Potential energy surface of the CO2–N2 van der Waals complex

Abstract

Four-dimensional potential energy surface (4D-PES) of the atmospherically relevant CO2-N2 van der Waals complex is generated using the explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in conjunction with the augmented correlation consistent triple zeta (aug-cc-pVTZ) basis set. This 4D-PES is mapped along the intermonomer coordinates. An analytic fit of this 4D-PES is performed. Our extensive computations confirm that the most stable form corresponds to a T-shape structure where the nitrogen molecule points towards the carbon atom of CO2. In addition, we located a second isomer and two transition states in the ground state PES of CO2-N2. All of them lay below the CO2 + N2 dissociation limit. This 4D-PES is flat and strongly anisotropic along the intermonomer coordinates. This results in the possibility of the occurrence of large amplitude motions within the complex, such as the inversion of N2, as suggested in the recent spectroscopic experiments. Finally, we show that the experimentally established deviations from the C2v structure at equilibrium for the most stable isomer are due to the zero-point out-of-plane vibration correction.

Ab initio intermolecular potential energy surface for the CO2—N2 system and related thermophysical properties

“…2) with interaction energies of −228.77 K (θ 1 = 0 • , θ 2 = 90 • ) and −475.76 K (θ 1 = 90 • , θ 2 = 0 • ). This is in agreement with the findings of Nasri et al, 18 who performed supermolecular CCSD(T)-F12a 34 /aug-cc-pVTZ calculations, both for the case that all degrees of freedom are relaxed and for the case that rigid equilibrium structures of the two monomers are used to identify the two minima. Since we used zero-point vibrationally averaged monomer geometries in the present work, small differences when comparing the results are to be expected.…”

“…5,6 Hence, only a CO 2 -N 2 potential of similar quality needed to be developed. A literature search indicated that in 2015 Nasri et al 18 developed a CO 2 -N 2 pair potential of comparable quality; however, their paper does not provide the details necessary to reproduce the PES, and the attempts by the present authors to obtain these details were unsuccessful.…”

Communication: Spectroscopic observation of the O-bonded T-shaped isomer of the CO-CO2 dimer and two of its intermolecular frequencies

“…Because measurements of these low-frequency intermolecular modes provide a means to probe potential surfaces at a high level of precision, we conclude that the published ab initio results are inadequate in predicting these frequencies and therefore call for modern high-level ab initio calculations which explore the complete intermolecular potential surface with results relevant to highresolution spectroscopy. Naturally, studies of the isoelectronic dimer CO 2 -N 2 , both experimental 12,13 and theoretical, 14 are also relevant in the present context.…”

Energy transfer dynamics and kinetics of elementary processes (promoted) by gas‐phase CO2‐N2 collisions: Selectivity control by the anisotropy of the interaction

“…In principle, intermolecular potentials can be characterized by both molecular beam scattering experiments (see, e.g., [8] ) and spectroscopic studies of van der Waals complexes. [9] Yet, the inversion of these measured data is neither easy nor direct. One should be able, in fact, to carry out the experiment under high resolution conditions, to make an educated guess of the value of the parameters of a model potential and then refine it by minimizing the difference between theoretical and experimental results.…”

“…For this reason dimer PESs available in the literature, that consider frozen monomers, while allowing the reproduction of spectroscopic properties of the dimers and virial coefficients, [10,11] are not suited for modeling the energy transfer. [9] For example, the intermolecular PES for CO 2 1 N 2 should be a nine-dimensional PES. For the same reason energy transfer in kinetic studies would be better dealt at a state-to-state level of detail by determining state-to-state rate coefficients (see, e.g., [12][13][14] for state-to-state kinetic models of gaseous systems).…”