中文摘要：

首先建立有限长两端开口、一端封闭、两端封闭的（5，5）型单壁碳纳米管的分子模型，采用原子替代方法得到氟掺杂结构．在此基础上，利用基于局域密度泛函理论的第一原理方法对其进行几何结构优化，再计算其结合能、费米能级和电子态密度等，从而讨论氟掺杂对三种碳纳米管场发射特性的影响．计算结果表明，掺氟后三种碳纳米管的费米能级明显升高，其中一端封闭的单壁碳纳米管的费米能级成线性增大，两端封闭的单壁碳纳米管的费米能级升幅最大，且费米能级处的电子态密度较高，说明两端封闭和一端封闭的单壁碳纳米管经氟掺杂后比两端开口的单壁碳纳米管将在场发射上有着更好的应用前景．

英文摘要：

Based on the density-functional theory and the first-principle method, the field-emission properties of the opened, half-closed and closed armchair （5,5） single-walled carbon nanotubes （SCNTs） doped by fluorin element were calculated. A geometry optimization of SCNTs is performed first, then the variations of binding energy, Fermi level and the density of states（DOS） are calculated. It has been found that the binding energy of all SCNTs due to the doping increase significantly, thus the SCNTs doped by fluorin element has beautiful future in field-emission application. We also found out that the Fermi level of half-closed SCNTs doped by fluorin element increased linearly, the Fermi level of closed SCNTs doped by fluorin element increased mostly, and DOS near Fermi level was rather high, so that the closed and half-closed SCNTs doped by fluorin has more benefit than the opened SCNTs in field-emission properties.