杂原子掺杂的含单空位缺陷BN纳米管的非线性光学性质

采用密度泛函理论(DFT)研究了杂原子M(M=Li, Na, K, Be, Mg, Ca, C和Si)在B/N单空位缺陷处的掺杂对(6,0)BN纳米管体系非线性光学性质的影响. 采用B3LYP方法共得到了14种几何构型, 并采用BHandHLYP方法计算了这些结构的第一超极化率β₀值. 研究结果表明, 单纯的B或N缺陷几乎不影响BN纳米管体系的非线性光学性质; 与B缺陷处掺杂的体系相比, 杂原子在N缺陷处的掺杂更有利于提高BN纳米管体系的第一超极化率β₀值; 对于同周期掺杂原子, 还原性越强的原子掺杂对BN纳米管体系的第一超极化率β₀值的改善越明显, 表现为β₀(Ⅰ族)>β₀(Ⅱ族)>β₀(Ⅳ族); 对比同主族掺杂原子, 第三周期元素Na和Mg的掺杂能更有效地提高体系的第一超极化率β₀值, 原因主要在于原子半径和还原性等因素共同决定其对BN纳米管体系第一超极化率β₀值的改善程度. 本文研究结果为有效提高BN纳米管体系的非线性光学性质提供了一种新思路, 为基于BN纳米管的非线性光学材料设计提供了有价值的理论信息.

Investigation on Nonlinear Optical Properties of Foreign-atom Doping Boron Nitride Nanotube with Vacancy Defects

The geometrical structures and nonlinear optical(NLO) properties of fourteen foreign-atom-doping (6,0) boron nitride nanotubes with B/N vacancy defect, M-Va-BNNT(a=B and N; M=Li, Na, K, Be, Mg, Ca, C and Si), were investigated with the density functional theory(DFT) method. The computational results reveal that the B/N vacancy defect almost has no effect on the NLO properties of pristine boron nitride nanotube(BNNT). Compared with the BNNT with B vacancy defect, the foreign-atom doped at the N vacancy can more effectively increase the β0 value of BNNT. The doping atom with the stronger reducing property in the same row can cause a larger improvement on the β0 value of BNNT with N vacancy, namely, β0(group Ⅰ)>β0(group Ⅱ)>β0(group Ⅳ). The reducing properties and atomic radius of the doping atoms in same family have a cooperation effect on the β0 value of the BNNT, and the resulted case is that the doping Na and Mg atoms in the third row at N-vacancy can cause a larger β0 value of the BNNT than the other atoms in the same family. These computational results will provide the new ideas and useful theoretical information for the designing of new type of high-performance NLO materials based on BNNTs.