化学学报 ›› 2003, Vol. 61 ›› Issue (11): 1720-1723. 上一篇    下一篇

研究论文

α-Pb(N_3)_2晶体的周期性从头计算

居学海;肖鹤鸣;姬广富   

  1. 南京理工大学化学系
  • 发布日期:2003-11-15

Periodic ab initio Calculations of Crystalline α-Lead Azide

Ju Xuehai;Xiao Heming;Ji Guangfu   

  1. Department of Chemistry, Nanjing University of Science & Technology
  • Published:2003-11-15

叠氮化铅是最常用的起爆剂。对α-Pb(N_3)_2晶体首次进行ab initio周期性 计算,求得其能带和电子结构,探讨了结构、性能关系。原子间重叠布居和电荷密 度分析表明,铅离子与叠氮根离子末端氮原子(N_T)间的轨道重叠作用较强,部分 电子已从叠氮根转移到铅离子。经基组叠加误差(BSSE)较正求得α-Pb(N_3)_2的晶 格能为-2187.35 kJ/mol,与源自实验的文献值吻合。晶体前沿占有轨道主要由叠 氮根端位氮(N_T)的原子轨道(AO)组成,而前沿空轨道则主要由Pb~(2+)的AO组成, 这有助于N_T上电子直接向金属离子跃迁;根据“(电子)最易跃迁原理(PET)” 可预测α-Pb(N_3)_2的感度较大,适合于作起爆药使用。

关键词: 叠氮化铅, 晶体, 从头计算法, 能带结构, 电子结构

The energy bands, electronic stmctures and relationship between structures and properties of the ciystalline a-lead azide were investigated with periodic ab initio method. The atomic overlaps and electron densities show that there exists some covalency between the metal and the azide group. The ciystal lattice energy, corrected for the basis set supeiposition errors, is -2187.35 kj'mol"1. This value is in good agreement with that estimated by Gray's approximate method. Atomic charge on Pb~(2+) is actually ca. 1.27 a. u. , indicating that some electrons have been transferred from azide anion to lead cation in the a-Pb(N_3)_2 crystal. The frontier bands are uneven and crossed. The frontier occupied ciystal orbitals mainly consist of the atomic orbitals of the terminal nitrogen atoms of azide, while the frontier virtual crystal orbitals consist of those of lead, which facilitates the electron leap from the terminal nitrogen to lead. Consequently, a- Pb(N_3)_2 is expected to be sensitive explosives, according to the "principle of the easiest transition". It is thus suitable to be used as an initiating high explosive.

Key words: Pb(N_3)2, CRYSTALS, AB INITIO CALCULATION, BAND STRUCTURES, ELECTRONIC STRUCTURE

中图分类号: