that is proportional to the number of electron N e in the system and consequently cancels out between the energies of the dimer and monomers. Therefore, although beneficial for total energies, the BAP scheme does not improve the convergence of HF interaction energies for both cubic and orthorhombic boxes, and necessitates large volumes to recover the last fraction of the mean field energy. Moreover, although a cubic box expansion with BAP accelerates the MP2c convergence against Φ(0) = 0 (Fig. ), the BAP correction with an orthorhombic box makes it converge more slowly and nonmonotonically. This is a consequence of the BAP singularity correction (Eq.15) that may switch sign depending on if the repulsion between the repeated Gaussian charge images or their attraction with the compensating background dominates according to the elongation of the cell . This demonstrates that the convergence behavior of the MP2 correlation energy for various supercell sizes and symmetries is non-trivial when resorting to effective Coulomb potentials.