However, the major reason for overbinding should be connected with basis set superposition effects (BSSE). In the expansion used for the 2-body approach, this effect is not accounted for, and even if it only contributes with a small error < 1 kJ•mol -1 per dimer, this value will add up with increasing number of pairs. In general, we observe stronger overestimations for smaller monomers and/or hydrogen-bonded systems. One further evidence to this fact is the change in MAD (to plane-wave values) between def-TZVP and def2-QZVPP results (15.3 kJ•mol -1 and 9.9 kJ•mol -1 , respectively). We have, however, opted to not include counterpoise corrections. In part, because we deem such corrections tend to overestimate the effect. Secondly, this would make the procedure prohibitive in terms of computational costs.