Molecular complexes of nitric acid with N2: a post Hartree–Fock quantum mechanical study

The structure of the molecular 1:1 complexes of nitric acid with N2 were optimized at the MP2/6-311G(df,pd) level of theory revealed a nearly linear planar O-H…N hydrogen bonded form and a nonplanar and non-hydrogen bonded form. The global minimum energy structure corresponds to a hydrogen-bonded species: −1.31 kcal/mol at the MP4(SDTQ)/6-311+G(df,pd)//MP2/6-311G(df,pd) and −1.27 kcal/mol at the CCSD[T] and QCISD[T]/6-311+G(df,pd)//MP2/6-311G(df,pd) levels. The nonplanar form is predicted to be a very weakly bonded system at both the MP4(SDTQ)/6-311+G(df,pd)//MP2/6-311G(df,pd) (−0.34 kcal/mol) and at the CCSD[T]/6-311+G(df,pd)//MP2/6-311G(df,pd) (−0.17 kcal/mol) levels of theory. Additionally, a decomposition of the SCF interaction energy was performed.