Surface for methane combustion: O(³P) +CH₄ OH+CH₃*

Kinetic investigations including quasi-classical trajectory and canonical unified statistical theory method calculations are carried out on a potential energy surface for the hydrogen-abstraction reaction from methane by atom O(P-3). The surface is constructed using a modified Shepard interpolation method. Theab initiocalculations are performed at the CCSD(T) level. Taking account of the contribution of inner core electrons to electronic correlation interaction inab initioelectronic structure calculations, modified optimized aug-cc-pCVQZ basis sets are applied to the all-electrons calculations. On this potential energy surface, the triplet oxygen atom attacks methane in a near-collinear H-CH(3)direction to form a saddle point with barrier height of 13.55 kcal/mol, which plays a key role in the kinetics of the title reaction. For the temperature range of 298-2500 K, our calculated thermal rate constants for the O(P-3) + CH4 -> OH + CH(3)reaction show good agreement with relevant experimental data. This work provides detailed mechanism of this gas-phase reaction and a theoretical guidance for methane combustion.