Numerical calculation of the rate of strain of interstitial solid solutions under irradiation. I. Model of radiation creep

A model of radiation creep of interstitial solid solutions is developed on the basis of the combined motion of dislocations, including their glide and climb past obstacles. The obstacles considered are forest dislocations and pileups of radiation-induced point defects. A computational formula for the rate of strain is derived which describes creep at high stresses, when the gliding dislocations overcome some of the barriers by force, and a method is described for determining the average distance traversed by a dislocation in the glide plane under the influence of the stress until it is stopped by barriers. The results are compared with those of other authors. It is shown that the formula obtained for the rate of strain goes over in particular cases to those given by the previously known SIPA, Gittus-Mansur, and glide-climb models of radiation creep. Zh. Tekh. Fiz. 69, 64–71 (January 1999)     

On the influence of the electrical potential on the creep rate of aluminum

The influence of the electrical potential on the creep rate of aluminum is studied experimentally. The effect of the electrical potential applied to the sample is compared with the effect of the potential induced by the contact potential difference upon contact with seven different metals characterized by different work functions. It is revealed that these two types of electrical effects are qualitative equivalent to each other.     

Influence of interference effects on optical transitions with the participation of isoelectronic nitrogen impurities in GaAs1−yPy solid solutions

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 3, pp. 468–473, March, 1988.     

Formation of multilayer strained-layer heterostructures by liquid epitaxy. II. Simulation of the fabrication of heterostructures based on indium-arsenic-antimony-bismuth solid solutions

The formation of InAs_1−x−y Sb_xBi_y/InSb and InAs_1−x−y Sb_xBi_y/InSb_yBi_y strained-layer heterostructures by “capillary” LPE is simulated. The laws governing the dependence of the gap width E _g and the thickness d of the epilayers on the conditions of the process are revealed. It is shown that because of the sharp increase in the rate of epitaxial deposition as the LPE temperature is raised, the successful growth of epilayers of subcritical thickness is possible only up to T<550 K. The influence of the rate of laminar flow of the liquid in the growth channel in a relaxation regime and in a continuous pumping regime on the uniformity of the distribution of E _g and d in the epitaxial heterostructures is analyzed. Effective combinations of parameters for carrying out the process, which ensure the achievement of E _g ≈0.1 eV (77 K) in the active layers with variable-band-gap layers of minimal thickness, are established. Zh. Tekh. Fiz. 67, 50–56 (July 1997)     

Quantum microscopic vs. classical macroscopic calculations on the phenomenon of electrostatic influence

In order to compare microscopic and macroscopic approaches to the phenomenon of electrostatic influence, we have studied the atomic charges of an electric conductor, obtained either from macroscopic classical electrostatics, or microscopic quantum ab initio calculations. A torus was chosen as conducting material, built from valence monoelectronic atoms and influenced by an external point charge. The classical electric charges are obtained by integrating the macroscopic density over “atomic" sectors. This density is determined from a numerical integration of linearized electrostatic equations. The quantum charges are defined from Natural Orbitals in MP2/6-31G* calculations on clusters of different sizes. The overall agreement is good, with reasonable discrepancies due (i) to the continuity of the macroscopic model, which ignores the oscillations on atomic distances; and (ii) to the linearity constraint in the macroscopic equations.     

FLAPW-GGA calculations of the influence of Mn, Fe, and Co impurities on the electronic and magnetic properties of layered oxychalcogenides LaCuSO and LaCuSeO

The electronic and magnetic properties of oxychalcogenides LaCuSO and LaCuSeO with a layered ZrCuSiAs-type structure doped with impurity atoms M = Mn, Fe, and Co have been predicted using the first-principles FLAPW-GGA method. It has been shown that a partial substitution of 3d ^{n < 9} metal atoms for copper atoms in the structure of the initial matrix leads to the transition of the oxychalcogenides (nonmagnetic semiconductors) to the state of a magnetic half-metal with 100% spin polarization of near-Fermi electrons. In this case, the magnetic and conducting properties of the LaCu_{1 ? x} M _x S(Se)O systems are determined by the states of the [Cu₂(S,Se)₂] blocks with magnetic impurities separated by nonmagnetic semiconducting [La₂O₂] blocks.     

Thermal surface-tension coefficient of metals in polymolecular adsorption. Allowance for the difference in metals in the solid and liquid states

A brief survey is made of studies of the thermal coefficient of surface tension. It is shown that the coefficient should increase with the transition of a melt to the solid phase and with the adsorption of different substances on the surface of metals. The completed analysis indicates that the liquid phase has a greater adsorption capacity than the solid phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 59–63, October, 1985.     

通道宽度和初始流量对颗粒稀疏流-密集流转变临界开口的影响

通过实验研究斜面上二维颗粒流，当出口尺寸减小到临界值Dc时，发生稀疏流到密集流的突变.发现临界尺寸Dc与初始流量和通道宽度有关，通道宽度一定的情况下，临界开口尺寸Dc近似随初始流量Q0的平方根增大.在初始流量Q0一定时，临界开口尺寸Dc随通道宽度W近似线性增大.给出了这些关系的表达式，理论计算与实验观测结果一致.同时，也讨论了通道宽度影响临界开口尺寸的原因. 关键词： 颗粒物质 颗粒流     

Effect of stacking-fault energy on the development of a dislocation substructure,strain hardening,and plasticity of fcc solid solutions

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 35–46, March, 1991.     

Simulation of the influence of ultrasonic in-plane oscillations on dry friction accounting for stick and creep

We consider a pair of bodies contacting on an elastic substrate; the distance between the bodies oscillates harmonically at a high frequency. If a horizontal force is applied to the bodies, macroscopic movement starts only after achieving some critical value, which we identify with the static friction force of the oscillating system. The dependence of the static friction force on the oscillation amplitude is simulated numerically using the method of reduction of dimensionality. Results of simulation are compared with experimental data.     

The influence of substitutional imperfections on the electronic structure of refractory compounds. SP-element impurities in titanium nitride

Using the SCF MO LCAO (self-consistent MO LCAO method in the Mulliken-Wolfsbergelmholz approximation) cluster method and the Green's function method in the ASA-KKR (Korringa-Kohn-Rostoker method in the atomic spheres) approximation, the effect of substitutional impurities (O, C, B, Be, He) on the electronic structure of titanium nitride has been studied. The distributions of the local electronic states of impurity centers and the location of impurity levels in the total energy spectrum of the crystal have been calculated. A detailed discussion is presented of how the entire system of chemical bonding near a defect and the partial interatomic interactions vary as a function of the nature of the impurity atom. The results obtained are employed to interpret the available X-ray emission spectra of ternary systems, and also in treating problems of the mutual solubility of refractory binary phases and heterogeneous catalysis with their participation.A quantum chemical simulation of possible hydrogen atom positions in the nitride structure has been carried out. Hydrogen has been found to occupy preferentially tetrahedral interstices of the TiN lattice.     

Solution of the Ornstein-Zernike equation for a softcore Yukawa fluid. II. Numerical results

Numerical calculations are reported for the simplest case of the soft-core Yukawa fluid introduced in an earlier paper. Attention is given to the thermodynamic behavior, the correlation functions, and the interparticle potentials found by inverting the structural information using Percus-Yevick and hypernetted chain integration equation approximations.Supported by ARGC grant No. B7715646R.     

Investigation of multiple scattering contributions to the depolarization of light scattered by xenon and carbon dioxide in the critical region: II. Numerical calculations

With reference to the experimental data given in paper I of this series, we now present the results of numerical calculations on the depolarization factor in the critical region of fluids. Attenuation, Ornstein-Zernike effects and contributions from depolarized triple and polarized double scattering have been taken into account.     

Effect of magnetic field on the microplastic strain rate for C60 single crystals

Microplastic deformation in a magnetic field and in a zero field, as well as after preliminary action of a magnetic field on C₆₀ crystals, is studied with the help of a laser interferometer, which makes it possible to measure the strain rate on the basis of linear displacements of 0.15 µm. It is shown that the introduction of a sample into the field and its removal from a field of 0.2 T directly during sample deformation lead to a change in the strain rate, the decrease in the rate being accompanied by a brief interruption of deformation. The sign of the effect depends on temperature: the magnetic field accelerates deformation at room temperature and slows it down at 100 K. Preliminary holding of a sample in a field of 0.2 or 2 T produces a similar effect on the strain rate. Possible reasons for the observed manifestations of the magnetoplastic effect in C₆₀ and the relation between the sign of the effect and the phase transition at 260 K are considered.     

Investigation on the structural,electronic, elastic and mechanical properties of Ti2Al(C1-xOx) solid solutions: First-principles calculations

In the present work, the structural, electronic, elastic and mechanical properties of Ti₂AlC and Ti₂Al(C_1-xO_x) solid solutions were investigated using first-principles calculations for varied O content incorporation (x = 0, 0.125, 0.25, 0.375, 0.5). According to the calculation results, all Ti₂Al(C_1-xO_x) solid solutions with various x values are stable, and the bonding strength of the Ti–Al bond increases with the doping of O element. In addition, the shear modulus G and C₄₄ elastic constant of Ti₂Al(C_1-xO_x) solid solutions are both lower than the bulk modulus B, indicating that the phase has good damage tolerance. Not only that, compared with Ti₂AlC, the plasticity and toughness of Ti₂Al(C_1-xO_x) solid solutions are improved with the increase of O atom doping and doping ratio. Simultaneously, the doping of O atom is also beneficial to reduce the generalized stacking fault energy of Ti₂AlC, making the Ti₂Al(C_1-xO_x) solid solutions more prone to shear deformation, thereby further enhancing plasticity.     

Ionization of atomic hydrogen by electron impact. Numerical calculations for the “free-fall” atomic model

The atomic model of the zero-angular momentum electron trajectory was used in numerical classical three-body calculations of hydrogen atom ionization by electron impact. The results are compared with the results for microcanonical model and with experimental data.     

Ultrasound influence on the solubility of solid dispersions prepared for a poorly soluble drug

Solid dispersions have been successfully used to enhance the solubility of several poorly water soluble drugs. Solid dispersions are produced by melting hydrophilic carriers and mixing in the poorly water soluble drug. Supersaturation is obtained by quickly cooling the mixture until it solidifies, thereby entrapping the drug. The effects of using ultrasound to homogenize the molten carrier and drug mixture were studied. In particular, the increase in drug solubility for the resulting solid dispersions was analyzed. Piroxicam, which has very low water solubility, was used as a model drug. A full factorial design was used to analyze how sonication parameters affected the solubility and in vitro release of the drug. The results show that the use of ultrasound can significantly increase the solubility and dissolution rate of the piroxicam solid dispersion. Pure piroxicam presented a solubility of 13.3 μg/mL. A maximum fourfold increase in solubility, reaching 53.8 μg/mL, was observed for a solid dispersion sonicated at 19 kHz for 10 min and 475 W. The in vitro dissolution rate test showed the sonicated solid dispersion reached a maximum rate of 18%/min, a sixfold increase over the piroxicam rate of 2.9%/min. Further solid state characterization by thermal, X-ray diffraction and Fourier transform infrared analyses also showed that the sonication process, in the described conditions, did not adversely alter the drug or significantly change its polymorphic form. Ultrasound is therefore an interesting technique to homogenize drug/carrier mixtures with the objective of increasing the solubility of drugs with poor water solubility.