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1.
研究M3C60(M=K,Rb)中C60分子的取向机制,利用点电荷模型和Lennard-Jones势考察了K^+-C60和C60-C60之间的相互作用对C60分子取向的影响。结果表明:M^+-C60之间的相互作用对C60分子的取向起决定作用,而使得C60分子的基态取向为两个标准取向之一。  相似文献   

2.
采用Recursion方法计算了C60分子的能态密度,所得的能隙、能级的简并度及顺序与LDA方法或者解析方法得到的结果吻合。  相似文献   

3.
利用吸收光谱和三阶微商吸收光谱,系统地分析了各种不同的非极性有机溶液中C60分子的吸收跃迁光谱结构,定量给出了不同溶剂对C60分子在紫外-可见区范围内各主要光学跃迁能量及HOMO-LUMO能隙的影响。根据C60分子能级结构参数随不同溶剂的变化特征,在线性近似下获得了孤立C60分子的本征电子能级参数和HOMO-LUMO能隙。  相似文献   

4.
巴基球C60内嵌原子(Li,Na,K,Rb,Cs;F,Cl,Br,I)的稳定存…   总被引:2,自引:0,他引:2  
本文用量子化学EHMO/ASED方法对巴基球C60内嵌原子(A=Li,Na,K,Rb,Cs;F,Cl,Br,I)进行了计算。结果表明除Li,Na外,其它元素当置于C60笼中心附近时,复合物能量最低,最稳定;对于内嵌Li,Na原子的巴基球(Li@60)及(Na@C60),当Li,Na位于围绕中心的一个球壳层(r-1.5A)内时最稳定。  相似文献   

5.
C60的发现,制备,结构,性质及其潜在应用前景   总被引:4,自引:0,他引:4  
冯孙齐 《物理》1992,12(6):333-341
C60是碳的一种新的同素异型结构.本文综述了C60的发现与制备方法,C60形成的机制与其绪构特征,以及C60的性质与其潜在的广阔应用前景.重点介绍用红外(IR)谱,13C核磁共振(NMR)谱和X射线衍射(XD)谱研究C60结构的结果,及掺杂C60固体的高温超导电性及其结构的最新研究进展.  相似文献   

6.
对C60克量级合成与制备获得成功以来的近七、八年间有关溶液中C60及其电荷转移配合物(CTC)吸光、发光特性研究做了详尽综述。化学特性的改善展示了C60及其CTC作为新型材料的潜在应用前景。  相似文献   

7.
测量了C60,C60/C70混合物分别在甲苯和1-甲基萘中的激发谱和荧光光谱,用532nm波长光为激发源.比较了纯C60及C60/C70混合物的荧光特性,对所观察到的发光谱进行了讨论.  相似文献   

8.
孙宇星  周锡煌 《物理学报》1995,44(6):873-876
描述了利用光吸收研究C60分子热力学性质的方法,通过对气态C60分子的研究,得到了气态C60分子从410至850℃的气压与温度的关系,同时给出在此温度范围同C60分子的热力学升华热为175kJ.mol^-1,并给出C60分子笼型结构的破坏温度为850℃。  相似文献   

9.
本文推导出正二十面体(I_h)对称的同系碳簇C_(60k ̄2)π-轨道的群约化通式;在紧束缚(Huckel)方案下,应用Lanczos三对用比方法,对每一类不可约表示仅需造出一个基函数作为起始态,便可使60k ̄2×60k ̄2久期方程达到理想的方块化,系统地求出了C_(60)—C_(2160)(k=1—6)按不可约表示分类的方块本证多项式和能级的解析形式(但五次以上代数方程只能求数值报)。文中叙述本方法的梗概,示范C_(60),C_(240)及C_(540)的计算结果。  相似文献   

10.
以Na2RbC60为例,在分析了现有模型的局限性后,考虑C60分子的取向,重新构造了碱金属离子与C60之间相互作用模型,并由此研究了碱金属离子在C60晶体中的平衡位置,确定了八面体位置的离子偏离中心,四面体位置的离子保留在中心.结果更符合实验事实.同时指出,由于取向有序,晶体内位于不同坐标的八面体间隙离子与四面体间隙离子体现出明显的两类. 关键词:  相似文献   

11.
采用密度泛函理论中的广义梯度近似(generalized gradient approximation,简称GGA),对M@C_(60)H_(60) (M=Li、Na)几何结构和电子性质进行计算研究.发现M原子的平衡位置处在偏心位置处,并且稳定的存在于一个围绕中心的球体内;掺杂能计算表明:M@C_(60)H_(60)需要在一定的实验条件下才能被合成出来;电子性质分析表明:M原子掺入到C_(60)H_(60)中,对费米能级附近有一定贡献,并产生了1 μB的净磁矩.  相似文献   

12.
本文用量子化学EHMO/ASED方法对巴基球C60内嵌原子(A=Li,Na,K,Rb,Cs;F,Cl,Br,I)进行了计算。结果表明除Li、Na外,其它元素当置于C60笼中心附近时,复合物能量最低,最稳定;对于内嵌Li、Na原子的巴基球(Li@C60)及(Na@C60),当Li、Na位于围绕中心的一个球壳层(r~1.5A)内时最稳定。  相似文献   

13.
Recent studies have shown that general‐base assisted catalysis is a viable mechanistic pathway for hydrolysis of smaller anhydrides. Therefore, it is the central purpose of the present work to compare and contrast the number of hydrogen atoms in‐flight and stationary in the transition state structure of the base‐catalyzed mechanisms of 2 hydrolytic reactions as well as determine if any solvent effects occur on the mechanisms. The present research focuses on the hydrolytic mechanisms of N,N‐dimethylformamide (DMF) and acetic anhydride in alkali media of varying deuterium oxide mole fractions. Acetic anhydride has been included in this study to enable comparisons with DMF hydrolysis. Comparative studies may give synergistic insight into the detailed structural features of the activated complexes for both systems. Hydrolysis reactions in varying deuterium oxide mole fractions were conducted in concentrations of 2.0M , 2.5M , and 3.0M for DMF and 0.10M for acetic anhydride at 25°C. Studies in varying deuterium mole fractions allow for proton inventory analysis, which sheds light on the number and types of hydrogen atoms involved in the activated complex. For these systems, this type of study can distinguish between direct nucleophilic attack of the hydroxide ion on the carbonyl center and general‐base catalysis by the hydroxide ion to facilitate a water molecule attacking the carbonyl center. The numerical data are used to discuss 3 possible mechanisms in the hydrolysis of DMF.  相似文献   

14.
Using B3LYP/6-31G* density functional level of theory, the structural and optical properties of the C60 and M@C59X cages have been investigated. Results indicate that the charge on C atoms and band gap of C60 cage are changed dramatically with the substitution of one B or N atom at one of the C sites and the Li and Na atom encapsulations in the C60 cage. The Mulliken analyses show that the charge is transferred completely between the alkali atoms and the C59X cage. The substitutional and encapsulation doping (SED) reduce the optical gaps of the C60 cage. Also, the oscillator strengths of the absorption peaks are dependent on dopant types.  相似文献   

15.
本工作利用热能碱金属原子与炽热W,Pt表面的相互作用,研究了碱金属原子与金属表面的电荷交换,以及金属表面吸附原子后表面功函数的变化。 关键词:  相似文献   

16.
A Mossbauer effect study has been done for Fe−C and Fe−M−C (M: Al, Mn) γ-iron. From the obtained fractional intensity of each component of spectra, the local interaction energies between carbon atoms were determined by means of Monte-Carlo simulation. The interaction energiees between carbon atoms and M atoms are also derived.  相似文献   

17.
Today, the design of new compounds with giant nonlinear optical responses is attracted to many researchers. Inspired by an interesting finding of a new class of heteroborospherenes which were formed by doping four carbon atoms in the B364- nanocluster (C4B32), we suggest the alkali metal-doped C4B32 (M@C4B32, M=Li, Na, and K) nanoclusters as high-performance nonlinear optical materials. Our results show that the alkali metal atoms have a considerable effect on the structural and electronic properties of the C4B32 nanocluster. We found that the doping alkali metal can remarkably decrease the HOMO-LUMO gap and significantly increases the first hyperpolarizability of the C4B32 nanocluster. Also, our results reveal that the first hyperpolarizability of the M@C4B32 nanoclusters can be progressively enhanced by increasing the atomic number of alkali metals. The effect of external electric fields on the nonlinear optical responses of the M@C4B32 has been systematically explored. We found that the first hyperpolarizability of the M@C4B32 compounds can be gradually increased by increasing the imposed external electric field from zero to the critical external electric field along the charge transfer direction (M→C4B32). Accordingly, this work presents an efficient strategy to improve the nonlinear optical responses of the heteroborospherenes.  相似文献   

18.
The energy loss spectra of 25-keV electrons after interaction with alkali halide vapors were measured. For the energy losses in the energy rangeE?6eV the positions of the peaks are consistent with light absorption measurements considering the energy resolution of the loss spectra. At higher energy peaks were observed, which correspond to the excitation of inner electrons belonging to the alkali atoms. From electron diffraction diagramms it follows, that for the lithium halides the concentration of dimers is considerable.  相似文献   

19.
We present Morse parameters for the interaction of graphene and silicene surfaces with the atoms of practically important metals Ni, Ag, and Li. The parameters' values are derived from the dispersion corrected density functional calculations. Two possible cases of sp2-hybridized C/Si atoms in the unbroken graphene/silicene sheets and sp-hybridized atoms near the vacancies are considered. Proposed Morse parameters' sets reproduce binding energies, bond lengths and oscillation frequencies of metal atoms adsorbed on the hollow positions over the rings of C60 and Si60 fullerenes. They also reproduce well the same quantities for the substituted C59M and Si59M fullerenes (M?=?Ni, Ag, Li).  相似文献   

20.
Using the density functional theory and the embedded cluster model, we have calculated the energetics of carbon-vacancy complexes in Fe as a function of distance separating the carbon atom(s) and the vacancy along different crystallographic directions. Carbon is found to prefer off-center sites from the vacancy and maintains a constant distance of approximately 3.35a 0 from the nearest Fe atom(s) independent of its direction from the vacancy center. This distance agrees closely with that in stoichiometric Fe3C. Our results suggest that the equilibrium site of carbon is one where it is coordinated to three Fe atoms in its nearest neighbor shell. Further decoration of vacancies by more than one carbon atom has been found to be energetically favorable. The binding of carbon to iron atoms is not caused by charge transfer between the atoms, but rather has a magnetic origin. Positron lifetimes at vacancies and vacancy-carbon complexes have also been calculated for various configurations. Our results are in general agreement with experiment.  相似文献   

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