In subsequent generations of the model, parameters were fit so that the model dispersion energy E aiD disp reproduces ab initio dispersion energies obtained from third-order calculations such as SAPT2+(3). The most recent ai D3 version 37 uses an improved training set and is the recommend version. Unlike ai D1, these models offer consistent accuracy for E int and each of its individual components, indicating that the total does not benefit from error cancellation so the energy components ought to be reliable. As shown in Fig. using the S66 data set, the accuracy of XSAPT + ai D3 (which includes charge embedding) is competitive with a variety of post-SCF methods including SAPT2+( mean absolute error (MAE) less than 0.3 kcal/mol. Nevertheless, the performance of the atomic pairwise dispersion approximation in Eq. ( ) breaks down for large molecules, degrading the performance of XSAPT + ai D and any similar SAPT + D model when the monomers are large. This can be seen in benchmark tests on the L7 data set, 132 which consists of larger complexes with up to 73 second-row atoms (Fig. ). Errors obtained using XSAPT + ai D3 are much larger for L7 (up to 5 kcal/mol) as compared to those for the small S66 dimers, and a variety of dispersion-inclusive and dispersion-corrected DFT approaches are significantly more accurate. At the other end of the spectrum, MP2/CBS significantly overestimates dispersion energies for dimers involving highly conjugated molecules, such as coronene and circumcoronene in L7. The only MP2-based method with reasonable accurate for this data set is "attenuated" (att-)MP2, 133 which removes the long-range portion of the Coulomb operator from the post-SCF calculation, and whose success for noncovalent interactions likely rests on error cancellation.