PdH2、YH2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PdH2和YH2体系的结构进行优化计算,得到PdH2分子最稳态为C2v构型,电子组态为1A1,平衡核间距RPdH=0.1692 nm,键角∠HPdH=29.4°,离解能De=5.5212 eV,基态简正振动频率:ν1(b2)=1470.1 cm－1、ν2(a1)=1007.9 cm－1、ν3(a1)=2907.0 cm－1.YH2分子最稳态也为C2v构型,电子组态2A1,RYH=0.1962 nm,∠HYH=114.3°,De=5.6691 eV,基态简正振动频率:ν1(b2)=1457.9 cm－1、ν2(a1)=476.0 cm－1、ν3(a1)=1506.3 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PdH2和YH2分子的势能函数,其等值势能面图准确地再现了PdH2和YH2分子的结构特征和离解能,由此讨论了Pd ＋ H2和Y ＋ H2分子反应的势能面静态特征.

Structures and Potential Energy Functions of PdH2 and YH2 Molecules

Density functional(B3LYP) method has been used to optimize the possible structures of PdH2 and YH2 molecules by contracted valence basis set(SDD) for Pd and Y atoms, the 6-311＋＋G** basis set for H atom. The results show that the ground state of PdH2 molecule is C2v symmetry and X 1A1 state. The parameters of structure and the harmonic frequencies are RPdH=0.1692 nm, ∠HPdH=29.4°, De=5.5212 eV and ν1=1470.1 cm－1,ν2=1007.9 cm－1,ν3=2907.0 cm－1 respectively. The results also show that the ground state of YH2 molecule is C2v symmetry and X 2A1 state. The parameters of structure and the harmonic frequencies are RYH=0.1962 nm,∠HYH=114.3°, De=5.6691 eV and ν1=1457.9 cm－1,ν2=475.9 cm－1,ν3=1506.3 cm－1 respectively. The potential energy functions of PdH2 and YH2 have been derived from the normal equation fitting and the many-body expansion theory which is successfully used for describing the equilibrium geometry of PdH2 and YH2.Molecular reaction kinetics of Pd ＋ H2 and Y ＋ H2 based on this potential energy function is discussed briefly.