(2) disp (FCI) as the reference. In the the Fig. we have plotted the percent difference of the dispersion energy in with respect to the FCI dispersion, as a function of interatomic separation (except E (20) disp which performs significantly worse). One might notice that DF-CCSD(4) dispersion of Korona and Jeziorski recovers the FCI dispersion almost exactly (see also discussions in Ref. ), since polarization propagator in CCSD(4) approximation is nearly exact for two electron system. The CCPP2 dispersion energy is very closely follows CCD+ST(CCD) method: both methods reproduce the SAPT interaction energies up to 2nd order in the intramonomer correlation and include summation of some classes of diagrams to infinity. Such summation is important: both methods perform significantly better than "bare" SAPT up to E (22) disp , and significantly outperform the dispersion from TDHF and TDDFT (PBE0) methods. As the distance increases for all methods reported, except TDDFT the accuracy slightly worsen, but for CCPP2(T) is always below 2%.