Classical trajectory study of the dynamics of the reaction of Cl atoms with ethane.

We present an electronic-structure and dynamics study of the Cl + C2H6 --> HCl + C2H5 reaction. The stationary points of the ground-state potential energy surface have been characterized using various electronic-structure methods and basis sets. Our best calculations, CCSD(T) extrapolated to the complete basis limit, using geometries and harmonic frequencies obtained at the MP2/aug-cc-pVTZ level, are in agreement with the experimental reaction energy. Ab initio information has been used to reparameterize a semiempirical Hamiltonian so that the predictions of the improved Hamiltonian agree with the higher-level calculations in key regions of the potential energy surface. The improved semiempirical Hamiltonian is then used to propagate quasiclassical trajectories. Computed kinetic energy release and scattering angle distributions at a collision energy of approximately 5.5 kcal mol(-1) are in reasonable agreement with experiments, but no evidence was found for the low translational energy HCl products scattered in the backward hemisphere reported in recent experiments.