Anchoring the potential energy surface of the nitrogen/water dimer, N2⋯H2O, with explicitly correlated coupled-cluster computations

- Energetics of nitrogen/water dimer characterized at the CCSD(T) complete basis set (CBS) limit.
- Three transition states have been identified that lie 0.51-0.61 kcal mol−1 above the global minimum at the CCSD(T) CBS limit.
- Resolved discrepancy over identity of global minimum with CCSD(T) computations and basis sets as large as aug-cc-pVQZ.
- IR activity of OH stretching vibrations increases substantially upon dimerization within double harmonic approximation.

Six different stationary points have been identified and characterized on the potential energy surface of N2⋯H2O (i.e., the non-covalent dimer formed between nitrogen and water). Optimized geometries and harmonic vibrational frequencies have been computed using the MP2 and CCSD(T) ab initio electronic structure methods in conjunction with a series of correlation consistent basis sets as large as aug-cc-pVQZ. In addition, explicitly correlated CCSD(T)-F12 single point energy computations in conjunction with basis sets as large as aug-cc-pV5Z have been used to estimate the relative energetics at the complete basis set (CBS) limit. Only one configuration corresponds to a minimum, a Cs structure with an O-H⋯N interaction and an electronic dissociation energy of 1.22 kcal mol−1 at the CCSD(T) CBS limit. CCSD(T) harmonic vibrational frequency computations indicate that the IR intensities of the OH stretching modes increase substantially when the dimer forms. Three transition states lie 0.51-0.61 kcal mol−1 above the global minimum at the CCSD(T) CBS limit, which indicates that the barriers associated with rearrangement pathways are comparable to those for (H2O)2.

A single minimum on the nitrogen/water dimer potential energy surface has been identified with an electronic dissociation energy of 1.22 kcal mol−1 at the CCSD(T) complete basis set limit.