Physical Properties of Specially Designed Solid

在本项目中，我们获得了以下主要课题。(1)碳纳米管的拉曼光谱：我们研究了碳纳米管的拉曼光谱与直径和手性的关系。基于三维力常数张量，计算了单壁碳纳米管的声子色散关系。利用计算得到的声子色散关系，在键偏振理论的范围内，计算了入射光和散射光的某些偏振态下的拉曼强度。总结该项目，我们写了一本书“碳纳米管的物理性质”在Dresselhaus教授的合作。本书将于1998年7月由帝国理工出版社出版. (2)纳米石墨团簇中的过剩锂离子我们计算了锂离子掺杂在纳米石墨团簇中的电子结构，这些纳米石墨团簇的边缘具有悬挂键或氢终止。计算结果表明，锂离子与碳原子之间既有共价键，也有离子键，这可能有助于解释^7Li NMR奈特位移谱的宽信号。特别地，即使在氢终止的边缘处也可以进行Li嵌入。我们认为团簇边缘表面在无序石墨系统中容纳过量Li离子方面起着特殊的作用。我们现在将这个故事扩展到纳米石墨簇的F嵌入。

In the current project we have obtained the following main subjects.(1) Raman Intensity of Carbon Nanotube.We have invesitigated the Raman spectra of the carbon nanotubes as a function of diameter and chirality. We have calculated teh phonon dispersion relation of single wall carbon nanotubes based on the three dimensional force constant tensor. Using the phonon dispersion relation calculated, Raman intensity is calclated within the bond-polarization theory on some polarization configurations of the incident and scattered lights. Summarizing the project we have written the book "Physical Properties of Carbon Nanotubes" in the collaboration of Professor Dresselhaus. This book will be publised from the Imperial College Press by the July 1998.(2) Excess Li Ions in Nano-Graphite clusterWe have calculated the electronic structure of Li ions doped in a nano-graphite cluster with dangling bonds or hydrogen terminations at the edge surrounding the cluster. The calculations imply both covalent and ionic bonds of Li ions to carbon atoms, which may be relevant to explaining the broad signal of the ^7Li NMR Knight shift spectra. Li intercalation, in particular, is possible even at the hydrogen-terminated edges. We propose that the cluster edge surface plays a special role in accommodating excess Li ions in the disordered graphitic system. We are now extending the story to F intercalation to nano-graphite clusters.