中文摘要：

采用密度泛函理论的GGA/PW91方法对有限长Y型碳纳米管的结构和性质进行了研究.研究结果表明,由于缺陷环的影响,Y型碳纳米管与直型管的性质明显不同,而且,Y型碳纳米管的结构和性质与分支管长度存在一定的关系.当分支管长度大于1nm时,Y型碳纳米管的结构、能隙和电学性质均出现周期性振荡变化的趋势.

英文摘要：

The geometry and electronic structure of finite-length（4,4）Y-shaped carbon nanotubes（CNTs）were investigated using density functional theory with GGA-PW91 method.The results indicate that the difference between the Y-shaped CNT and the pristine one is remarkable due to the influence of the defects in the junctions of the former.Furthermore,the structures and properties of Y-shaped CNTs are found to be rela-ted to the length of the CNT branch.By comparing the properties of the Y-shaped CNTs with different lengths,the length-dependent oscillation behavior including structure,energy gap and electronic property were observed when the length is longer than 1 nm.