Pu-N与Pu-O-H体系的分子结构和势能函数

【作者】 李跃勋；

【导师】 高涛；

【作者基本信息】 四川大学 ， 原子与分子物理， 2005， 硕士

【摘要】 本文采用量子力学中密度泛函（DFT）B3LYP方法和Pu的相对论有效原子实势模型（RECP）,应用Gaussian98和Gaussian03程序,对钚化合物（PuN,PuO,PuH,PuN₂和PuOH）的分子结构和分析势能函数进行了计算和研究,同时,还用量子力学从头计算的方法计算了PuOH体系的热力学函数,并在此基础上分析了PuOH体系的热力学稳定性。 在原子分子反应静力学基础上,根据分子电子状态构造的群论原理,推导得到了PuN,PuO,PuH,PuN₂和PuOH的可能的电子状态及合理的离解极限,并通过量子力学从头计算的方法确定了它们的基电子态分别为PuN（X⁶∑⁺）,PuO（X⁵∑-）,PuH（X⁸∑⁺）,PuN₂（X³∑_g^-）和PuOH（X⁶∑⁺）。且结构优化的结果得出其分子的最稳态构型分别为C_∞Ⅴ,C_∞Ⅴ,C_∞Ⅴ,D_∞h和C_∞Ⅴ, 导出了PuN,PuO和PuH双原子分子的Murrell-Sorbie势能函数曲线,在此基础上推导出光谱数据和力常数。并使用多体展式理论方法,首次导出了三原子分子（PuN₂和PuOH）两个构型的分析势能函数,它们的势能面准确地再现了稳态平衡结构构型及能量关系,除此之外,还复现了亚稳态结构构型和能量关系。本文还利用势能函数等值图讨论了两个三原子分子一些反应通道的静态特征。 论文的最后一章,用量子力学方法计算了PuOH体系的热力学数据,并对PuOH体系的热力学稳定进行了计算分析。从而探讨了钚、氧、氢体系中钚的腐蚀情况:H（g）+O（g）+Pu（S）→PuOH（g）,Pu（S）+OH（g）→PuOH（g）,PuH（g）+O（g）→PuOH（g）三个反应通道均能自发反应,而PuO（g）+H（g）→PuOH（g）在整个温度范围内都不能自发反应,这说明由气态H原子与PuO分子能很难反应生成PuOH气体。更多还原

【Abstract】 By using Density functional method B3LYP with SDDRECP constructured for Pu and Gaussian 98 and Gaussian 03, the equilibrium geometric structures and analytical potential energy functions for the plutonium compounds (PuN, PuO, PuH, PuN2 and PuOH) have been computed and studied in this paper. Besides, the thermodynamic functions (between 298.15K and 998.15) for PuOH system have been calculated out by using ab initio method. Moreover, thermodynamic stability of this system has also been analyzed.Firstly, the possible electronic states and the reasonable dissociation limits for plutonium compounds have been derived based on the atomic and molecular reaction statics and the group theoretical derivation of molecular electronic states. Then, the molecular structures for PuN, PuO, PuH, PuN, and PuOH have been optimized by using ab initio method, and the corresponding ground states and geometric structures are PuN(X6∑+, C∞v), PuO(X5∑-, C∞v), PuH(X8 ∑+, C∞v), PuN2 ( X3∑g-, D∞h) and PuOH (X6∑+, C∞v), respectively.The Murrell-Sorbie potential energy functions for the diatomic molecules PuN, PuO and PuH have been obtained according to the ab initio data through the last-square-fitting. The spectroscopic data and force constants for PuN, PuO and PuH have been derived from the potential energy functions. The analytical potential energy function for two structures of 3-atomic molecules (PuN2, PuOH) have also been derived by using many-body expansion method and they all successfully represent the equilibrium structures of ground states for 3-atomic molecules (PuN2, PuOH). Besides, they also describe the geometric structures and energy for the metastable structures of 3-atomic molecules. Moreover, molecular reaction kinetics of two 3-atomic molecules (PuN2, PuOH) based on these potential energy functions has been discussed in this paper.In the last section of this work, based on the RECP for Pu atom and the basis sets 6-311+G* and 6-311++G** for O and H atoms, respectively, the thermodynamic functions (between 298.15 and 998.15) for PuOH(g) molecule have been calculated by using density functional mouthed (B3LYP), and the formed thermodynamic function for PuOH(g) have also been worked out by thermodynamic method. Moreover, we have discussed the thermodynamic stability of PuOH(g) based on these data. Finally, we discussed the corrosion of plutonium in the Pu, O and H system. The results show that the reactions (H(g)+O(g)+Pu(s) → PuOH(g), Pu(s)+OH(g) → PuOH(g), PuH(g)+O(g)→PuOH(g) ) can react spontaneously between the temperature range (298.15 ~ 998.15). However, the reaction PuO(g)+H(g) → PuOH(g) can not react spontaneously between the same temperature range. This means that PuOH molecule cannot be formed through the reaction PuO(g)+H(g) →PuOH(g) or PuO molecule is so stable in chemical property that it is difficult for PuO molecule to react with H atom gas.更多还原