Ground state for CH2 and symmetry for methane decomposition

Abstract

Using the different level of methods B3P86, BLYP, B3PW91, HF, QCISD, CASSCF (4,4) and MP2 with the various basis functions 6-311G**, D95, cc-pVTZ and DGDZVP, the calculations of this paper confirm that the ground state is X̃3B1 with C2v group for CH2. Furthermore, the three kinds of theoretical methods, i.e. B3P86, CCSD(T, MP4) and G2 with the same basis set cc-pVTZ only are used to recalculate the zero-point energy revision which are modified by scaling factor 0.989 for the high level based on the virial theorem, and also with the correction for basis set superposition error. These results are also contrary to X̃3Σ−g for the ground state of CH2 in reference. Based on the atomic and molecular reaction statics, this paper proves that the decomposition type (1) i.e. CH4 → CH2+H2, is forbidden and the decomposition type (2) i.e. CH4 → CH3+H is allowed for CH4. This is similar to the decomposition of SiH4.