Assessment of density functional approximations for N₂ and CO₂ physisorption on benzene and graphene

Experimental isotherms of N₂ and CO₂ on carbon-based porous materials and models of the physisorption of gases on surfaces are used to obtain the pore size distribution (PSD). An accurate modelization of the physisorption of N₂ and CO₂ on the surface of carbon-based porous materials is important to obtain accurate N₂ and CO₂ storage capacities and reliable PSDs. Physisorption depends on the dispersion interactions. High precision ab initio methods, such as CCSD(T), consider accurately the dispersion interactions, but they are computationally expensive. Double hybrid, hybrid and DFT-based methods are much less expensive. In the case of graphene, there are experimental data of the adsorption of N₂ and CO₂ on graphite that can be used to build the Steele interaction potential of these gases on graphene. The goal is to find out hybrid and/or DFT methods that are as accurate as the CCSD(T) on benzene and as accurate as the experimental results on graphene. Calculations of the interaction energy curves of N₂ and CO₂ on benzene and graphene have been carried out using the CCSD(T) method and several double hybrid, hybrid, and DFT methods that consider the dispersion interactions. The energy curves on benzene have been compared to the CCSD(T) and the energy curves on graphene have been compared with the Steele energy curves. The comparisons indicate that double hybrids with dispersion corrections and ωB97 based DFT methods are accurate enough for benzene. For graphene, only the PBE-XDM functional has a good agreement with the Steele energy curves.