure of about 20 kbar at their triple‐point temperatures. The calculated and experimental results are found in good agreement with each other.
Charge Transfer and Concentration Dependence of Magnetization in Amorphous FeB Alloys
Authors: Maksymowicz A. Z. , Stobiecki T. , Jarocki E. , Karaś W. 
Published: July 2007

AbstractMeasurements are reported of the magnetic moment μFe of Fe atoms in amorphous Fe1−xBx alloys. The observed concentration dependence of μFe can be explained qualitatively in terms of a simple rigid‐band model assuming a transfer of v electrons per B atom to the Fe d‐band. The rigid band is assumed as described by the density of states of densely packed structures. The best agreement is obtained for the charge transfer of about 1.5 electrons per boron atom yielding the observed critical concentration x = 0.60 at which magnetism disappears. Details of the density of states and the assumed number of electrons for pure Fe do not change the characteristic features of the μFe versus x dependence.
Free‐Carrier Optical Absorption Induced by Dislocation Scattering Mechanisms in III‐V Compounds
Authors: Vignaud D. , Farvacque J. L. 
Published: July 2007

AbstractThe influence of dislocations on the free carrier absorption in the case of III‐V compounds are determined theoretically taking into account the piezoelectric scattering potential associated with dislocations and the eventual existence of a deep flat band. Then the possibility to observe such effects is discussed and these calculations are illustrated by experimental results obtained on InSb.
Spectroscopic Study of the Crystal Field Splittings in TbPO4
Authors: Böhm W. , Kahle H. G. , Wüchner W. 
Published: July 2007

AbstractThe optical absorption and emission spectra of Tb3+ in TbPO4 in its tetragonal structure above 2.3 K are studied to obtain the energies, symmetry types, and wave functions of mainly the lowest crystal field components of the ground term 7F6. Crystal field parameters are evaluated and used to calculate the anisotropy of the single‐ion energy in a semi‐classical way. This gives interesting indications for the types of magnetic structures and Jahn‐Teller distortion which occur in this substance below 2.3 K.
On the Theory of Crystal Excitation by Electric Discharges
Authors: Voitikov S. V. , Gribkovskii V. P. 
Published: July 2007

AbstractThe problem is considered of semiconductor excitation by the streamer discharge electric field front in the case where the carrier generation processes do not reduce to the quasiclassical Zener tunneling because of high discharge velocities V and a steep front of the field. The streamerexcited interband transitions, unlike previously known ones, are shown to be indirect even in the first‐order processes taking place without phonon assistance. The first‐order transition slope is equal to h V. The calculated interband transition probabilities ωcv and the carrier concentrations Ne, Nh directly depend on the velocity of discharge, the form of its electric field, and the polarity: ωcv, Ne, and Nh are the greater, the higher the discharge velocity, the thinner the field front, and the faster the field intensity drop outside the discharge.
Electronic Theory of Atomic Short‐Range Order for Ternary Alloys Using the Pseudopotential Approximation and Its Comparison with Experiments
Authors: Mekhrabov Amdulla O. O. , Doyama M. 
Published: July 2007

AbstractAn analysis of the electronic theory of atomic short‐range ordering for ternary alloys in the pseudopotential approximation is made. The partial ordering energies and short‐range order parameters are calculated for ternary NiReMo, Ni3,(Fe0.10, Cr0.15), and Ni3(Fe0.20, Mn0.05) alloys using the model pseudopotential of Animalu. The comparison of the results between calculated and measured shows a good agreement for all the chosen systems.
Heat of Solution of Hydrogen in Aluminum
Authors: Mahajan S. , Prakash S. 
Published: July 2007

AbstractThe heat of solution of hydrogen in aluminum is investigated accounting for both, the lattice dilation and its relaxation. The lattice contribution is evaluated using a linearly screened local model potential for the ions. The non‐linear screening in the density functional formalism along with the exchange and correlation corrections in the jellium model is used to evaluate the proton contribution. The dilation enhances the lattice contribution by about 12% and decreases the protonic contribution by about 5%. The relaxation energy is reduced by about 40% for the dilated lattice. Adding all the contributions, the heat of solution is found to be 20% larger for the dilated lattice than that for the undilated lattice. The calculated heat of solution is found in good agreement with the experimental value. Comparing the results with the calculations of Perrot and Rasolt, the spherical solid model correction is estimated and it is found that it further improves the results.
The Photoexcited Flow of Nonequilibrium Phonons along a Crystal Surface
Authors: Blokh M. D. , Entin M. V. 
Published: July 2007

AbstractIt is shown, that for a light beam of oblique incidence to the crystal surface, a nonequilibrium phonon flux along the surface can exist. The transverse acoustic phonons of the lower branch of spectrum whose free path length is large at low temperatures give the main contribution to the flow. Such phonons arise either immediately at infrared absorption or as the result of the decay of optical and longitudinal acoustic phonons. The phonon energy flux is calculated and shown to be of the same order of magnitude as the incident light flux. The phonon‐electron drag current in the metal film bordering the unexposed surface of the dielectric is considered.
Angular Dependence of Spin‐Wave Resonance in Thin Films with Asymmetrical Boundary Conditions. Analytical Treatment
Authors: Jirsa M. , Kamberský V. 
Published: July 2007

AbstractThe boundary problem is solved for an isotropic homogeneous infinite insulator film with spins pinned asymmetrically by a uniaxial surface anisotropy. An arbitrarily oriented external magnetic field is assumed. Formally a simple condition for the values of the resonant wave‐vector k1 is obtained. The analytical expressions for the standing spin‐wave resonance (SSWR) mode linewidths and intensities are derived and discussed. The second part of the paper is devoted to the SSWR in thin metallic films with thicknesses 2d ≪ δ (the skin depth). The influence of conductivity on the mode positions, linewidths, and intensities is investigated analytically with the help of the spin‐wave approximation.
Temperature Dependence of the Electronic Energy Bands of NaNO2Crystal from 20 to 245 °C
Authors: El‐Dib A. M. , Hassan H. F. 
Published: July 2007

AbstractThe electronic band structure of NaNO2 crystals is calculated. The band structure is studied in the temperature range from 20 to 245 °C in the principal directions as well as at the high symmetry points inside the Brillouin zone. The temperature dependence of the minimum energy gap is also investigated. The calculations are carried out using a semiempirical LCAO method. The general features of the electronic energy bands at various temperatures are similar to that at 20 °C. The optical energy gap calculated at 20 °C equals to 3.24 eV which is in good agreement with experimental results.
Simulation fo Dynamical Bond Charge Transfer Properties in Elemental Semiconductors by Means of a Simple Quantum‐Mechanical Model
Authors: Pietsch U. 
Published: July 2007

AbstractA simple model is presented, that constructs the valence charge density of monoatomic semiconductors by linear superposition of appropriate diatomic molecules including the bond charges between next neighbour atoms. By means of this model the study of dynamical density properties is possible being in general calculated by full self‐consistent pseudopotential schemes. An essential feature of that density variation is the bond charge transfer, which will be analyzed with respect to the variation of the next neighbour distance and the bond angle. During stretching or compressing of the next neighbour distance the variation in the |s〉 portion of the valence orbitals has to be taken into account. Using the results for silicon, which are fitted to the self‐consistent outcome and to experimental data, an estimation of the transfer constants of other group‐IV elemental crystals is given. The model can be applied to the interpretation of dynamical bond charge transfer influenced experiments, like pressure and temperature dependence of the “forbidden” X‐ray reflection power.
Electrical Resistivity of Liquid Noble Metal Alloys
Authors: Alam M. A. , Tomak M. 
Published: July 2007

AbstractCalculations of the dependence of the electrical resistivity in liquid AgAu, CuAg, CuAu binary alloys on composition are reported. The structure of the binary alloy is described as a hard‐sphere system. A one‐parameter local pseudopotential, which incorporates s‐d hybridization effects phenomenologically, is employed in the resistivity calculation. A reasonable agreement with experimental trends is observed in cases where experimental information is available.
Derivation of Some Equations of State for Solids. A New Approach
Authors: Dass N. , Kumari M. 
Published: July 2007

AbstractIt is shown that the pressure‐independence of the product of the thermal coefficient of volume expansion, α, and the isothermal bulk modulus, BT, can give rise to the equation of state for solids as given by (i) Birch, (ii) Murnaghan, (iii) Tait, and others which are extensively used to fit the compression data. Moreover, some new equations of state are also developed. Further, as an example, the values of V(P, T)/V(0, T) are computed at 300 K for the case of sodium chloride and the results so obtained are compared with the data available in the literature. Overall, the conclusion is drawn that Murnaghan's equation of state is the best of all the equations of state available so far from the utility and practical point of view.
One‐Phonon Resonance Raman Scattering
Authors: Giner C. Trallero , Costa O. Sotolongo 
Published: July 2007

AbstractIndirect creation and annihilation probabilities for a Wannier‐Mott exciton with arbitrary kinetic energy and interacting with longitudinal optical (LO) phonons are obtained as a function of temperature. These results are applied to the calculation of the one‐phonon (Stokes and anti‐Stokes) resonance Raman scattering (RRS) cross‐section in the case when the intermediate states are considered to be hot excitons, interacting with the LO‐phonons. The scattering cross‐section of these processes in CdS at 77, 150, and 300 K are presented as a function of the incident radiation frequency. It is shown that the cross‐section calculated for high temperatures and for incident radiation energies larger than the energy gap is dominant with respect to the cross‐section corresponding to processes in which only one phonon participates (no indirect transition).
Photostimulated Transformations of Complex Colour Centres in Lithium Hydride Single Crystals
Authors: Pilipenko G. I. , Oparin D. V. , Tyutyunnik O. I. , Gavrilov F. F. 
Published: July 2007

AbstractOptical absorption, luminescence, and EPR are applied to study the nature of complex aggregate colour centres which arise in nonstoichiometric lithium hydride single crystals. Electron‐anionic disorder induced by the lack of hydrogen is found to create F‐centres which interact with the lattice through electron‐phonon coupling. Photostimulated transformation of F‐centres into F3‐centres is studied. The vibronic structure of the F‐centres absorption spectra is due to the interaction of the electronic transition with acoustic phonons TA(X), TA(L), LA(X), LA(X) + TA(X) and to the excitement of a quasilocal mode; the structure of F3‐centres spectra is due to the interaction of the electronic transition with acoustic TA(X), TA(L), LA(X), LA(X) + TA(W), and optical TO(L) phonons. The considerable deviation from the stoichiometry is shown to give rise to the formation of metallic lithium colloids.
On SCCF Theory of Falicov‐Ramirez‐Kimball Transitions in 1D Binary Alloys
Authors: Slechta J. 
Published: July 2007

AbstractSelf‐consistent continued‐fraction (SCCF) theory of the Falicov‐Ramirez‐Kimball (F‐R‐K) metalnonmetal transitions in 1D binary alloys, both with statistical short‐range order and purely random, is presented. Results for sets of critical parameters, and those of interest, are then given and shown that the F‐R‐K transitions depend, sensitively, upon the higher spatial correlations (HSC) in these alloys.
On the Possibility of Anomalous Bulk Photovoltaic Effect and of Induced Absorption in the Nominal Transparency Region of a Noncentrosymmetric Crystal in a Magnetic Field
Authors: Kristoffel N. 
Published: July 2007

AbstractThe possibility is shown of the appearance of photovoltaic current in the first order spectral transparency region for a noncentrosymmetric crystal in the magnetic field. This phenomenon must be accompanied by an unusual absorption induced by the electric field of the exciting light wave.
Cluster Structure of a Two‐Dimensional Lattice Gas Model
Authors: Esin V. O. , Danilyuk V. I. 
Published: July 2007

AbstractUsing the Monte Carlo method the cluster structure of a two‐dimensional lattice gas model is investigated. The ratios Γs and Γε of the perimeter S and boundary energy ε of a cluster to its size are studied over a wide temperature interval. For all temperatures, beyond some characteristic temperature‐dependent cluster size l0, ΓS and Γε are found to be independent of l. The temperature dependences of the ratios of the perimeter and energy of a cluster to its size, of the mean size of clusters, and of the vacant‐site concentration of occupied‐site clusters in a two‐dimensional system are studied.
Low‐Frequency Lattice Dynamics of NaNO2 Crystals
Authors: Kozlov G. V. , Kryukova E. B. , Wyncke B. , Brehat F. , Sherif M. E. 
Published: July 2007

AbstractSubmillimeter monochromatic BWT spectroscopy (3 to 33 cm−1) and far infrared reflection spectroscopy (40 to 600 cm−1) are used to investigate the low‐frequency dynamics of the classical ferroelectric NaNO2 of the order‐disorder type in the temperature interval 20 to 210 °C in the ferro‐ and paraelectric phase. In the submillimeter dielectric spectra ε★(v, T) of the NaNO2 crystal, together with the previously observed radiofrequency mode and the optical phonon 180 cm−1, low‐frequency anharmonic excitation subsidiary to the soft mode is recorded at the intermediate frequency 33 cm−1, Analysing the temperature behaviour of the parameters of this apparently relaxation excitation it is possible to assume that it is directly associated with the process of ferroactive crystal subsystem disordering at the ferroelectric phase transition.
Photo‐ and Thermochemical Reactions with Participation of Br− Centres in X‐Rayed KBr
Authors: Akilbekov A. , Dauletbekova A. , Elango A. 
Published: July 2007

AbstractThe photodissociation of Br centres (H′, V4, V2, D3 centres) at 4.2 K, created by X‐ray in pure and doped KBr at 4.2 to 300 K, and the thermorestoration of Br centres from their photodestruction products are investigated by the absorption method. It is shown that VF and H centres are created as a result of photodissociation of the high‐temperature Br centres (V4, V2, D3), but only H centres arise during the photodissociation of low‐temperature H′ centres. It is concluded that at temperatures above 80 K the Br ion occupies regular cation and anion sites, i.e. X‐radiation creates both cation and anion vacancies. At temperatures below 80 K the Br ion has an interstitial bent configuration, indicating that cation vacancies are not created.
On the Measurement of Solid State Compton Profiles by Inelastic Fast‐Ion‐Atom Collisions under Channeling Conditions. A Case Study
Authors: Bell F. 
Published: July 2007

AbstractSolid state Compton profiles can be obtained by inelastic ion‐atom scattering. The energy distribution of ejected electrons within the region of the binary encounter peak is connected with the Compton profile of the target atom. The question is discussed whether the core contribution to the total Compton profile can be suppressed under channeling conditions.
Theoretical Description of the Stopping Power of Light Ions in the Intermediate Energy Range
Authors: Kührt E. , Wedell R. , Semrad D. , Bauer P. 
Published: July 2007

AbstractA modified version of the binary encounter approximation by Kührt and Wedell is presented, where the motion of the target electrons is described in a more rigorous way. Moreover, the use of an alternative energy transfer cut‐off now makes it possible to describe the contribution of the outer electrons to the stopping cross section better. The very good agreement of this theory with experimental data is shown for a variety of target elements of different electronic structure (insulators, semiconductors, and metals).
Kinetic Properties of the Two‐Level Systems in Glasses with Account of Tunneling
Authors: Fushman D. A. 
Published: July 2007

AbstractThe kinetics of two‐level systems in glasses at low temperatures is studied with account of a distribution of their tunneling parameter values. Integral equations describing the process of spectral diffusion in a glass are obtained by the methods of the continuous time random walk theory. The long‐time asymptotics of the process is a superposition of individual and ‘collective’ relaxations, the latter one is characterized by the single relaxation rate. Manifestation of the results in echo saturation recovery experiments in glasses is discussed.