Theoretical characterization of the minimum energy path for hydrogen atom addition to N2: Implications for the unimolecular lifetime of HN2

Abstract

The minimum energy path (MEP) for the addition of a hydrogen atom to N2 is characterized in CASSCF/externally contracted CI calculations using a [4s3p2d1f/3s2p1d] ANO basis set, with additional single point calculations at the stationary points of the potential energy surface using a [5s4p3d2f/4s3p2s] ANO basis set. These calculations represent the most extensive set of ab initio calculations on HN2 completed to date, yielding a zero-point corrected barrier for HN2 dissociation of ≊8.5 kcal mol−1. The lifetime of the HN2 species is estimated from the calculated geometries and energetics using both conventional transition state theory and a method which utilizes an Eckart barrier to compute one-dimensional quantum mechanical tunneling effects. This study concludes that the lifetime of the HN2 species is very short, greatly limiting its role in combustion processes.