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991.
采用量子化学自洽场方法及原子团簇理论对固氦晶格原子势能进行多体展开,定量确定了最近邻原子间距R在0.26—0.175nm之间,短程的两体到五体相互作用对晶体结合能及压缩特性的贡献,并对不同间距下多体展开式的截断位置进行了讨论. 结果表明:当最近邻原子间距R在0.26—0.175 nm之间取值,在具有hcp相结构的晶格中,氦原子势能的多体展开式是一收敛的交错型级数,该级数中两体项、四体项为正值,而三体项、五体项为负值. 当R在0.26—0.23 nm之间取值时, 仅保留级数中两体和三体项就能很好地描述晶格原子势能;当R在0.23—0.20 nm之间取值,多体展式需要展开到四体相互作用项;当R在0.20—0.175 nm之间取值必须再加入五体项贡献. 考虑到五体相互作用后,理论计算已能圆满地解释目前固氦等温压缩数据,其最大压力达 60GPa.
关键词:
固氦
状态方程
多体相互作用 相似文献
992.
Graded TiO2 films were deposited on unheated glass substrates by using a twin dc magnetron sputtering system. The graded TiO2 films showed a highly polycrystalline structure of anatase with a little rutile phases revealed by X-ray diffraction spectra. The surface energy of the fresh and UV irradiated films were evaluated by water contact angle measurement. The results indicated that the water contact angle of the fresh graded TiO2 films was found within 100-112°. The films then became a highly hydrophilic surface with the water contact angle of almost zero under 60 min UV irradiation. The XPS spectrum of Ti 2p revealed that the graded TiO2 films became a stoichiometric titanium oxide layer near the surface, proving that titanium was fully oxidized. It was found that the surface OH group density depended on the substrates employed for given sputtering conditions. In addition, AFM images revealed a considerably rough surface of the graded films with RMS roughness of 12.6-14.5 nm. One can conclude that the unique properties of highly hydrophobicity and photo-induced hydrophilicity can be attributed to fully oxidized chemical composition and higher roughness on the film surface. 相似文献
993.
994.
Günter Sigl 《Pramana》2003,60(2):279-289
The highest energy cosmic rays observed possess macroscopic energies and their origin is likely to be associated with the
most energetic processes in the universe. Their existence triggered a flurry of theoretical explanations ranging from conventional
shock acceleration to particle physics beyond the standard model (SM) and processes taking place at the earliest moments of
our universe. Furthermore, many new experimental activities promise a strong increase of statistics at the highest energies
and a combination with γ-ray and neutrino astrophysics will put strong constraints on these theoretical models. We give an
overview over this quickly evolving research field with focus on testing new particle physics. 相似文献
995.
The photodissociation spectroscopy of weakly bonded bimolecular complexes can give important insight into fundamental molecular interactions and dynamics. We have applied these techniques to a study of metal ion‐ethylene interactions in the Mg+(3s)‐C2H4 and Al+(3s2)‐C2H4 π‐bonded complexes. Experimental work is supported by ab‐initio electronic structure calculations. These experiments allow us to explore and compare the chemical binding, electronic structure, and nonadiabatic dissociation dynamics of these complexes. 相似文献
996.
T.P. Grozdanov E.A. Solov'ev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(1):13-22
The problem of determination of momentum distributions of ejected electrons in slow atomic collisions is studied within the
impact-parameter method by using a dynamic adiabatic basis which takes into account the correct boundary conditions. An expression
is obtained which relates the momentum distribution of the ejected electrons with a coherent sum of the delocalized dynamic
adiabatic eigenstates (elementary wavepackets). The form of the momentum distribution exactly coincides with the form of the total wavepacket in configuration space. General formulas are applied to a model problem of
electron detachment in the process in which the electron-atom interactions are described by the zero-range potentials. In the example considered, the momentum
distribution of ejected electrons, in the center-of-mass frame, exhibits a maximum located in the scattering plane on the
circle of radius (in atomic units), where v is the relative collision velocity and is the impact parameter.
Received: 5 October 1998 相似文献
997.
The title complex cis-bis(tetrahydrothiophene)-bis(nitrate) platinum(H), (tht)2Pt(NO3)2, was the reducing product from potassium hexachloroplatinate(IV) K2PtC16 where the platinum is tetra-valenced. Crystal data for CsH16N206PtS2: monoclinic, space group P21/c, a = 9.8833(5), b = 8.6744(4), c = 18.6407(9)A,β = 114.401(3)°, V = 1455.35(12)A3 Z = 4, Mr = 495.44, Dc = 2.261 g/cm3, F(000) = 944,μ = 9.950 mm-1, 2(MoKa) = 0.71073 A, T= 293(2) K, 2θmax = 54.96°, GOOF = 1.033, R = 0.0350 and wR = 0.0785 for 2572 observed reflections with I 〉 2σ(I). X-ray diffraction studies reveal that the title complex has interesting weak metal-metal interactions and two molecules linked by metal-metal interaction exist as a group. Luminescent spectrum illuminates red emission of the complex at room temperature. 相似文献
998.
Zeno Simon 《Angewandte Chemie (International ed. in English)》1974,13(11):719-727
Specific interactions or recognition processes are extremely important in many fields of chemistry and biology: typical examples are the enzyme-substrate and the antigen-antibody reactions. Quantitative predictions require a knowledge of steric fit, intermolecular forces, and molecular size. These considerations should facilitate design of new drugs. 相似文献
999.
The ultrasonic velocity and density measurements of lanthanum and cerium soaps in a mixture of 60 % benzene and 40 % methanol (v/v) were used to evaluate various acoustic and thermodynamic parameters and to determine the CMC. The results were interpreted in terms of soap-solvent interaction. 相似文献
1000.
R. J. Birgeneau R. A. Cowley G. Shirane H. Yoshizawa 《Journal of statistical physics》1984,34(5-6):817-848
Transition metal halides provide realizations of Ising,XY, and Heisenberg antiferromagnets in one, two, and three dimensions. The interactions, which are of short range, are generally well understood. By dilution with nonmagnetic species such as Zn++ or Mg++ one is able to prepare site-random alloys which correspond to random systems of particular interest in statistical mechanics. By mixing two magnetic ions such as Fe++ and Co++ one can produce magnetic crystals with competing interactions-either in the form of competing anisotropies or competing ferromagnetic and antiferromagnetic interactions. In this paper the results of a series of neutron scattering experiments on these systems carried out at Brookhaven over the past several years are briefly reviewed. First the critical behavior in Rb2Mn0.5Ni0.5F4 and FecZn1–cF2 which correspond to two-dimensional and three-dimensional random Ising systems, respectively, are discussed. Percolation phenomena have been studied in Rb2MncMgl–cF4, Rb2CocMgl–cF4, KMncZl-cF3, and MncZnl–cF2 which correspond to two-and three-dimensional Heisenberg and Ising models, respectively. In these casesc is chosen to be in the neighborhood of the nearest-neighbor percolation concentration. Application of a uniform field to the above systems generates a random staggered magnetic field; this has facilitated a systematic study of the random field problem. As we shall discuss in detail, a variety of novel, unexpected phenomena have been observed. 相似文献