AB-INITIO VARIATIONAL TRANSITION-STATE THEORY CALCULATIONS FOR THE O+NH2 HYDROGEN ABSTRACTION REACTION ON THE 4A' AND 4A'' POTENTIAL-ENERGY SURFACES

We report high level ab initio calculations that characterize the quartet potential energy surfaces 4A″ and 4A′ for the O+NH2 direct hydrogen abstraction reaction. Minimum energy reaction pathways have been computed on both surfaces at the full-valence complete active space self-consistent field level using a correlation consistent polarized valence double zeta basis set. Energies along these reaction pathways have been further refined by multireference configuration interaction calculations with a correlation-consistent polarized valence triple zeta basis set. Canonical variational transition state theory calculations using the ab initio potential energy surface information as input and incorporating tunneling through the ground state vibrationally adiabatic potential energy curves indicate that below about 2000 K, the O+NH2 reaction is dominated by addition/(isomerization)/ dissociation pathways, and for temperatures below about 1000 K, even the OH+NH product channel is dominated by the addition/isomerization/dissociation route. © 1995 American Institute of Physics.