BSSE is essentially a form of charge transfer between neighboring atoms, which grows with system size because so does the number of neighbors (meaning nearby pairs of atoms). This form of extensivity is illustrated in Table , which quantifies the BSSE for sizable vdW complexes in various basis sets. Here, BSSE is defined as The complexes in Table include the coronene dimer, (C 24 H 12 ) 2 , and several trimers involving layered materials in which a graphene nanoribbon such as C 59 H 20 is sandwiched between polythiophene oligomers, (pT) n . Each of these layered composites exceeds 100 atoms and the BSSE computed at the ωB97M-V/def2-SVPD level exceeds 30 kcal/mol, approaching 50 kcal/mol for the largest example. This is 10-20× larger than the BSSE for any of the S66 complexes at the same level of theory. For (C 24 H 12 ) 2 , the BSSE is reduced below 1 kcal/mol when def2-TZVPD is used, but that is not true for the larger complexes considered in Table . In those cases, residual BSSE of about 3 kcal/mol persists in the def2-TZVPD basis set. For large vdW complexes, where basis sets beyond double-ζ quality may not be feasible, CP correction is critically important in order to obtain results that are even qualitatively reasonable. In addition, CP correction can partially mitigate the need for diffuse basis functions.