Structure and analytic potential energy function of the molecule CH2

The density function(B3LYP) method has been used to optimize the possible ground-state structures of CH2 molecule.The results show that the ground state of CH2 molecule has C2v symmetry and is in the X3B1 state.The parameters of structure are RCH=0.1072 nm,De=8.034 eV,respectively.The potential energy function of CH2 has been derived from the many-body expansion theory.The potential energy function describes correctly the configuration and the dissociation energy of the ground-state CH2 molecule.