第一性原理研究电场对BN纳米管电子结构的影响

采用基于密度泛函理论的第一性原理计算研究了电场对BN纳米管的电子结构的影响.首先对在不同电场强度下的纳米管几何结构进行了优化,可以看出纳米管沿轴方向层间距出现了不规则的变化.电子能带结构显示,在电场作用下,zigzag型和armchair型两种结构纳米管的能带向低能方向移动,并且导致纳米管的带隙有显著的减小.电场使得armchair型纳米管的带隙发生了从间接带隙向直接带隙的转变.在电场作用下,纳米管的两端态密度呈现出明显的差异,正负电荷沿轴向出现了沿轴向的空间分离,Mulliken电荷分布图揭示出最高占据轨道和最低未占据轨道分居在纳米管的两端.

Electric field effect on electronic structure of BN nanotubes: a first principles study

The electronic structure of BN nanotube under electric field was studied using first principles calculations based on density functional theory (DFT). The relaxed structures in the presence of an electric field show that the interlayer distance along tube axis varies irregularly. The energy band structure is shifted towards the lower energy level, and the band gap is decreased significantly for both armchair and zigzag nanotubes by applied electric field. Furthermore, for armchair nanotube, the band gap transition from indirect-to-direct is observed. It can be found that there is obvious difference in partial density of states (PDOS) between half left and half right sides of nanotube. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicate that the positive and negative charges are spatial separated along the nanotube axis with the effect of electric field, and thus this can be considered as a pure material PN junction without doping.