Rate constants and isotope effects for the CH3+H2 → CH4+H reaction by an approximate semiclassical initial-value representation method

Rate constants and kinetic isotope effects are calculated for the CH3+H2 → CH4+H reaction by two theoretical methods: variational transition state theory with semiclassical corrections for tunneling and an approximate (linearized) semiclassical initial-value representation method, recently proposed by H. Wang, X. Sun, W.H. Miller [J. Chem. Phys. 108 (1998) 9726]. The theoretical results agree well with each other and with the experimental data in the temperature range 500–1500 K. For high temperatures, the differences between the two theoretical rate constants arise from the more accurate treatment of dividing surface recrossings by Millerʹs method.