PdPbH分子的结构与势能函数

Structure and potential energy function of PdPbH ground state molecule

在相对论有效原子实势近似下,用密度泛函理论的B3LYP方法,对钯和铅采用LANL2DZ基函数,氢原子采用6-311++G**全电子基函数,对PdPb、PdPbH分子的结构进行优化.计算表明:PdPb分子的基态为X1∑+,键长RPdPb=0.24536 nm,离解后Pd原子处于基态(单重态)而Pb原子处于激发态(单重态),离解能为3.107686 eV,引入开关函数拟合得到Murrell-Sorbie势能函数;PdPbH分子最稳态为Cs构型,电子组态为X2A′,键长RPdPb=0.2547 nm,RPdh=0.15919 nm,键角∠PbPdH=64.7856°,离解能De=4.79 eV.由微观过程的可逆性原理分析了分子的可能离解极限,并用多体项展开式理论方法分别导出基态PdPb和PdPbH分子的势能函数,其等值势能面图准确的再现了PdPb和PdPbH分子的结构特征和离解能,由此讨论了Pd+Pb+H分子反应的势能面静态特征.

Density function method（B3LYP） has been used to optimize the possible structures of PdPb and PdPbH molecules by basis set （LANL2DZ） for Pd and Pb atoms and the 6-311 ＋ ＋ G^＊＊ basis set for H atom. The results show that the ground states of PdPb and PdPbH molecules are X ^1 ∑^ ＋ and X ^2A′ states, respectively. The equilibrium geometry of PdPb molecule is Rpdpb = 0. 24536 nm, the Pd atoms is the ground states （singlet state） and the Pb atom is the excited states （singlet state） after the PdPb molecule is dissociated, the dissociation energy is 3.107686 eV. The switch function was introduced into the calculation, and then Murrell-Sorbie analytical potential energy function for the PdPb was derived by normal equations. For PdPbH（Cs） molecule, the equilibrium geometry and the dissociation energy were calculated, the results show that Rpdpb = 0. 2547 nm, Rpdh = 0. 15919 nm, LPbPdH = 64. 7856^＊, and D, = 4.79 eV, respectively. Analytical potential energy function for the PdPbH has been derived for the first time using many-body expansion method, which was sueeessfuUy used for describing the equilibrium geometry of PdPbH. Molecular reaction kinetics of Pd ＋ Pb ＋ H based on this potential energy function is being studied under way.