Theoretical investigation of the N₂O₅⇌NO₂+NO₃ equilibrium by density functional theory and ab initio calculations

Equilibrium geometries and transition states for the equilibrium N₂O₅⇌NO₂+NO₃ (1) and for the reaction NO₂+NO₃→NO+O₂+NO₂ (2) have been optimised in B3LYP/6-311G* and MP2/6-311G* calculations. The optimised geometries for N₂O₅ are in good agreement with experiment and previous calculations in the literature. A transition state for the decomposition of N₂O₅ has been located. Reaction (2) proceeds via a complex mechanism. The first step is the formation of a peroxy intermediate ONO···ONO₂ that can rearrange via a high lying intermediate to ON(O₂)···ONO, which can then yield NO₂+NO+O₂.