Explicit correlation treatment of the potential energy surface of CO₂ dimer

We present an extensive study of the four-dimensional potential energy surface (4D-PES) of the carbon dioxide dimer, (CO₂)₂. This PES is developed over the set of intermolecular coordinates. The electronic computations are carried out at the explicitly correlated coupled cluster method with single, double, and perturbative triple excitations [CCSD(T)-F12] level of theory in connection with the augmented correlation-consistent aug-cc-pVTZ basis set. An analytic representation of the 4D-PES is derived. Our extensive calculations confirm that “Slipped Parallel” is the most stable form and that the T-shaped structure corresponds to a transition state. Later on, this PES is employed for the calculations of the vibrational energy levels of the dimer. Moreover, the temperature dependence of the dimer second virial coefficient and of the first spectral moment of rototranslational collision-induced absorption spectrum is derived. For both quantities, a good agreement is found between our values and the experimental data for a wide range of temperatures. This attests to the high quality of our PES. Generally, our PES and results can be used for modeling CO₂ supercritical fluidity and examination of its role in planetary atmospheres. It can be also incorporated into dynamical computations of CO₂ capture and sequestration. This allows deep understanding, at the microscopic level, of these processes