Ab initio study of the CO–N₂ complex: a new highly accurate intermolecular potential energy surface and rovibrational spectrum

Abstract

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 is characterized by an almost T-shaped structure 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.

Ab initio investigation of the CO–N2 quantum scattering: The collisional perturbation of the pure rotational R(0) line in CO

“…Nonetheless, as it was stated in Ref. 57, due to the method used, reduction of the basis set and too small number of grid points chosen by the authors, this PES should not be considered reliable enough to study various physical phenomena. Recently, three highly accurate PESs were reported.…”

“…53,54 We recall also two very recent studies of this complex in the millimeter range, 55,56 which provided an accurate test of the recently reported PESs. 55,57,58 The theoretical investigations on the CO-N 2 complex were reviewed in more detail in a previous paper. 57 Here, we only recall the importance of the study conducted by Fišer and Polák, 59 who investigated multiple orientations of the complex using the coupled-cluster singles and doubles including connected triple corrections [CCSD(T)] and Møller-Plesset (MP) perturbation theory up to fourth order.…”

“…55,57,58 The theoretical investigations on the CO-N 2 complex were reviewed in more detail in a previous paper. 57 Here, we only recall the importance of the study conducted by Fišer and Polák, 59 who investigated multiple orientations of the complex using the coupled-cluster singles and doubles including connected triple corrections [CCSD(T)] and Møller-Plesset (MP) perturbation theory up to fourth order. The first fourdimensional (4D) PES was reported by Karimi-Jafari et al, 60 who employed the MP4 method with a basis set obtained from the Dunning's aug-cc-pVQZ basis set.…”

“…Recently, three highly accurate PESs were reported. 55,57,58 Liu et al 58 calculated a 5D PES using the CCSD(T)-F12 method and the aug-cc-pVQZ basis set, claiming the discrepancies between theoretical and experimental energies of the IR transitions of the CO-N 2 complex to be smaller than 0.068 cm −1 . Surin et al 55 reported a 4D PES calculated using the standard CCSD(T) method and the aug-cc-pVQZ basis set, supplemented with 3s2p1d midbond functions.…”

Computational study of the ro-vibrational spectrum of CO–CO2

“…It has been demonstrated that such calculations are accurate for other Van der Waals dimers. [11][12][13][14] Probability Density (PD) and wavefunction cut plots are used to label the energy levels. We find significant coupling between in-plane and out-of-plane coordinates.…”