[129] The combination of range separation and large admixture of Fock exchange (RSX-QIDH) and/or secondorder perturbative correlation (ωPBEPP86/ωB88PP86) tends to overbind the benzene excimer with accumulative effects. Notably, ωPBEPP86 contains a proportion of MP2 correlation (48%) greater than the complement of the DFT correlation (32%), defying the usual constraint in semi-empirical optimisation of spin-unscaled double-hybrids where DFT and MP2 coefficients sum to unity. The large MP2-correlation components (42 and 48%) of ωPBEPP86 and ωB88PP86 appear to be the culprit of their overbinding tendency. As spincomponent scaling has shown to reduce the overestimation of dispersion interactions and excitation energies associated with ground and excited state second-order perturbative methods, MP2 and CIS(D) , it is unsurprising that the functionals most improved by spin scaling are those with large second-order perturbation theory components. Some of the dispersion-uncorrected functionals tested predict the benzene excimer binding very close to the reference. As we will explore later, this leaves no room to account for missing dispersion effects via additive dispersion corrections. However, as outlined earlier, dispersion interactions and exciton coupling are less important to the binding of the benzene excimer than in larger excimers.[130] Therefore, the following section explores the larger pyrene excimer as a demonstrative example.