PdH、PdH2分子的结构与势能函数

用相对论有效原子实势(SDD)和密度泛函(B3LYP)方法对PdH和PdH2体系的结构进行了优化,计算表明:PdH分子的几何构型为C∞v,其基态为X2∑+态,键长R=0.154 11 nm,离解能为De=2.511 0eV,谐振频率ωe=2 156.226 9 cm-1,并拟合得到Murrell-Sorbie势能函数;PdH2分子稳态为C2y构型,电子组态为1A1,平衡核间距RPdH=0.151 73 nm,键角∠HPdH=72.373 3°,基态简正振动频率:对称伸缩振动频率v1(b2)=2 104.369 6 cm-1、弯曲振动频率v2(a1)=528.742 6 cm-1、反对称伸缩振动频率v3(a1)=2 208.649 0 cm-1,离解能De=5.318 56 eV.在此基础上,用Murrell-Sorbie函数和多体展式理论导出PdH(C∞v,X2∑+)、PdH2(C2v,1A1)分子的解析势能函数.其等值势能面图准确地再现了PdH2分子的结构特征和离解能,由此讨论了Pd+H2分子反应的势能面静态特征.

Structures and potential energy functions of PdH and PdH2 molecule

Density functional (B3L YP) method with relativistic effective core potential (RECP) has been used to optimize the structures of PdH and PdH2mmolecules. The results show that the ground states of PdH and PdH2 molecules are of Coou and C2u symmetry and of 2∑+ and 1 A1 respectively. The spectral constants of PdH, we=2019.4589cm-1, weXe=41.4035cm-1 and the harmonic frequencies of PdH2u1(b2)=2104.3696cm-1,u2(a1)=528.7426cm-1,u3(a1)=2208.6490cm-1 have also been obtained on the B3L YP/SDD level. The potential energy functions of PdH(Coou,X2∑+ and PdH2v,1A1) have been derived for the first time from normal equation fitting and the many-body expansion theory. Molecular reaction kinetics of Pd+H2 based on this potential energy function is discussed.