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61.
N. I. Kourov Yu. V. Knyazev A. V. Korolev V. G. Pushin Yu. A. Dorofeev 《Physics of the Solid State》2010,52(2):317-322
The effect of atomic disordering on the magnetic, electrical, and optical properties of the Pt74.1Fe25.9alloy close in composition to the stoichiometric Pt3Fe alloy has been studied. It has been shown that, as a result of severe plastic torsional deformation under high pressure,
the alloy transforms from the antiferromagnetic state (T
N=164 K) into the ferromagnetic state (T
C≈400 K). In this case, the residual electrical resistivity increases by a factor of more than two and the thermopower changes
its sign from positive to negative. The results of the studies of the optical conductivity agree with the previously calculated
electronic spectra of the atomically ordered and disordered Pt3Fe alloys in the range of interband transitions and with the obtained data on the electrical properties in the infrared range. 相似文献
62.
An experimental, temperature-dependent kinetic study of the gas-phase reaction of the hydroxyl radical with molecular bromine (reaction 1) has been performed by using a pulsed laser photolysis/pulsed-laser-induced fluorescence technique over a wide temperature range of 297-766 K, and at pressures between 6.68 and 40.29 kPa of helium. The experimental rate coefficients for reaction 1 demonstrate no correlation with pressure and exhibit a negative temperature dependence with a slight negative curvature in the Arrhenius plot. A nonlinear least-squares fit with two floating parameters of the temperature-dependent k(1)(T) data set using an equation of the form k(1)(T) = AT(n) yields the recommended expression k(1)(T) = (1.85 x 10(-9))T(-0.66) cm(3) molecule(-1) s(-1) for the temperature dependence of the reaction 1 rate coefficient. The potential energy surface (PES) of reaction 1 was investigated with use of quantum chemistry methods. The reaction proceeds through formation of a weakly bound OH...Br(2) complex and a PES saddle point with an energy below that of the reactants. Temperature dependence of the reaction rate coefficient was modeled by using the RRKM method on the basis of the calculated PES. 相似文献
63.
Oleg P. Korobeinichev Alexander A. Paletsky Tatyana A. Bolshova Vadim D. Knyazev 《Combustion Theory and Modelling》2013,17(5):927-939
The phenomenon of superadiabatic flame temperature (SAFT) was discovered and investigated in a low-pressure HN3/N2 flame using numerical modelling. A previously developed mechanism of chemical reactions in the HN3/N2 flame at the pressure 50 Torr and the initial temperature T0 = 296 K was revised. Rate constants of several important reactions involving HN3 (HN3 (+N2) = N2 + NH (+N2), R1; HN3 (+HN3) = N2 + NH (+HN3), R2; HN3 + H = N2 + NH2, R4; HN3 + N = N2 + NNH, R5; and HN3 + NH2 = NH3 + N3, R7) were calculated using quantum chemistry and reaction rate theories. Modified Arrhenius expressions for these reactions are provided for the 300–3500 K temperature range. Modelling of the flame structure and flame propagation velocity of the HN3/N2 flame at p = 50 Torr and T0 = 296 K was performed using the revised mechanism. The results demonstrate the presence of the SAFT phenomenon in the HN3/N2 flame. Analysis of the flame structure and the kinetic mechanism indicates that the cause of SAFT is in the kinetic mechanism: exothermic reactions of radicals with hydrogen atoms occur in the post flame zone, which results in the formation of super equilibrium H2 concentrations. The flame propagation velocity is largely determined by the second-order HN3 decomposition reaction and not by the reaction of HN3 with H, as was previously assumed. Calculation of the flame propagation velocity according to the Zeldovich-Frank-Kamenetsky theory with the decomposition reaction as a limiting stage yielded a value that agrees with that obtained in numerical modelling using the complete reaction mechanism. 相似文献
64.
Yu. V. Knyazev A. V. Lukoyanov Yu. I. Kuz’min A. G. Kuchin 《Physics of the Solid State》2013,55(11):2191-2195
The spectral properties of the intermetallic compounds NdNi5 ? x Cu x (x = 0, 1, 2) have been studied using optical ellipsometry in the wavelength range 0.22–16 μm. It has been established that substitution of copper atoms for nickel leads to noticeable changes in the optical absorption spectra, plasma frequencies, and relaxation frequencies of conduction electrons. Spin-polarized calculations of the electronic structure of these compounds have been performed in the local spin density approximation allowing for strong electron correlations (LSDA + U method) in the 4f shell of the rare-earth ion. The calculated electron densities of states have been used to interpret the experimental dispersion curves of optical conductivity in the interband light absorption region. 相似文献
65.
Yu. V. Knyazev N. B. Ivanova O. A. Bayukov N. V. Kazak L. N. Bezmaternykh A. D. Vasiliev 《Physics of the Solid State》2013,55(6):1175-1179
A concentration series of single crystals of iron-cobalt ludwigites Co3 ? x Fe x O2BO3 (x = 0.0125, 0.025, 0.050, 0.10, 1.0) has been synthesized. The structure has been studied using X-ray diffraction and Mössbauer effect. A preferred occupation of nonequivalent crystallographic positions by iron in the ludwigite structure has been revealed. It has been found that the valence of substituting iron ions is three. It has been revealed that the structure of the γ-resonance spectrum of Co2FeO2BO3 is complicated due to a composition disorder in the system. 相似文献
66.
G. A. Knyazev V. B. Voloshinov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(12):1643-1647
The optic, acoustic, and acousto-optic properties of tellurium single crystals are considered to analyze the possibilities of applying this material in acousto-optic filters to control mid- and far-IR radiation. The results of measuring the optic and acousto-optic parameters of a tellurium crystal are reported. The isotropic and anisotropic light diffraction by ultrasound in the crystal is investigated. The wide-aperture geometry of interaction in tellurium is implemented and an acousto-optic figure of merit M 2 of a tellurium crystal exceeding 10 × 10?15 s3 g?1 is experimentally obtained. 相似文献
67.
We report a detailed scaling analysis of resistivity rho(T,n) measured for several high-mobility 2D electron systems in the vicinity of the 2D metal-insulator transition. We analyzed the data using the two-parameter scaling approach and general scaling ideas. This enables us to determine the critical electron density, two critical indices, and temperature dependence for the separatrix in the self-consistent manner. In addition, we reconstruct the empirical scaling function describing a two-parameter surface which fits well the rho(T,n) data. 相似文献
68.
M. Maczka A. V. Knyazev N. Yu. Kuznetsova M. Ptak L. Macalik 《Journal of Raman spectroscopy : JRS》2011,42(3):529-533
Raman and infrared (IR) spectra of defect pyrochlores TaWO5.5, NH4SbWO6·H2O, HSbWO6·H2O, LiSbWO6·H2O, NaSbWO6·H2O, KSbWO6, RbSbWO6, CsSbWO6, and TlSbWO6 were measured. The obtained spectra are discussed using the factor group approach for the cubic Fd‐3m space group, and assignment of bands to respective motions of atoms is proposed. Our results show that the phonon properties of the pyrochlores are strongly affected by disorder, and therefore Raman and IR spectroscopies are very useful tools in studying disorder in this family of compounds. In particular, our studies have shown that in these ionic conductors disorder at sites occupied by NH , H+, or alkali‐metal ions decreases with increasing size and mass of these ions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
69.
V. A. Voitovich M. A. Davydova E. A. Zakharychev A. S. Knyazev A. A. Knyazev 《Polymer Science Series D》2018,11(2):183-185
The influence of glyoxal on the water resistance of pine–pine and beech–beech wood compounds formed by adhesives on the basis of polyvinyl acetate dispersion is studied. A noticeable increase in water resistance is observed for pine–pine compounds if the adhesive composite contains not only glyoxal, but also aluminum chloride and “chymol” additives. However, in the case of beech–beech compounds, the effect of this composition becomes less pronounced. 相似文献
70.
Knyazev Yu. V. Lukoyanov A. V. Kuz’min Yu. I. Vasundhara M. 《Physics of the Solid State》2019,61(6):969-972
Physics of the Solid State - The electronic structure and optical properties of a binary intermetallic FeSb2 compound are studied. The calculations of the band structure, that demonstrate the... 相似文献