接枝羧基对单壁碳纳米管弹性性质的影响

Effects of the Grafted Carboxyl on the Elastic Properties of Single-walled Carbon Nanotubes

采用分子动力学方法对端口接枝不同数量羧基的扶手椅型和锯齿型单壁碳纳米管弹性模量进行了模拟研究.结果表明,扶手椅型(5,5)、(10,10)管和锯齿型(9,0)、(18,0)管在未接枝状态下杨氏模量分别为948、901GPa和804、860GPa.在接枝2-8个羧基情况下,扶手椅型单壁碳纳米管拉伸杨氏模量基本不随接枝数量的增加而发生变化,而锯齿型单壁碳纳米管则不同,接枝状态下的弹性模量比未接枝状态小很多,但随接枝数量的增加又呈略增趋势.分别从接枝后碳纳米管变形电子密度等值线结构变化、键长变化和系统势能变化规律等方面,对单壁碳纳米管弹性模量的接枝效应进行了分析.

The molecular dynamics method was used to investigate the elastic properties of armchair and zigzag single-walled carbon nanotubes grafted by carboxyls on their ports. The results showed that the Young＇ s moduli of ungrafted armchair （5, 5）, （10, 10） and zigzag （9, 0）, （18, 0） single-walled carbon nanotubes were 948, 901 GPa and 804, 860 GPa, respectively. When the single-walled carbon nanotubes were grafted by 2 to 8 carboxylic functional groups, the Young＇s modulus of the armchair single-walled carbon nanotubes had few varieties, while the zigzag single-walled carbon nanotubes were different, namely, the Young＇s modulus of the nanotubes decreased significantly due to the grafting and the Young＇ s modulus increased appreciably with increasing of the grafts. The reasons were analyzed in terms of the isoline structure of deformation electron density, the bond-length and the system potential energy varieties of the carbon nanotubes with different graft numbers.