氮笼N_(12)的量子化学研究

Quantum Chemistry Study of Nitrogen Cages N_(12)

采用量子化学从头算方法研究了 7个氮笼 N1 2 ,其中包括以前文献中研究过的两个氮笼 N1 2 .在 RHF/6-3 1 G*理论水平下进行全构型优化、振动频率分析和热化学计算 .计算结果表明 ,7个结构均是势能面上的局域极小点 .N1 2 (D3d)是所有 7个笼状异构体中最稳定的 .能量分析表明 ,如果这些分子能够被合成 。

Nitrogen clusters have drawn considerable attention in recent years, because of not only their theoretical interest, but also their possible use as environmentally friendly high-energy-density materials(HEDMs). In this work, quantum chemical ab initio method has been applied to the study of seven cage-like N 12 isomers , including two previously studied nitrogen cages N 12 . Full geometry optimization, harmonic vibrational frequency, and thermodynamics calculations for seven different N 12 molecules have been performed at the RHF/6-31G * level of theory. The calculation results show that all of the seven structures were found to be local minima on the potential energy hypersurface at the RHF/6-31G *, and the cage-like N 12 with D 3d symmetry is the most stable in seven N 12 isomers. From the results presented here, it seems that there is not a direct relationship between the stability of the isomers and their symmetry. We also found that the five-membered ring is a fundamental stable structural unit for large even number nitrogen clusters. The more the five-membered rings, the more stable the isomer would be. In addition, the energy differences relative to six N 2 molecules are also calculated and it appears that these seven cage-like N 12 isomers would be very energetic materials. The present study would provide some theoretical data for synthesizing more stable nitrogen clusters in the future.