We have already mentioned problems in state order for the naphthalene and pyrene dimers in Sections 4.2.2 and 4.2.4, but still need to elaborate more in detail on the fact that the dimers consist of polycyclic aromatic hydrocarbons (PAHs). Singlemolecule studies of PAHs have established that the first two π-π * excitations in PAHs-called L a and L b according to Platt 201 -are poorly described by many TD-DFT methods, including global hybrids. RS hybrids can improve the description of L a but blueshift L b excitations. Double hybrids, particularly the latest range-separated ones, have to date yielded the most accurate and balanced description of both states in PAHs. This, in addition to the aforementioned better description of exciton coupling, Its various dispersion-corrected variants all depend on slightly different underlying XC expressions, which is why dispersion-corrected results are not provided.