Binding energy per carbon atom in the cluster for some neutral homo-molecular PAH clusters. Red filled circles are for dimers, black open circles for larger clusters with 3 to 12 molecules. The binding energy per carbon atom increases with the size of monomers and with the number of molecules in the cluster. The blue curve is the empirical relation determined by Herdman & Miller (2008) and shows a maximum relative difference of 7% with our results. The structures of the three monomers considered in this study, coronene C₂₄H₁₂, circumcoronene C₅₄H₁₈, and circumcircumcoronene C₉₆H₂₄, are also shown.