This second-order expression corresponds to the dispersion energy present in SAPT0 [Eq. ( )] As discussed previously, it is typically much too attractive, e.g., by 80-100% for π-stacked benzene dimer. For larger system, errors in second-order perturbation theory are even more egregious. For that reason, we substitute a dispersion model in XSAPT + MBD, which performs extremely well as compared to dispersion energies obtained from SAPT2+(3) calculations, as discussed previously in the context of Fig. . We consider that SAPT2+(3) constitutes a benchmark level of theory for the energy components because total interaction energies computed at that level agree with CCSD(T) results to subkcal/mol accuracy. Good agreement between XSAPT + MBD and SAPT2+(3) energy components thus lends credence to the idea that the former does not benefit significantly from error cancellation, so that individual energy components within the SAPT formalism can be swapped out for better models, e.g., substituting the non-perturbative MBD model for dispersion.