扶手椅型单壁碳纳米管生长机理的研究

Theoretical Study on the Growth Mechanism of Armchair Single-walled Carbon Nanotube

用Gaussian03程序中的AMI方法对扶手椅型单壁碳纳米管的生长机理进行了研究．结果表明,若碳纳米管生长的碳源是C2自由基,则有一条反应途径可能是:C2自由基首先与碳纳米管的开口端形成一个中间体,然后该中间体经过一个过渡状态,形成产物;从(3,3),(4,4),(5,5)到(6,6),其生长反应的活化能逐渐降低．同时研究发现,活化能的高低与碳纳米管共轭程度的大小有关,碳纳米管的共轭程度越大,活化能越低;在靠近新形成的六元环的两侧,碳纳米管可能优先继续生长．

The growth mechanism of armchair single-walled carbon nanotube has been studied theoretically by AM1 method as implemented in Gaassian03 program. The following results were obtained. （l） Let C2 radicals be the carbon source for the growth of the carbon nanotube, then the most likely growth mechanism would be as follows. An intermediate is formed firstly by the direct addition of C2 radical to the open end of the carbon nanotube without an energy barrier, then via a transition state the reaction produces the product, i.e., C2 becomes the component of the hexagon of the nanotube. （2） From （3,3） to （6,6）, the activation energy decreases （from 66.8 to 46.1 kJ·mol ^-1）, whereas the conjugation of the nanotube increases. （3） The distribution of the frontier molecular orbitals indicates that the two edges of the newly formed hexagon maybe grow easily.