共查询到20条相似文献,搜索用时 15 毫秒
1.
A number of crystal-forming polyhedral clusters X
n
Y
n
from which zeolite-like covalent crystals can be constructed and synthesized through copolymerization by faces are proposed.
A series of the smallest sized crystal-forming carbon clusters C2n
(where n = 10, 12, 14, 16, 18, 24, 36, 60) and silicon carbide clusters Si
n
C
n
(where n = 12, 16, 18, 24, 36, 60) are constructed. Their optimized geometries, electronic structures, charge transfers, band gaps,
cohesive energies, and electron density maps are calculated using the spinrestricted Hartree-Fock method in the 6–31G(d) basis set. The Si12C12 and Si24C24 clusters, referred to as the fulsicenes, are used to construct possible crystals with rock salt (Si12C12), simple cubic (Si24C24), body-centered cubic (Si12C12), face-centered cubic (Si24C24), and hyperdiamond (Si12C12) lattices, which are termed fulsicenites. Their X-ray diffraction patterns are calculated. 相似文献
2.
本文用包括平衡前发射在内的蒸发模型理论研究了(n,2n),(n,3n)反应的激发函数系统学.在对实验数据分析、拟合的基础上,得到一组较好的经验参数.利用这组参数计算得到的截面和实验结果符合较好. 相似文献
3.
S. S. Belyshev L. Z. Dzhilavyan A. N. Ermakov B. S. Ishkhanov V. V. Khankin A. S. Kurilik A. A. Kuznetsov V. I. Shvedunov K. A. Stopani 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(4):480-482
A race-track microtron is used to measure the yield of 18F in the reaction 19F(γ, n) at an energy of the electron beam of 55 MeV. 18F is widely used in positron emission tomography for high-sensitivity diagnostics. The currently available data are not sufficient to make accurate estimates of the yield of 18F in isotope production experiments using the reaction (γ, n). The value of σ?1 estimated in this work is (1.7 ± 0.1) mb. 相似文献
4.
5.
用量子化学的密度泛函理论方法对BX3(X=H,F,Cl)与烯烃CnH2n(n=2,3,4)形成的复合物进行了研究,结果表明,复合物的构型皆为BX3位于烯烃π键的上方,并且偏向氢原子数较多的碳原子一侧.C-C双键中的π电子通过向BH3中B的空p轨道转移电子而形成复合物,但BF3和BCl3与烯烃分子只是通过微弱的分子间作用力结合,复合物的形成使分子的振动光谱随作用的强弱而出现一定的红移现象. 相似文献
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7.
^132,134,136,137^Ba(n,p),^132,134^Ba(n,2n)反应截面测量 总被引:1,自引:0,他引:1
8.
J. L. Tallon R. G. Buckley M. R. Presland P. W. Gilberd I. W. M. Brown M. Bowden 《Phase Transitions》2013,86(4):171-190
The preparation, structure and properties of five members of the homologous series Bi2+x(Ca,Sr) n+1 Cu n O2n+4+δ are discussed, namely for n = 0, 1, 2, 3 and ∞. The two end members are insulating phases with a fixed oxygen stoichiometry but the members n = 1, 2 and 3 are superconducting phases with Tc depending on the calcium to strontium ratio and on oxygen stoichiometry as determined by annealing temperature and oxygen partial pressure. Maximum zero resistance Tc 's obtained are n = 1: 76 K, n = 2: 91 K and n = 3: 106 K. The effects of Pb-substitution in n = 2 and n = 3 are discussed with particular reference to the stabilisation of the latter phase. Rare-earth substitution is shown to raise Tc for n = 2 to at least 101 K without the introduction of the n = 3 phase. 相似文献
9.
S. R. Palvanov 《Physics of Atomic Nuclei》2014,77(1):35-38
The induced-activity method was used to measure the isomeric ratio of the yields of the (γ, n), (n, 2n), and (γ, 2n) reactions on the 113In nucleus. The energy dependence of the isomeric ratios of the yields of the photonuclear reactions 113In(γ, n)112m,g In and 113In(γ, 2n)111m,g In is studied in the energy range of 12–35 MeV. 相似文献
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11.
用活化法以^27Al(n,α)^24Na反应截面为中子注量标准,对14MeV能区中子引起的^93Nb(n,2n)^92mNb反应截面进行了测量。中子能量由硅探测器法测定。 相似文献
12.
在统计理论及考虑角动量守恒的激子模型的基础上,运用Monte Carlo方法计算(n,20)反应同质异能态截面比. 以59Co(n,2n)58Co、93Nb(n,2n)92Nb和181Ta(n,2n)180Ta的3个反应道为例,计算从其阈能到20MeV能区的同质异能态截面比,并和已有实验数据做了比较,结果符合较好. 这表明本文提供的方法是计算(n,2n)反应同质异能态截面比的一种有效方法. 相似文献
13.
14.
Li-Li Liu Shui-Xing Wu Xiu-Juan Jia Zhong-Min Su Rong-Shun Wang 《Molecular physics》2013,111(23-24):2511-2520
The molecular structures, electronic structures and absorption characters of–CH3,–C2H5,–CF3,–C2F5 substituted 5-(2-pyridyl) pyrazolate boron complexes were presented by density functional theory (DFT). The ground state structures of the title complexes were optimised at B3LYP/6-31G* level. In addition, a time dependent density functional theory (TD-DFT) method is applied to investigate the properties of absorption spectra and electronic transition mechanism which were based on the ground state geometries. The results show that the chemical bond formed between nitrogen in the pyridyl ring and boron can be attributed to coordination effect. The boron centre has a typical tetrahedral geometry with the adjacent atoms. The calculated absorption wavelengths for–CF3,–C2F5 substituted 5-(2-pyridyl) pyrazolate boron complexes are in good agreement with the experimental data. 相似文献
15.
利用硅团簇Si+n(n=1-3)注入Si单晶, 在Si单晶内形成一些单空位和双空位, 通过其光吸收谱观察到了带电状态为V02的双空位缺陷, 以及团簇效应对缺陷的影响, 正电子湮灭及TRIM程序模拟计算都表明团簇效应的存在. 相似文献
16.
17.
From isothermalM(H) curves nearT
c
, measured on polycrystalline Tl2Ba2Ca
n–1Cu
n
O2n
+4 and (Bi, Pb)2Sr2Ca
n–1Cu
n
O2n+4 (n=2,3) samples, we deduce the in-plane penetration depths ab as functions of temperature. An estimate according to the BCS weak-coupling clean-limit fit, which produces the data nearT
c
very well, yields ab(0)=3100 Å, 2320 Å 2210 Å, and 1960 Å for Bi2Sr2CaCu2O8, Bi1.6Pb0.4Sr2Ca2Cu3O10, Tl2Ba2CaCu2O8, and Tl2Ba2Ca2Cu3O10, respectively. A comparison between strong-coupling and weak coupling fitting curves clearly favours the weak-coupling temperature dependence of ab nearT
c
. 相似文献
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20.
V. V. Varlamov B. S. Ishkhanov V. N. Orlin N. N. Peskov M. E. Stepanov 《Physics of Atomic Nuclei》2013,76(11):1403-1414
Systematic discrepancies between the results of various experiments devoted to determining cross sections for total and partial photoneutron reactions are analyzed by using objective criteria of reliability of data in terms of the transitional photoneutron-multiplicity function F i = σ(γ, in)/σ(γ, xn), whose values for i = 1, 2, 3, ... cannot exceed by definition 1.00, 0.50, 0.33, ..., respectively. It was found that the majority of experimental data on the cross sections obtained for (γ, n), (γ, 2n), and (γ, 3n) reactions with the aid of methods of photoneutron multiplicity sorting do not meet objective criteria (in particular, F 2 > 0.50 for a vast body of data). New data on the cross sections for partial reactions on 181Ta and 208Pb nuclei were obtained within a new experimental-theoretical method that was proposed for the evaluation of cross sections for partial reactions and in which the experimental neutron yield cross section σ expt(γ, xn) = σ(γ, n) + 2σ(γ, 2n) + 3σ(γ, 3n) + ..., which is free from problems associated with determining neutron multiplicities, is used simultaneously with the functions F i theor calculated within a combined model of photonuclear reactions. 相似文献