PuNO分子结构与势能函数

本文运用密度泛函理论的B3LYP方法, 对钚原子应用LANL2DZ收缩价基函数, 氮、氧原子采用AUG-cc-pVTZ基函数, 分别对PuN, PuO, NO和PuNO体系进行了结构优化, 得到PuNO分子最稳构型为C_∞v (Pu-N-O), 电子态为⁶Σ^- (基态), 平衡核间距R_ON=0.12257 nm, R_NPu=0.22951 nm, 离解能D_e=8.10537 eV. 同时优化得到PuNO 分子存在两种亚稳态平衡构型分别为C_∞v (Pu-O-N), ⁶Σ^- (电子态)和C_s (O-Pu-N), A" (电子态), 以及分子体系相应的力学常数等. 拟合出PuN, PuO 和NO 分子的Murrell-Sorbie势能函数, 并使用多体项展式理论得到了PuNO分子的分析势能函数, 其等值势能图准确再现了PuNO分子最稳态构型及两个亚稳态构型的离解能和结构特性, 由此讨论了该分子体系的势能面静态特征.

Structure and potential energy function of PuNO molecules

Density functional (B3LPY) method has been utilized to optimize the possible structures of PuN, PuO, NO and PuNO molecules using the contracted valence basis set (LANL2 DZ) for Pu atom, and the AUG-cc-pVTZ basis set for N and O atoms. It is shown that the ground state of the PuNO molecules has C_∞v (Pu-N-O) symmetry and the ground electronic state is ⁶Σ^-. The equilibrium nuclear distances for Pu-N and N-O bonds in the PuNO molecules are R_PuN=0.22951 nm and R_NO=0.12257 nm, and the dissociation energy is D_e=8.10537 eV. Furthermore, the other two metastable states of the PuNO molecules are also obtained, and the electronic states of the two configurations are ⁶Σ^- and A" with C_∞v (Pu-O-N) and C_s (O-Pu-N) symmetry, respectively. Then the Murrell-Sorbie potential energy functions of the PuN, PuO and NO molecules have been simulated and the analytical potential energy function of the PuNO molecules has been derived using the many-body expansion theory. The contours of the potential energy functions reproduce exactly the most stable equilibrium structures, the two metastable state structures as well as the dissociation energy of the PuNO molecules. The molecular static reaction pathway, based on the potential energy function, is also discussed.