VARIATIONAL STATISTICAL STUDY OF THE CN+O2 REACTION EMPLOYING AB-INITIO DETERMINED PROPERTIES FOR THE TRANSITION-STATE

A combination of ab initio electronic structure and variational statistical calculations are employed in a study of the kinetics of the CN+O2 reaction. Interaction energies for the transition state region of the CN+O2 reaction are evaluated within a multiconfiguration self-consistent field framework. Optimized geometries and force fields are determined for six fixed CO separation distances (R(CO)) ranging from 1.7 to 3.0 angstrom and for the NCOO complex. The optimized NCO and COO bending angles are generally near 180-degrees and 115-degrees, respectively. A model analytical potential is fit to the ab initio data. This model potential is then used in variational statistical evaluations of the rate of complex formation employing a bond length reaction coordinate. A comparison between theoretical and experimental results indicates the importance of considering the deviations of the electronic interactions from those predicted by long-range expansions. In particular, variational statistical calculations employing a realistic potential energy surface which fully incorporates the short-range interactions are in quantitative agreement with the experimental data for temperatures ranging from 50 to 3000 K.