CH2(X^3B1)和C2H(X^2∑g^＋)分子的结构与解析势能函数

Structure and analytic potential energy functions of the molecules CH_2 and C_2H

运用密度泛函理论(DFT)的B3LYP方法在6-311++G**水平上,对基态CH2、C2H分子的结构进行了优化计算,得到CH2分子的稳定结构为C2v构型,电子态为X3B1,平衡核间距RCH=0.1079 nm、离解能De=8.037 eV;C2H分子的稳定结构为C∞v构型,电子态为X2∑g+,平衡核间距RCH=0.1059 nm、RCC=0.1211 nm、离解能De=12.05 eV,用多体项展式理论推导了基态CH2和C2H分子的解析势能函数,其等值势能图准确再现了基态CH2和C2H分子的结构特征及其势阱深度与位置.

The density function （B3LYP） method has been used to optimize the possible ground-state structures of CH2and C2H molecules. The results show that the ground state of CH2 molecule has C2v symmetry and is in the X^3B1 state. The parameters of structure are RCH = 0. 1079 nm, De = 8. 037 eV, respectively. The results also show that the ground state of C2H molecule has C∞v symmetry and is in the X^2∑g^＋ state. The parameters of structure are RCH = 0. 1059 nm, RCC = 0. 1211 nm, De = 12.05 eV, respectively. The potential energy functions of CH2 and C2H have been derived from the many-body expansion theory. The potential energy functions describe correctly the configurations and the dissociation energies of the two ground-state molecules.