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First-principles investigation on the structural and elastic properties of cubic-Fe,TiAl under high pressures
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The structural, elastic, and thermodynamic properties of cubic-Fe2TiA1 under high temperatures and pressures are investigated by performing ab initio calculation and using the quasi-harmonic Debye model. Some ground state properties such as lattice constant, bulk modulus, pressure derivative of the bulk modulus, and elastic constants are in good agreement with the available experimental results and theoretical data. The thermodynamic properties of Fe2TiA1 such as thermal expansion coefficient, Debye temperature, and heat capacity in ranges of 0 K-1200 K and 0 GPa-250 GPa are also obtained. The calculation results indicate that the heat capacities at different pressures all increase with temperature increasing and are close to the Dulong-Petit limit at higher temperatures, Debye temperature decreases with temperature increasing, and increases with pressure rising. The cubic-FezTiA1 is stable mechanically under 250 GPa. Moreover, under lower pressure, thermal expansion coefficient rises rapidly with temperature increasing, and the increasing rate becomes slow at higher pressure. 相似文献
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YANG Jian-Hui LI Ping ZHANG Jian-Ping LI Hui-Li 《理论物理通讯》2008,50(8):468-472
Relativistic configuration interaction calculations for the states of 1s^22s^2, 1s^22s3l (l = s,p,d) and 1s^22p31 (l=s,p,d) configurations of iron are carried out using relativistic configuration interaction (RCI) and multi-configuration Dirac-Fock (MCDF) method in the active interaction approach. In the present calculation, a large-scale configuration expansion was used in describing the target states. These results are extensively compared with other available calculative and experimental and observed values, the corresponding present results are in good agreement with experimental and observed values, and some differences are found with other available calculative values. Because more relativistic effects are considered than before, the present results should be more accurate and reliable. 相似文献
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Jing-Kun Zhang Li-Cheng Song Ze-Min Zhang Rong-Gon Liu Zheng-Zhung Cheng Ji-Tao Wang 《Hyperfine Interactions》1988,40(1-4):363-366
The reaction of (u-RS)2 (XMgS) Fe2 (CO)2 with CpFe (CO)2I gave thirteen new compounds (u-RS) [CpFe (CO)2S] Fe2 (CO)4. Mossbauer spectra were obtained at 80K. Two quadrupote doubles (A set and B set) were present. The ratio of areas between A set and B set was close to 21. The molecule of every compound contained two Fe (2+) which were in the same chemical environment of low spin state with a coordination number of six, and the Mossbauer parameters of the two Fe (2+), IS=0.2–0.3 mm/s, QS=0.7–0.8 mm/s. In addition, the molecule contained a Fe (3+) in low spin state which was proved by ESR. Its Mossbauer parameters, IS=0.4–0.5 mm/s. QS=1.5±1.6 mm/s, The molecular structure of (u-MeS) [u-CpFe (CO)2S] Fe2 (CO)4 was determined by X-ray diffraction, monoclinic form, space group P21/n z=4, unit cell parameters, a=7.90A, b=10.77A, c=22.53A. 相似文献
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Magnetic iron oxide nanoparticles: Synthesis and surface coating techniques for biomedical applications
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Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite (Fe304) and maghemite (γ-Fe203), usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles (SPIONs) and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanopar- ticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests. 相似文献
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Hitoshi Osawa Toshiaki IwazumiHiroko Tokoro Shin-ichi OhkoshiKazuhito Hashimoto Hironobu ShojiEiju Hirai Tetsuya NakamuraSusumu Nanao Yasuhito Isozumi 《Solid State Communications》2003,125(5):237-241
The thermal phase transition of RbMnFe(CN)6 has been observed by Mn and Fe 3p-1s X-ray emission spectroscopy (XES) and 1s X-ray absorption spectroscopy (XAS). The thermal variations of the spin states and the valences of Mn and Fe were determined to be Mn2+(S=5/2)-NC-Fe3+(S=1/2) for the high-temperature (HT) phase and Mn3+(S=2)-NC-Fe2+(S=0) for the low-temperature (LT) phase. These transitions are thus caused by charge transfer between Mn and Fe. The temperature dependences of Mn and Fe 3p-1s XES and 1s XAS were observed as the composition of the spectra of the HT and LT phases. The ratios of the HT component in each spectrum show good agreement with the thermal transition curves observed with magnetic susceptibility measurements. 相似文献
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Electron stimulated desorption (ESD) experiments using a time-of-flight pulse counting method are reported for molecular CO chemisorbed on the Cr(110) surface at 90 K. Consistent with previous qualitative observations, negligible CO+ and O+ desorption signals were measured from the 1CO overlayer which saturates at 1/4 monolayer. For θCO > 0.25, a terminally-bonded (2CO) binding mode is populated in addition to the existing ∝1CO binding mode and the ion yield increases sharply. For 2CO, both O+ and CO+ ions are observed; the CO+ ions desorb with characteristically lower kinetic energies than O+ ions. Near saturation coverages of CO(ads), an observed decrease in the O+ yield is attributed to adsorbate-adsorbate interactions which reduce the ion desorption probability, as seen in ESD studies of terminally-bonded CO on other metals. These results are considered in the context of two possible models proposed for the 1CO binding state and related ESD observations for CO chemisorbed on Fe(001) and potassium-promoted Ru(001). 相似文献
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ZHANG Huan ;TIAN Bo ;ZHANG Hai-Qiang ;GENG Tao ;MENG Xiang-Hua ;LIU Wen-Jun ;CAI Ke-Jie 《理论物理通讯》2008,50(11):1169-1176
For describing various complex nonlinear phenomena in the realistic world, the higher-dimensional nonlinear evolution equations appear more attractive in many fields of physical and engineering sciences. In this paper, by virtue of the Hirota bilinear method and Riemann theta functions, the periodic wave solutions for the (2+1)-dimensional Boussinesq equation and (3+1)-dimensional Kadomtsev Petviashvili (KP) equation are obtained. Furthermore, it is shown that the known soliton solutions for the two equations can be reduced from the periodic wave solutions. 相似文献
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Two Darboux transformations of the (2+1)-dimensional Caudrey-Dodd-Gibbon-Kotera-Sawaka ( CDGKS) equation and (2+1)-dimensional modified Korteweg-de Vries (mKdV) equation are constructed through the Darboux matrix method, respectively. N-soliton solutions of these two equations are presented by applying the Darboux trans- formations N times. The right-going bright single-soliton solution and interactions of two and three-soliton overtaking collisions of the (2+1)-dimensional CDGKS equation are studied. By choosing different seed solutions, the right-going bright and left-going dark single-soliton solutions, the interactions of two and three-soliton overtaking collisions, and kink soliton solutions of the (2+1)-dimensional mKdV equation are investigated. The results can be used to illustrate the interactions of water waves in shallow water. 相似文献
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In this paper, by using the symmetry method, the relationships between new explicit solutions and old ones of the (2+1)-dimensional Kaup-Kupershmidt (KK) equation are presented. We successfully obtain more general exact travelling wave solutions for (2+ 1)-dimensional KK equation by the symmetry method and the (G1/G)-expansion method. Consequently, we find some new solutions of (2+1)-dimensional KK equation, including similarity solutions, solitary wave solutions, and periodic solutions. 相似文献
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New periodic wave solutions,localized excitations and their interaction for (2+l)-dimensional Burgers equation
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Based on the B/icklund method and the multilinear variable separation approach (MLVSA), this paper finds a general solution including two arbitrary functions for the (2+1)-dimensional Burgers equations. Then a class of new doubly periodic wave solutions for (2+l)-dimensional Burgers equations is obtained by introducing appropriate Jacobi elliptic functions, Weierstrass elliptic functions and their combination in the general solutions (which contains two arbitrary functions). Two types of limit cases are considered. Firstly, taking one of the moduli to be unity and the other zero, it obtains particular wave (called semi-localized) patterns, which is periodic in one direction, but localized in the other direction. Secondly, if both moduli are tending to 1 as a limit, it derives some novel localized excitations (two-dromion solution). 相似文献
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We study the Painlevé property of the (1+1)-dimensional equations arising from the symmetry reduction for the (2+1)- dimensional ones. Firstly, we derive the similarity reduction of the (2+1)-dimensional potential Calogero-Bogoyavlenskii- Schiff (CBS) equation and Konopelchenko-Dubrovsky (KD) equations with the optimal system of the admitted one-dimensional subalgebras. Secondly, by analyzing the reduced CBS, KD, and Burgers equations with Painlevé test, re-spectively, we find both the Painlevé integrability, and the number and location of resonance points are invariant, if the similarity variables include all of the independent variables. 相似文献
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A modified direct method is developed to find finite symmetry groups of nonlinear mathematical physics systems. Applying the modified direct method to the well-known (2+1)-dimensional B KP equation we get its symmetry. Furthermore, the exact solutions of (2+1)-dimensional BKP equation are obtained through symmetry analysis. 相似文献
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The double Wronskian solutions whose entries satisfy matrix equation for a (2+1)-dimensional breaking soliton equation ((2+ 1)DBSE) associated with the ZS-AKNS hierarchy are derived through the Wronskian technique. Rational and periodic solutions for (2+1)DBSE are obtained by taking special eases in general double Wronskian solutions. 相似文献
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Variable Separation for (1 + 1)-Dimensional Nonlinear Evolution Equations with Mixed Partial Derivatives 总被引:1,自引:0,他引:1
We present basic theory of variable separation for (1 + 1)-dimensional nonlinear evolution equations with mixed partial derivatives. As an application, we classify equations uxt = A(u, ux)uxxx + B(u, ux) that admits derivativedependent functional separable solutions (DDFSSs) and illustrate how to construct those DDFSSs with some examples. 相似文献
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Based on the Pfaffian derivative formulae, a Grammian determinant solution for a (3+1)-dimensional soliton equation is obtained. Moreover, the Pfaffianization procedure is applied for the equation to generate a new coupled system. At last, a Gram-type Pfaffian solution to the new coupled system is given. 相似文献
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CAO Ce-Wen YANG Xiao 《理论物理通讯》2008,49(1):31-36
Special solution of the (2+1)-dimensional Sawada Kotera equation is decomposed into three (0+1)- dimensional Bargmann flows. They are straightened out on the Jacobi variety of the associated hyperelliptic curve. Explicit algebraic-geometric solution is obtained on the basis of a deeper understanding of the KdV hierarchy. 相似文献
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By truncating the Painleve expansion at the constant level term, the Hirota bilinear form is obtained for a (3+1)-dimensional variable-coefficient Kadomtsev Petviashvili equation. Based on its bilinear form, solitary-wave solutions are constructed via the ε-expansion method and the corresponding graphical analysis is given. Furthermore, the exact solution in the Wronskian form is presented and proved by direct substitution into the bilinear equation. 相似文献
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Pd and Fe exchanged NaX and NaZSM-5 catalysts (Pd/Fe=5) were studied. The components formed in the course of hydrogen activation
at 720 K and their transformations taking place during treatments in CO+H2 at 570 and 500 K are described. PdxFe, Fe2+ ions in octahedral and tetrahedral environments and x-iron carbide components are identified. The bimetallic component is
not affected by the CO+H2 treatment. The Fe2+ ions located only in tetrahedral environment were transformed into iron carbide in the X zeolite framework, while the Fe2+ ions of octahedral environment were also transformed in part to carbide in the ZSM-5 lattice. 相似文献