Ground state for CH2 and symmetry for methane decomposition

Using the different level of methods B3P86, BLYP、B3PW91, HF,QCISD、CASSCF (4,4) and MP2 with the various basis functions6-311G**, D95, cc--pVTZ and DGDZVP, the calculations of this paperconfirm that the ground state is $tilde {X}{ }^3B_1 $ with $C_{2v} $group for CH$_{2}$. Furthermore, the three kinds of theoreticalmethods, i.e. B3P86、CCSD(T, MP4) and G2 with the same basis setcc-pVTZ only are used to recalculate the zero-point energy revisionwhich are modified by scaling factor 0.989 for the high level basedon the virial theorem, and also with the correction for basis setsuperposition error. These results are also contrary to $tilde {X}{}^3Si _{rm g} ^ - $ for the ground state of CH$_{2}$ in reference.Based on the atomic and molecular reaction statics, this paper provesthat the decomposition type (1) i.e. CH$_{4}to $CH$_{2}$+H$_{2}$, isforbidden and the decomposition type (2) i.e. CH$_{4} to $CH$_{3}$+His allowed for CH$_{4}$. This is similar to the decomposition ofSiH$_{4}$.