Indeed, direct comparison of SAPT0(KS) methods with different XC functionals demonstrates that SAPT0(B3LYP) is considerably less accurate than SAPT0(HF), despite the incorporation of monomer electron correlation. This is demonstrated in Table using the S66 data set. For the dispersion-bound subset of S66, SAPT0(B3LYP) exhibits a maximum error of 4.5 kcal/mol versus only 1.5 kcal/mol for conventional SAPT0(HF), and the B3LYP-based approach is also less accurate for hydrogen-bonded systems, where monomer correlation is known to be important. Errors for the SAPT0(BLYP) approach are larger still, as the lack of any exact exchange whatsoever leads to worse asymptotic behavior as compared to B3LYP, and further exaggeration of dispersion energies as a result. In contrast, the SAPT0(LRC-ω GDD PBE) approach reduces the maximum error for the dispersion-bound complexes to 2.0 kcal/mol, although this method remains less accurate than SAPT0(HF) for each of the standard subsets of S66. The final two sets of XSAPT calculations in Table use electrostatic embedding charges that are discussed in Section 1.2.3, and dispersion models that are discussed in Section 1.2.4. Once those aspects of the formalism have been described, we will present a more complete compendium of accuracy assessments in Section 2.1.