In the calculation of fragments, either the basis functions carried by the fragment atoms (monomer basis, MB) or those carried by all atoms in the entire system (complex basis, CB) may be used. The latter is evidently more expensive and hence MB is suggested to be used by default; however, as will be shown later, the use of CB is important for reliably studying intermolecular weak interactions, especially when the basis set is not diffuse enough. When CB is used instead of MB, the total interaction energy derived by sobEDA is equal to the counterpoise corrected interaction energy, that is ∆𝐸𝐸 int = 𝐸𝐸 complex (CB) -∑ 𝐸𝐸 𝐴𝐴 (CB)