Zakai Itai, Grinstein Dan, Welner Shmuel, Gerber R Benny
Institute of Chemistry and The Fritz Haber Research Center , The Hebrew University , Jerusalem 9190401 , Israel.
Department of Chemistry , University of California , Irvine , California 92697 , United States.
J Phys Chem A. 2019 Aug 29;123(34):7384-7393. doi: 10.1021/acs.jpca.9b03704. Epub 2019 Aug 20.
There is much current interest in materials that are made entirely or mostly of nitrogen atoms. Such materials, polynitrogens, may reveal new aspects of nitrogen chemistry, and are believed to provide a possible basis for novel energetic substances. An interesting family of such materials, in which the N group appears as a cation, was prepared by K. O. Christe and co-workers. Little is known as yet on the microscopic properties of these materials. In this paper, we report theoretical calculations to predict the structure, energetic stability and decomposition dynamics of the polynitrogen molecule NB(N), the building block of a solid prepared by Christe, and of the dimer of this molecule. The structures are computed at the B3LYP-D3 level of DFT. molecular dynamics simulations are used to explore the thermal stability of the species and the decomposition mechanism. It is found that the NB(N) ion-pair decomposes on a picosecond time scale at = 200 K, with an ultrafast release of four N molecules, which is very exothermic. The species B(N) is a product. The dimer is considerably more stable. Sensitivity of the process to temperature and to an applied force is reported. Possible applications of this material are briefly discussed.
目前人们对完全由氮原子构成或大部分由氮原子构成的材料有着浓厚的兴趣。这类材料，即多氮化合物，可能会揭示氮化学的新方面，并被认为为新型含能物质提供了可能的基础。K. O. 克里斯蒂及其同事制备了一类有趣的此类材料，其中N基团以阳离子形式出现。目前对这些材料的微观性质了解甚少。在本文中，我们报告了理论计算结果，以预测多氮分子NB(N)（克里斯蒂制备的一种固体的基本结构单元）及其二聚体的结构、能量稳定性和分解动力学。结构是在DFT的B3LYP-D3水平上计算的。分子动力学模拟用于探索这些物质的热稳定性和分解机制。结果发现，NB(N)离子对在200 K时在皮秒时间尺度上分解，超快释放出四个N分子，这是一个非常放热的过程。产物是物种B(N)。二聚体则稳定得多。报告了该过程对温度和外力的敏感性。还简要讨论了这种材料的可能应用。
