PdYH分子的结构与势能函数

用密度泛函理论的B3LYP方法, 对钯和钇原子采用SDD收缩价基函数, 氢原子采用6-311＋＋G**全电子基函数, 对PdY和PdYH体系的结构进行优化. 计算表明: PdY分子的几何构型为C_∞v, 其基态为X²Σ^＋态, 键长R＝0.24168 nm, 离解能为D_e＝2.8261 eV, 谐振频率ω_e＝254.0656 cm^－1, 并拟合得到Murrell-Sorbie势能函数; PdYH分子最稳态为C_s构型, 电子组态为¹A', 平衡核间距R_PdY＝0.24281 nm, R_YH＝0.19824 nm, 键角∠PdYH＝116.7157°, 离解能D_e＝5.6146 eV, 基态简正振动频率: 对称伸缩振动频率ν₁ (a')＝348.2909 cm^－1, 弯曲振动频率ν₂ (a')＝243.3382 cm^－1, 反对称伸缩振动频率ν₃ (a')＝1442.2695 cm^－1. 由微观过程的可逆性原理分析了分子的可能离解极限. 并用多体项展式理论方法分别导出基态PdY和PdYH分子的势能函数, 其等值势能面图准确地再现了PdY和PdYH分子的结构特征和离解能, 由此讨论了Pd＋Y＋H分子反应的势能面静态特征.

Structures and Potential Energy Functions of PdYH Molecule

Density functional method (B3LYP) has been used to optimize the possible structures of PdY and PdYH molecules by contracted valence basis set (SDD) for Pd and Y atoms and the 6-311＋＋G** basis set for H atom. The results show that the ground states of PdY and PdYH molecules are X²Σ^＋ and X¹A' states, respectively. The equilibrium geometry R＝0.24168 nm, dissociation energy D_e＝2.8261 eV, and spectral constants ω_e＝254.0656 and ω_ex_e＝0.60391 cm^－1 of PdY (C_∞v) molecule have been obtained, respectively. For PdYH (C_s) molecule, the equilibrium geometry, dissociation energy and harmonic frequency were calculated, and the results show that R_PdY＝0.24281 nm, R_YH＝0.19824 nm, ∠PdYH＝116.7157° and D_e＝5.6146 eV, and ν₁ (a')＝348.2909 cm^－1, ν₂ (a')＝243.3382 cm^－1, ν₃ (a') ＝1442.2695 cm^－1, respectively. Analytical potential energy function for the PdYH has been derived for the first time using many-body expansion method, which was successfully used for describing the equilibrium geometry of PdYH. Molecular reaction kinetics of Pd(¹S_g)＋Y(²D_g)＋H(²S_g) based on this potential energy function is being studied under way.