N5H5异构体的结构与稳定性的理论研究

采用密度泛函理论的B3LYP方法在6-311++G**基组水平上对N5H5氮氢化合物异构体可能存在的构型进行了几何优化, 得到23种稳定异构体, 并研究了这些异构体间可能的互变异构情况. 为了讨论N5H5异构体作为含能材料候选物质的可能性, 还采用了G3B3方法计算了能量, 并且计算了异构体的生成热(⊿Hf,298).结果表明, 在23种异构体中链状异构体最稳定, 四元环四氮烷异构体最不稳定, 存在一个N=N双键的异构体较同类异构体能量低, 较为稳定; N5H5氮氢化合物的生成热均为正, 其中异构体E1生成热最高. 估算了N5H5的摩尔体积, 由密度公式ρ=MT/Vmol,得到E1 的密度最大.

Theoretical Study on the Structures and Stabilities of the N5H5 Isomers

Twenty-three possible steady isomers of N5H5 were optimized at 6-311++G** level using the density functional B3LYP method, and tautomerisms between them were discussed. To discuss the possibility of N5H5 isomers as candiate of energetic materials, energies and heats of formation were calculated by the G3B3 method. The results indicated that chain isomers were the most stable isomers and the isomer containing a tetrazetinyl group was the most unstable isomer. The existence of N=N double bonds were beneficial to their stabilities. The formation heats of all conformers were positive, and isomer E1 had the highest formation heat. In addition, at 6-311++G** level by the B3LYP method the molar volume of N5H5 was estimated, and from the density formula: ρ=MT/Vmol, we could know that the density of E1 was the largest.