富勒烯和碳纳米管稳定性与形成机理的图形理论定性研究

应用图形理论对不同种类碳簇体系的Kekulé结构数进行了计算, 并在半经验方法(AM1)和密度泛函理论(DFT)水平上，讨论了不同种类碳簇的结构与稳定性. 基于Kekulé结构计数, C-Cσ键数, 富勒烯的表面曲率和能量, 对石墨碎片的卷曲行为以及富勒烯的形成机理进行了讨论. 研究结果表明石墨碎片的卷曲, 一端闭合, 到完全封闭, 可以减少结构中的悬键; 随着新的C-Cσ键生成, Kekulé结构数将急剧地增加, 特别是大的富勒烯和碳纳米管, 这种增加更为显著. 大量Kekulé结构间的共振使体系获得显著的共振稳定化能, 稳定具有张力的富勒烯和碳纳米管, 并驱动平面碳簇结构向闭合结构的转化. 对于Kekulé结构数相近的碳笼, 表面曲率对曲面结构的稳定性有重要的影响. 把Kekulé结构计数和表面曲率结合起来, 可以合理地理解球形笼状富勒烯、闭合纳米管和类“洋葱”型结构等高碳簇在热力学上的稳定性.     

η2-C70[RhCl(CO)(PPh3)2]n配合物的合成和表征

从１９８５年Ｋroto等^[1]发现Ｃ６０等富烯至１９９６年富勒烯发现者获诺贝尔化学奖期间,在化学、物理、材料等领域掀起了富勒烯研究热潮^[2~8],此后,化学工作者致力于富勒烯的化学修饰,探索富勒烯各类衍生物的结构与性能之间的依赖关系,并在此基础上合成出具有独特结构与笥能的富勒烯衍生物,以期望在富勒烯及其衍生物的开发利用方面取得突破性进展。     

卤化富勒烯研究进展

自从C60被发现并能被大量制备以来,富勒烯化学已成为有机化学学科发展最快的领域之一。富勒烯通过多加成反应形成具有独特结构和性能的富勒烯卤化物和全氟烷基化物,为设计合成新型富勒烯基功能材料开辟了新方向。本文综述了近几年来在卤化富勒烯和全氟烷基化富勒烯的合成方法、结构及性能方面取得的最新进展,重点介绍了氟化富勒烯及其衍生化反应,并展望了该领域今后的发展趋势。     

卤化富勒烯研究进展

自从C60被发现并能被大量制备以来,富勒烯化学已成为有机化学学科发展最快的领域之一.富勒烯通过多加成反应形成具有独特结构和性能的富勒烯卤化物和全氟烷基化物,为设计合成新型富勒烯基功能材料开辟了新方向.本文综述了近几年来在卤化富勒烯和全氟烷基化富勒烯的合成方法、结构及性能方面取得的最新进展,重点介绍了氟化富勒烯及其衍生化反应,并展望了该领域今后的发展趋势.     

卤化富勒烯研究进展

自从C60被发现并能被大量制备以来,富勒烯化学已成为有机化学学科发展最快的领域之一.富勒烯通过多加成反应形成具有独特结构和性能的富勒烯卤化物和全氟烷基化物,为设计合成新型富勒烯基功能材料开辟了新方向.本文综述了近几年来在卤化富勒烯和全氟烷基化富勒烯的合成方法、结构及性能方面取得的最新进展,重点介绍了氟化富勒烯及其衍生化反应,并展望了该领域今后的发展趋势.     

[60]富勒烯衍生物的对称性、碳笼结构与C NMR谱

本文全面综述了多种[60]富勒烯衍生物的结构,阐述了(13)~C NMR谱在[60]富勒烯衍生物结构表征中的应用,重点讨论了不同对称性[60]富勒烯衍生物的(13)~C NMR谱图特征.通过[60]富勒烯部分(13)~C共振线的化学位移、数目和相对强度,可以确定[60]富勒烯衍生物的对称结构和加成方式.对于C_s、C_(2v)和C_(3v)对称性的[60]富勒烯衍生物,镜面上的碳原子的相对化学位移很大程度上取决于他们距加成位置的距离.因此,(13)~C NMR谱在碳笼具体结构的确定中具有不可替代的作用.     

[60]富勒烯衍生物的对称性、碳笼结构与13C NMR谱*

本文全面综述了多种[60]富勒烯衍生物的结构,阐述了(13)~C NMR谱在[60]富勒烯衍生物结构表征中的应用,重点讨论了不同对称性[60]富勒烯衍生物的(13)~C NMR谱图特征.通过[60]富勒烯部分(13)~C共振线的化学位移、数目和相对强度,可以确定[60]富勒烯衍生物的对称结构和加成方式.对于C_s、C_(2v)和C_(3v)对称性的[60]富勒烯衍生物,镜面上的碳原子的相对化学位移很大程度上取决于他们距加成位置的距离.因此,(13)~C NMR谱在碳笼具体结构的确定中具有不可替代的作用.     

C60RuH2(CO)(PPh3)配合物的合成和氧化还原性能研究

自从1985年Kroto等人发现C60等碳原子簇以来,在化学、物理以及材料科学掀起了富勒烯的研究热潮。目前富勒烯配合物的制备及其性质的研究是富勒烯化学最为活跃的研究领域之一,人们正致力于探索富勒烯各类衍生物的结构与性质之间的依赖关系,以期合成出具有特殊性能的富勒烯配合物,为富勒烯的实际开发应用奠定基础。本文合成表征了C60RuH2(OH)(PPh3)配合物,研究了其氧化还原特性。     

富勒烯/环糊精复合物及其在生物医药领域的应用

富勒烯有着独特的球形结构,这一结构赋予了其优异的光电及生物性能,在生物医药领域备受关注。环糊精具有良好的水溶性和生物相容性,锥筒状结构赋予了其特异性包合作用,在主客体化学中有着非常重要的地位。富勒烯/环糊精的复合物,结合了富勒烯和环糊精的优势,在DNA切割,光动力学疗法,药物载体等领域发挥了重要作用。本文从富勒烯与环糊精体系的构筑出发,综述了富勒烯/环糊精非共价包合物及共价偶联物在生物医药领域应用的研究进展,且对富勒烯/环糊精复合物的应用进行了展望,为构建新型富勒烯/环糊精复合物提供参考。     

η2-C60[RhCl(CO)(PPh3)2]配合物的合成与表征

从1985年Smalley等[1]发现C60等富勒烯至1996年富勒烯的发现者获诺贝尔化学奖期间, 在化学、 材料、 物理等领域形成了富勒烯的研究热潮[2～5]. 现在科学工作者正以较大的注意力投向富勒烯的化学修饰, 研究富勒烯各类衍生物的结构与性能之间内在联系规律, 以期望在开发应用方面取得突破性进展, 为此也十分重视对具有特殊组成与结构的富勒烯衍生物的研究. 本文首次合成出η2-C60[RhCl(CO)(PPh3)2]配合物, 并对其结构进行了表征.     

Generation of basis sets with high degree of fulfillment of the Hellmann-Feynman theorem

A direct relationship is established between the degree of fulfillment of the Hellman-Feynman (electrostatic) theorem, measured as the difference between energy derivatives and electrostatic forces, and the stability of the basis set, measured from the indices that characterize the distance of the space generated by the basis functions to the space of their derivatives with respect to the nuclear coordinates. On the basis of this relationship, a criterion for obtaining basis sets of moderate size with a high degree of fulfillment of the theorem is proposed. As an illustrative application, previously reported Slater basis sets are extended by using this criterion. The resulting augmented basis sets are tested on several molecules finding that the differences between energy gradient and electrostatic forces are reduced by at least one order of magnitude.     

The virial theorem as an entail for Koopmans' theorem in atomic calculations

The frozen approximation in the Koopmans' theorem suggests that the virial theorem is not obeyed. By imposing the virial theorem to Koopmans' theorem, we observe that the ionization potential of an atomic orbital is directly related to the respective kinetic energy and that the virial theorem introduces some reorganization effect on the electronic cloud. The quantity of reorganization introduced is not hazard, depending on the type of atom as well as the atomic orbital.     

Hypervirial theorems and symmetry

It is pointed out that to ensure that an optimal variational wave function having a certain symmetry satisfies the hypervirial theorem forW, it is sufficient thatiSW, whereS is the projector onto the symmetry type in question, be a possible variation of . Application is made to the tensor hypervirial theorem for atoms.     

Integral and regional virial theorems in density functional theory

Integral forms of the virial theorem in the density functional theory are derived. A relationship between the orbital energy sum and the integral of the pressure is studied. A new form of the regional virial theorem and the regional analogue of the Levy-Perdew relation are obtained. Local density approximation to the regional virial theorem is presented.     

A modification of Koopmans' theorem by imposition of the virial theorem in molecules

Imposition of the virial theorem on Koopmans' theorem permits the introduction of some relaxation effect in the electronic cloud of atomic (less than 5%) or molecular (less than 1.3% for the systems studied) systems and a partitioning of the ionization energy. The method is applied in some diatomic hydrides. It is observed that the imposition of the virial theorem improves the ionization of the innermost molecular orbitals significantly, while the improvement is negligible for the outermost orbitals. The ionization energy is divided among three different terms that elucidate some aspects of the nature of the ionization process.     

Particles and holes in the unitary group method

Based on the definition for complementary Gel'fand states, we proved the simple relationship between the matrix elements of particle states and those of hole states by unitary calculus.     

Hypervirial theorems and restrictions on wave functions

The conditions that ensure that an optimal variational wave function ø under general restricting requirements satisfies the hypervirial theorem are analysed. Application is made to a system where thez -component of angular momentum is a constant of motion and results are discussed in connection with those obtained via symmetry considerations.     

Energy-density relations in momentum space

The integrated Hellmann-Feynman theorem is used to derive a rigorous relation between the energy and the electron density in momentum space. Choosing the electron mass as a differential parameter, we obtain a formula corresponding to the Wilson-Frost formula in coordinate space. Analysing the mass-dependence of momentum density, we then show that the present formula is equivalent to one of the previous results deduced from the virial theorem. Use of the integral Hellmann-Feynman theorem is also discussed. Several illustrative examples are given for the calculation of energy from momentum density.     

Energy-density relations in momentum space. III. Variational aspect

A variational formula for the momentum density is derived by using the Hellmann-Feynman theorem and by introducing a reference system whose Hamiltonian differs only in the kinetic energy part from that of the original system. As simple applications of the present results, the reduced mass correction and the relativistic correction for the hydrogen-like atom are discussed.