Test of variational transition state theory with multidimensional tunneling contributions against an accurate full-dimensional rate constant calculation for a six-atom system

We present calculations of the H+CH4 reaction rate on the Jordan–Gilbert surface using canonical variational transition state theory with microcanonical optimized multidimensional tunneling contributions (CVT/μOMT). The purpose of the calculation is to compare the results to the recent accurate dynamical calculations of Bowman, Wang, Huang, Huarte-Larrañaga, and Manthe for this potential energy surface. Over the full 200–500 K range for which accurate results are available we find a mean absolute deviation of only 17% and a maximum absolute deviation of 23%. This provides a rigorous validation of this popular method for a larger system than has previously been possible and indicates that previous validations for atom–diatom reactions were indeed indicative of the kind of accuracy one can obtain for larger systems.