The effect of E ρ ia cut on the correlation energy is reported in Table which shows that no difference greater than 0.01 kcal/mol results from reducing E ρ ia cut to the wavefunction cutoff energy E ϕ cut (150 Ry) for various systems and supercell volumes. This amounts to projecting the pair densities, which require less high-frequency components, onto an auxiliary basis set for efficient computation of integrals, similar to what is done for example in the resolution-of-identity with GTO approaches (e.g. RI-MP2) . We strongly emphasize the great benefit of such a reduction; in the case of e.g. the paralleldisplaced (PD) benzene dimer, computing the MP2 energies with E ρ ia cut = 600 Ry is simply impossible on 25 nodes with 128GB of memory each, while all test systems reported below could be evaluated with such a setup by fixing E ρ ia cut to 150 Ry from now on.