bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concentration dependence of the electron diffusion length in p‐type GaAs
Authors: Vigil E. , Diaz P. 
Published: January 2007

AbstractThe concentration dependence of the electron diffusion length in p‐type GaAs is analyzed based on experimental values reported in the literature and recent studies of minority carriers mobility in GaAs. The dependence of Ln with doping impurity concentration is determined for τnr ≫ τr and good agreement is found with highest reported experimental values of Ln; considerations are made about τnr. The dependence of electron mobility, diffusion constant, and radiative recombination lifetime on concentration are also given.
Asymmetry of isolated dislocation mobility in Silicon single crystals
Authors: Nikitenko V. I. , Farber B. Ya. , Yakimov E. B. 
Published: January 2007

AbstractThe main quantitative characteristics of asymmetry of isolated dislocation mobility in Si single crystals manifested in an essential difference (up to an order of magnitude) of the velocities of broadening and narrowing dislocation half‐loops have been investigated. Transition from broadening to narrowing of the dislocation half‐loop is found to result in the nonmonotonic temperature dependence of the 60° segments velocities as well as in changing the stress dependence of the velocity. The high temperature annealing of the sample befor the reversal of the dislocation glide is found to cause the asymmetry disappearance. The analysis of the results obtained is performed. It is concluded that the phenomenon observed may be due to a rearrangement of the point defect structure during the course of the dislocation glide.
Quantum effects in low temperature plastic deformation
Authors: Labusch R. 
Published: January 2007

AbstractA quantum mechanical calculation of the transition rate of a dislocation segment across an obstacle of finite width is performed. Compared with previous theories the achievement of the new treatment is that the finite compliance of the force distance profile is taken into account in the evaluation of the oscillatory modes. As a consequence, not only the DEBYEtemperature of the dislocation line but also the obstacle compliance enters the transition rate and determines the temperature regime in which quantum effects become observable. Furthermore, the results of classical thermal activation theory that is valid at high temperatures are for the first time derived from first principles.
Screw dislocation core structure and plastic deformation of BCC Metals
Authors: Kuramoto E. , Aono Y. , Tsutsumi T. 
Published: January 2007

AbstractThe core structure and an energy distribution around a screw dislocation core in model bcc lattice have been investigated in both unstressed and stressed states to clarify the controlling factors which determines the core type and the shape of PEIERLS potential. In the case of iron total four types of core structure were obtained, namely, unpolarized, polarized, split and high energy position and the shape of PEIERLS potential was so‐called camel hump type which gives a steadfast explanation for the presence of a hump on the yield stress — temperature curve of iron single crystal. The calculated results for the spatial distribution of the PEIERLS potential around a core show that the range of distribution is relatively small in the low PEIERLS stress case (iron), but is large in high PEIERLS stress case (vanadium).
Thermally activated deformation of Alpha Zirconium
Authors: Trojanová Z. , Lukáč P. 
Published: January 2007

AbstractThe effect of temperature on the yield stress of polycrystalline α‐zirconium has been examined at temperatures between 77 and 900 K. A strong temperature dependence of the yield stress (interrupted in the temperature ranges 300 to 400 K and 500 to 700 K where the yield stress is independent of temperature) indicates the occurence of the thermally activated processes during deformation. The activation volume at the onset of deformation has been determined as a function of temperature in the range 77 to 523 K.
On the morphology of <100>‐textured Germanium Crystallites in Zn—Ge Eutectic Alloy
Authors: Vetter JÖRg , Frühauf Joachim , Schneider Helmut GÜNther 
Published: January 2007

AbstractDifferent geometry parameters for the cross‐like germanium crystallites (eutectic dendrites) of the Zn‐Ge eutectic alloys unidirectionally solidified have been related to the growth rate R and liquid temperature gradient G using linear regression analysis. It has been found that for eutectic dendrite spacing λ, balk length d and balk thickness b follow the relationship of the type w = CwR−rwG−gw; Cw is a constant. The spacing relationship of eutectic dendrites (rλ = 0.21; gλ = 0.48) shows a similarity with published experimental and theoretical results on primary dendrite arm spacing (rλ = 0.25; gλ = 0.5). It has been shown in terms of a profile ration λ/d that for geometrical similar morphologies the relationship λ2R = const. is valid.
Pearson plot of chalcopyrite type (E11), phases
Authors: Paufler P. , Rotsch P. 
Published: January 2007

AbstractLinear equations are obtained from a hard sphere model that relate the unit cell dimensions of E11 compounds to the atomic diameters for coordination number 4. They are compared with experimental data for 36 compounds. So, the explicit identification of the atomic arrays that control the lattice parameters a and c can be performed.
Studies on syntactically coalesced Silicon Carbide polytype structures
Authors: Singh S. R. 
Published: January 2007

AbstractThe structure of two new silicon carbide polytypes, found in syntactic coalescence with a basic structure 6 H, have been worked out. The structure of polytype 21 H is [(33)263] and that of polytype 93R is [(33)434]3. The polytype 93R belongs to the structure series [(33)n34]3. One of the (00.1) growth face reveals the growth spiral. The splitting of diffraction spots indicates the existence of a high period polytype in the crystal. This high period polytype have been identified as 558H or 1674R. The growth mechanism have been discussed in the light of above observations.
Study relating to temperature stability of the Natural Laumontite Zeolite
Authors: Rykl D. , Pechar F. 
Published: January 2007

AbstractOn the basis of the DTA measurements, the natural laumontite zeolite has been subjected to thermal decomposition at temperatures of 20, 250, 420, 580, 750, and 1000°C. The decomposition products were identified by the X‐ray powder method (CuKα‐) and IR spectroscopy (Nujol). It has been determined that the crystal structure of laumontite is stable up to the temperatures of 250°C. The dehydration of the mineral that takes place has three phases. With the increasing temperature, besides the conserved laumontite basic lattice (up to 420°C), a new phase “X” (paraleumontite) is produced. At 1000°C the laumontite is transformed in anorthite. The following phenomena correspond to dehydration: The intensity decrease of the OH stretching vibration, vanishing of librations and H2O bending vibrations. The remaining water is hydrolytically split up and forms structural OH‐groups which partially outlast up to 1000°C.
Regularities of thermal deformations in Monoclinic Crystals
Authors: Filatov S. K. , Andrianova L. V. , Bubnova R. S. 
Published: January 2007

AbstractThe results of calculations of thermal deformation tensor and its analysis are given for eleven silicates and vanadates of clinopyroxenic structure. It is shown that the level of thermal deformation anisotropy in monoclinity plane is in stable correlation with velocity of monoclimity angle change. The correlation is explained by considerable contribution of shear component into deformations. Considering the shears it is possible to understand, to separate the thermal deformations in monoclinic crystals into components and to summarize them from those components. The given regularities permit generalisations for triclinic crystals as well as for pressure and chemical (compositional) deformations.
The structure of N‐Pyrid‐4‐yl‐iminotriphenylphosphorane, C23H19N2P
Authors: Kulpe S. , Seidel I. , Bödeker J. , Köckritz P. 
Published: January 2007

AbstractMr = 353.9, monoclinic, P 21/c, a = 11.248(2), b = 11.323(2), c = 14.845(4) Å, β = = 95.87(2)0, Z = 4, V = 1880.8(3) Å3, Dx = 1.28 Mgm−3, final R = 0.049 for 1995 independent reflections excluding those with |F0| < 5 σ(F0). Intensities were measured with an automatic diffractometer. The magnified imagePNC‐group of the molecule is nearly coplanar with the pyridine ring (dihedral angle 4.1°). The P atom and the C(2) atom of the pyridine ring overlap with their van der Waals spheres and have nearly the position with the maximum of steric hindrance. This conformation is the consequence of a conjugation between the Ph3PNgroup and the N‐standing pyridine ring as well as of an attraction between the P atom and the C(2) atom. A similar conformation has been observed in the molecule of N‐pyrid‐2‐yliminotriphenylphosphorane.
The structure of N‐Pyrid‐2‐yl‐iminotriphenylphosphorane, C23H19N2P
Authors: Kulpe S. , Seidel I. , Bödeker J. , Köckritz P. 
Published: January 2007

AbstractMr = 353.9, monoclinic, P 21/c, a = 11.371(4), b = 11.391(5), c = 14.699(11) Å, β = = 97.78(2)0, Z = 4, V = 1888.6(6) Å3, Dx = 1.28 Mgm−3, final R = 0.052 for 2360 independent reflections excluding those with |F0| < 5 σ(F0). Intensities were measured with an automatic diffractometer. The magnified imagePNC‐ part of the molecule is nearly coplanar with the pyridinring (torsion angle 6.4°). The P atom and the N(2) atom of the pyridinring overlap with their van der Waals spheres and have nearly the position with the maximum of steric hindrance.This conformation of the molecule is the consequence of a conjugation between the Ph3P=N‐group and the N‐standing pyridine ring as well as of an attraction between the P atom and the N(2) atom.
The structure of Tetraphenyl Imidodiphosphate, C24H21NO6P2
Authors: Kulpe S. , Seidel I. , Herrmann E. 
Published: January 2007

AbstractMr= 481.24, monoclinic, P 21/c,a= 12.009(3),b= 12.305(5),c= 18.993(7) Å, β = = 122.1(1)0,V= 2377.2(6) Å3,Dx= 1.349 Mgm−3,Z= 4. FinalR= 0.051 for 2690 independent reflections excluding those with |F0| < 4 σ(F0). Intensities were measured with an automatic diffractometer. The two phosphoryl oxygen atoms are in trans position. The acidic hydrogen atom is bonded at the nittogen atom. The molecules form dimers connected by NH … O intermolecular hydrogen bonds. Results are compared with those of the structure of tris(tetraphenylimidodiphosphato)ytterbium (III).
The molecular and crystal structure of the Steroidal Alkaloid Aculeamine
Authors: Kutschabsky L. , Pfeiffer D. , Coll F. , Adam G. 
Published: January 2007

AbstractA new solanocapsine‐type alkaloid named aculeamine has been isolated from roots of Solanum aculeatum and its structure has been established by X‐ray analysis as 22,26‐epimino‐23β‐methoxy‐16α,23‐epoxy‐5α,25αH,25βH‐chloestane‐3β‐ol. The compound crystallizes in the hexagonal space group P61 with the lattice parameters a = b = 16.706, c = 17.056 Å, α = β = 90°, γ = 120°. The final residual value was R = 0.079.
Vibrational properties of CdGa2S4
Authors: Neumann H. , Sobotta H. , Riede V. , Syrbu N. N. , Radautsan S. I. 
Published: January 2007

AbstractPolarization‐dependent infrared reflectivity spectra of CdGa2S4 are measured at 300 K in the wavenumber range from 180 to 500 cm−1. The analysis of the spectra yields three E and four B modes in this frequency range. The results are compared with previously published data and a final identification of the infrared active modes in CdGa2S4 is proposed. It is shown that the two‐phonon absorption spectra of CdGa2S4 can be interpreted in terms of zone‐centre two‐phonon combination modes. The relation between the lattice vibrational properties of chalcopyrite and defect‐chalcopyrite compounds is discussed.
Dielectric properties of vacuum deposited Samarium Oxide sandwich structures
Authors: Chandra Shekar M. , Subba Rao U. V. , Hari Babu V. 
Published: January 2007

AbstractSamarium oxide films were prepared by vacuum thermal evaporation using tantalum boats. The effect of aging, frequency and annealing on capacitance and tan δ were studied for AlSm2O3Al capacitor structures. The variation in capacitance with frequency at low frequency region is quite considerable. The existence of oxygen vacancies were confirmed from the thermoluminescence studies of these oxide films. The results were discussed on the basis of oxygen vacancies existing in these films.
The influence of elastic anisotropy on interaction of dislocations with point defects in BCC metals
Authors: Chernov V. M. , Ivanov V. V. 
Published: January 2007

AbstractWith the use of the anisotropic theory of elasticity the energies and the force‐distance profiles for the interaction of various types of straight dislocations with point defects of intrusion (atoms of N, C or O) and of replacement in BCC metals with a different degree of elastic anisotropy (Nb, V, Ta, α‐Fe) have been calculated. The calculated force‐distance profiles in most cases are not centrally symmetric, that leads up to a gliding asymmetry at the direct and reverse directions of dislocation motion. The crystal elastic anisotropy can change the relative mobility of dislocations of various types and accounts for a number of experimentally observed peculiarities of BCC metals stress‐strain properties.
Effects of the dislocation collective behaviour in plasticity of single crystals
Authors: Bengus V. Z. 
Published: January 2007

AbstractAn analysis has been carried out of the motion of a pair of sign‐similar edge dislocations under a constant shear stress in a simplest nonuniform field of internal stresses τi with a constant gradient. The influence is shown of the dislocation interaction and τi on the activation „volume”︁ of the average velocity of a dislocation pair, which is measured by the flow stress relaxation. The experimentally revealed anomalies of the activation „volume”︁ measured by the flow stress relaxation are regarded as corroborating the analysis and as manifestations of the collective effects of the elastic interaction of sign‐similar mobile dislocations.
Stationary creep and dislocation structure of Rhenium Single Crystals tested at moderate temperatures
Authors: Aristov V. V. , Myshlyaev M. M. , Romanov Y. U. A. , Shmytko I. M. 
Published: January 2007

AbstractCreep of rhenium single crystals is studied in tension along <11¯23> in the range of moderate temperatures (1233–1593 K). The kinetic equation is obtained to describe stationary creep rate as a function of temperature and stress, the parameters of this equation are determined. The activation energy is shown to be constant and independent of the stress applied. The X‐ray divergent beam technique (DB) is employed to show that glide occurs mainly in a basal plane, the preferential bending axis of its lattice lying along the tensile direction, and that the internal regions of the crystal comprise unstressed areas misoriented with respect to each other by an angle ≈ 10÷15'. The electron microscope studies of the dislocation structure suggest that hexagonal networks of dislocations located in basal glide planes are typical elements of the structural state.
Thermal effects in low‐temperature deformation: The response to strain rate changes
Authors: Kubin L. P. , Estrin Y. 
Published: January 2007

AbstractThe response of a deforming crystal to an abrupt strain rate change has been considered in the framework of the thermal model for low temperature anomalies of plastic deformation. Various modes of the deformation behaviour following strain rate changes have been predicted depending on the location of the point representing the state of the specimen in the plane of control parameters. A quantitive analysis of two characteristic modes of the deformation behaviour experimentally observed by KOMNIK and DEMIRSKI has been carried out with the aid of computer calculations and a good agreement with their data has been found.
Design of a continuous crystallizer by evaporation as unit operation
Authors: Chianese A. , Fasoli U. , Prati Gaglia M. P. 
Published: January 2007

AbstractWe have examined the continuous crystallization by evaporation as a unit operation, a process which is normally empirically designed and dimensioned. Through the mass balances and process equations (concerning the crystal growth, the secondary nucleation, the crystals dimensional and numeric balances) six equations were obtained upon which the calculation of the operating variables depends. The resulting mathematical system offers two degrees of freedom, and by defining the two independent variables it was possible to calculate — as shown in the graphics — the trends of the other six variables. One of the chosen independent variables was the diameter of the formed nuclei (as this is basically an experimental date), whereas the other was the variable τ which defines the residence time.
Morphology and characterization of ammonium bichromate crystals grown from aqueous solutions
Authors: Nowaczyk Z. , Sangwal K. 
Published: January 2007

AbstractThe morphology of ammonium bichromate single crystals grown from aqueous solutions by solvent evaporation method at temperatures between 22 and 56 °C is investigated. It is found that the crystal morphology changes monotonically with an increase in growth temperature. Chemical etching is used to characterize the as‐grown crystals.
Effect of stress field on spiral step patterns on n‐octacosane crystals
Authors: Prasad P. B. V. , Bhagavan Raju I. V. K. 
Published: January 2007

AbstractModifications in spiral step patterns on n‐octosane crystals resulting from stress fields is considered. Stress field seems to impede the propagation of growth fronts across it and leads to the formation of bunched step patterns. Effect of cylindrical stress fields with axes parallel and perpendicular to the direction of step motion is considered in altering the shapes of the bunched steps. Shear modulus of n‐octacosane crystals is estimated from the microtopographical features.
Kinetics of the gas bubble formation in liquids with chemical reactions under microgravitation. Open system
Authors: Cherepanova T. A. , Ushkans A. L. 
Published: January 2007

AbstractA method of description for the nucleation kinetics in multicomponent systems with chemical reactions is proposed. Approximated expressions for the steady state nucleation rate of the gas bubbles in liquid phase and the nuclei size distribution function by composition and size for open systems have been obtained. Description for the gravitation effect on the nucleation process is given.
Structure of N‐5‐Anilino‐pentadien‐(2,4)‐ylidenaniliniumperchlorate, C17H17N2O4Cl
Authors: Kulpe S. , Seidel I. 
Published: January 2007

AbstractMr=348.65, monoclinic, P21/n,a=11.088(2),b=17.521(3),c=8.845(2) Å, β=98.87(3)0,Z=4,V=1697.8(8) Å3,Dx=1.368(1) Mgm−3, μ(MoKα)=0.256 mm−1, λ(MoKα)=0.71069 Å,T=296 K. FinalR=0.040 for 2454 independent reflections excluding those with |F0|<4σ(|F0|). Intensities were measured with an automatic diffractometer. The structure belongs to the openchained cyanines. Characteristic for this class of compounds is their nearly ideal polymethinic electron structure with its main geometrical features: equalisation of bond lengths, alternation of bond angles, planarity of the polymethinic chain. All three features are significantly to be observed in the structure. The bond angle alternation determines essentially the shape of the molecules and the molecular packing.
Dislocation behaviour in annealed and aged LiF crystals
Authors: Ostapchuk E. I. 
Published: January 2007

AbstractParallel investigation of the magnitude of the critical strear stress τ0 and dynamic characteristics of individual screw dislocations at temperatures 4.2, 77, and 300 K has been carried out in LiF crystals after annealing and after long aging at room temperature. It has been established that in impure LiF crystals, even at such low temperatures as room temperature (0.25Tmelt), diffusion processes take place which lead to quantitative and qualitative changes of the structure of obstacles determining macroscopic and microscopic mechanical properties.
High amplitude dislocation damping in superconducting Pb and In
Authors: Lomakin V. V. , Pal‐Val L. N. , Ya. Platkov V. , Roshchupkin A. M. 
Published: January 2007

AbstractThe amplitude dependence of ultrasound absorption due to dislocations, α, has been studied for single crystals of pure lead and indium as well as for lead doped with Tl, Sn or Bi, both in the superconducting and normal state and for a wide range of ultrasound amplitudes, ε0. Pure and Tl‐doped superconducting lead at large ε0displayed a maximum on the α(ε0) dependence which became a plateau upon transition to the n‐state. This is direct evidence for a change from static to dynamic dislocation hysteresis as a result of the increase in the electron drag constant. Limit values for the dislocation loop lengths have been estimated, viz. 2.4 × 10−4cm <LN< 10.4 × 10−4cm. In other single crystals the dynamic hysteresis occurred both in the n‐ and s‐state. In all the single crystals, α increased with the increase of ε0above the maximum amplitude and onset of the plateau which was observed in both states. The effect is associated with non‐linear phenomena arising at significant loop flexures. The amplitude dependence of the losses due to this effect has been analysed, the results of the analysis being in good agreement with the experimental data.
Acoustic study of elastic properties, dislocation damping and plasticity of crystals
Authors: Kardashev B. K. , Lebedev A. B. , Nikanorov S. P. 
Published: January 2007

AbstractThe results of acoustic studies of elasticity and dislocation inelasticity of crystals are presented. Regularities of elastic anisotropy variation with ionicity of bonds in ANB8‐N crystals have been considered. Amplitude dependences of ultrasound damping supply the information on dislocation structure and dislocation — to point defect interaction. Oscillation of dislocations during internal friction measurements are compared to their translation motion at the onset of plastic flow.
Influence of magnetic flux trapping on softening effect during superconducting transition in alloys Pb‐Ni and Pb‐Sn
Authors: Abraimov V. V. , Kalugin M. M. , Soldatov V. P. 
Published: January 2007

AbstractThe value of the trapped magnetic flux in strained superconducting alloys Pb‐Ni and Pb‐Sn during n‐s transitions is measured and the correction is made of the obtained earlier on these alloys temperature and deformation dependences of the softening effect, stimulated by the superconducting transition. The peculiarities of the behaviour of the true softening effect on the mentioned dependences and physical nature of these peculiarities are discussed.
Investigations of the process of crystal growth from a liquid zone by Seebeck measurements
Authors: Rudolph P. , Gille P. , Genzel C. H. , Boeck T. 
Published: January 2007

AbstractAn arrangement for measuring the thermoelectric voltage (Seebeck signal) during the crystal growth from a liquid zone is described. Using the example of growing PbTe single crystals by THM it is shown that different equilibrium temperatures at both phase boundaries provide a differential Seekeck voltage depending on the crystal growth rate. Relaxation times which are needed to reach steady‐state conditions with respect to the concentration difference between the growing and solving interface in the case of a start or sudden stop of the heater motion can be obtained.