A ten-dimensional quantum dynamics model for the X + YCAB₂ reaction: Application to H + CH₄ reaction

The exact description of the prototypical X + CH₄ reactions in the framework of quantum mechanics is a long-standing challenge in chemical reaction dynamics. A number of reduced-dimensional models have been developed and advanced our understanding of polyatomic chemical reactivity. Here, we propose a new ten-dimensional (10D) quantum dynamics model for the kind of X + YCAB₂ reaction. The new model is an extension of our previous eight-dimensional (8D) model for the X + YCZ₃ reaction. In this 10D model, AB₂ holds C_2v symmetry and the group CAB₂ is assumed to keep C_s symmetry, which gives a better description of the rocking mode of methane than the previous 8D model. The reaction dynamics of H + CH₄ → H₂ + CH₃ is first investigated using this model. The calculations showed that the rocking mode has a similar reaction efficiency to the umbrella mode. For the degenerate asymmetric stretching mode, the averaged efficiency is comparable to that of the symmetric stretching mode.