A multifacet mechanism for the OH+HNO₃ reaction: An ab initio molecular orbital/statistical theory study

Ab initio molecular orbital calculations at the G2M(cc3) level of theory were used to study the mechanism for the OH+HNO₃ reaction. Intrinsic reaction coordinate analyses was used to find and confirm four complexes and four transition states. Six membered ring complex formed by hydrogen bonding of HNO₃ with OH radical was found to be stable by 8.1Kcal/mol. Insignificant to atmospheric chemistry, direct abstraction process producing H₂O₂ and NO₂ was predicted to have a barrier of 24.4 Kcal/mol. Below room temperature reaction was found to have strong pressure and tunneling effects. Below room temperature, the rate constants for the decay of OH and OD (in OD+DNO₃) evaluated by kinetic mode.