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

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.