The naphthalene excimer is more than twice as stable as the benzene excimer, yielding a SCS-CC2/CBS (3,4) dissociation energy of 28.32 kcal/mol at 3.04 Å (Fig. ). When assessing DFA dissociation energies, one has to consider the well-documented issue of conventional TD-DFT methods often struggling to correctly order the first two excited states of the naphthalene monomer. For instance, TD-B3LYP and TD-BHLYP incorrectly predict the 1 L a state of the monomer to be lower than the 1 L b state. In the fully-stacked dimer, the first excimer state has, in fact, 1 L a character, but at the dissociation limit this turns out to be the second excited state. Indeed, we observe this for our reference method and most other methods, but want to point out that the aforementioned problem for the naphthalene monomer is also observed here, which can lead to the incorrect calculation of dissociation energies for B3LYP and BHLYP if this problem is not spotted. This is particularly a problem when a calculation is carried out without any symmetry, but less so if the programs used distinguish between excited-state symmetries, as the symmetries of the first two excited states differ.