The dynamics of the O(3P) + CH4 reaction has been studied using the quasiclassical trajectory method in conjunction with direct dynamics electronic structure calculations. Several electronic structure methods were used, including DFT (B3LYP/6-31G*) and semiempirical (PM3 and MSINDO) methods. In addition, a recently developed analytical surface (PES) was considered. Our calculations have emphasized collision energies of 1-5 eV because of the importance of this energy range in low Earth orbit research. Our calculated cross sections show that at high energies the H elimination channel yielding H + OCH3 is favored over the lowest barrier product (OH + CH3). Analysis of product energy disposal shows OH and CH3 products that are fairly cold, with most of the energy released to translation. On the other hand, OCH3 carries away most of the energy released to the H + OCH3 products. Angular distributions for OH + CH3 are mainly forward scattered, with a shift from sideways to forward as energy is increased. H + OCH3 is predominantly backward scattered (i.e., the H atom scatters forward). Opacity functions reveal a high selectivity toward OH + CH3 for high impact parameters whereas the H + OCH3 channel is dominant at low impact parameters. MSINDO results compare quite well with more accurate B3LYP/6-31G* calculations, noticeably improving over PM3 for most of the dynamics properties studied.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry