A benchmark quantum chemical study of the stacking interaction between larger polycondensed aromatic hydrocarbons

Large-scale electronic structure calculations were performed for the interaction energy between coronene, C₂₄H₁₂ with circumcoronene, C₅₄H₁₈, and between two circumcoronene molecules, in order to get a picture of the interaction between larger graphene sheets. Most calculations were performed at the SCS-MP2 level but we have corrected them for higher-order correlation effects using a calculation on the coronene-circumcoronene system at the quadratic CI, QCISD(T) level. Our best estimate for the interaction energy between coronene and circumcoronene is 32.1?kcal/mol. We estimate the binding of coronene on a graphite surface to be 37.4 or 1.56?kcal/mol per carbon atom (67.5?meV/C atom). This is also our estimate for the exfoliation energy of graphite. It is higher than most previous theoretical estimates. The SCS-MP2 method which reproduces the CCSD(T) and QCISD(T) values very well for smaller aromatic hydrocarbons, e.g., for the benzene dimer, increasingly overestimates dispersion as the bandgap (the HOMO-LUMO separation) decreases. The barrier to the sliding motion of coronene on circumcoronene is 0.45?kcal/mol, and for two circumcoronene molecules 1.85?kcal/mol (0.018 and 0.034?kcal/mol per C atom, respectively). This means that larger graphenes cannot easily glide over each other.