Zhao Zhao-Yang, Wang Guo-Liang, Chen Xu-Dan, Qi Chun-Bao, Sun Xin-Li
Graduate School, Rocket Force University of Engineering, Xian, Shanxi, 710025, People's Republic of China.
Nuclear Science and Technology Laboratory, Rocket Force University of Engineering, Xian, Shanxi, 710025, People's Republic of China.
J Mol Model. 2021 Nov 26;27(12):363. doi: 10.1007/s00894-021-04983-y.
The study of the reaction between plutonium and nitrogen is helpful in further understanding the interaction between plutonium and air molecules. Currently, there is no research on the microscopic reaction mechanism of plutonium nitridation reactions. Therefore, the microscopic mechanism of the Pu with N gas phase reaction is explored in this study, based on density functional theory (DFT) using different basis functions. In this paper, the geometry of stationary points on the potential energy surface is optimized. In addition, the transition states are verified by frequency analysis and intrinsic reaction coordination (IRC). Finally, we obtained the reaction potential energy curve and micro reaction pathways. Analysis of the reaction mechanism shows that the reaction of Pu with N has two pathways. Pathway 1 (Pu + N → R1 → TS1 → PuN) has a T-shaped transition state and pathway 2 (Pu + N → R2 → TS2 → PuN + N) has an L-shaped transition state. Both transition states have only one imaginary frequency. According to the comparison of the energy at each stagnation point along the two pathways, and the heat energy emitted by the two reaction paths, we found that pathway 1 is the main reaction pathway. The nature of Pu-N bonding evolution along the pathways was studied by atoms in molecules (AIM) and electron localization function (ELF) topological approaches. In order to analyze the role of the plutonium atom 5f orbital in the reaction, the variation in density state along the pathways was measured. Results show that the 5f orbital mainly contributes to the formation of Pu-N bonds, and the influence of temperature on the reaction rate is revealed by calculating the rate constants of the two reaction pathways.
钚与氮反应的研究有助于进一步理解钚与空气分子之间的相互作用。目前，关于钚氮化反应的微观反应机理尚无研究。因此，本研究基于密度泛函理论（DFT），使用不同的基函数，探索了Pu与N气相反应的微观机理。本文优化了势能面上驻点的几何结构。此外，通过频率分析和内禀反应坐标（IRC）对过渡态进行了验证。最后，我们得到了反应势能曲线和微观反应路径。反应机理分析表明，Pu与N的反应有两条路径。路径1（Pu + N → R1 → TS1 → PuN）具有T形过渡态，路径2（Pu + N → R2 → TS2 → PuN + N）具有L形过渡态。两个过渡态都只有一个虚频。通过比较两条路径上各驻点的能量以及两条反应路径放出的热能，我们发现路径1是主要反应路径。利用分子中的原子（AIM）和电子定域函数（ELF）拓扑方法研究了沿路径的Pu-N键演化性质。为了分析钚原子5f轨道在反应中的作用，测量了沿路径的态密度变化。结果表明，5f轨道主要有助于Pu-N键的形成，并且通过计算两条反应路径的速率常数揭示了温度对反应速率的影响。
