Ab Initio Study of the CO–N2 Complex: a New Highly Accurate Intermolecular Potential Energy Surface and Rovibrational Spectrum
Carrington, Tucker Jr
Intermolecular Potential-Energy Surface
A new, highly accurate ab initio ground-state intermolecular potential-energy surface (IPES) for the CO-N2 complex is presented. Thousands of interaction energies calculated with the CCSD(T) method and Dunning’s aug-cc-pVQZ basis set extended with midbond functions were ﬁtted to an analytical function. The global minimum of the potential corresponds to the geometry characterized by r0 = 7.856a0, θ1 = 111.3◦, θ2 = 159.7◦, and φ2 = 0◦ and has an energy of −118.2 cm−1. The symmetry-adapted Lanczos algorithm was used to compute rovibrational energies (up to J = 20) on the new IPES. The RMSE with respect to experiment was found to be on the order of 0.038 cm−1 which conﬁrms the very high accuracy of the potential. This level of agreement is among the best reported in the literature for weakly bound systems and considerably improves on those of previously published potentials.