Fig. also shows parts of the dissociation curves of the three truncated basis set levels for SCS-CC2. We can clearly rule out the DZ level from further consideration. The TZ and QZ curves are relatively close to one another with the difference between both their minima being only 0.11 kcal/mol, suggesting the result is close to convergence (Table † ). The SCS-CC2/def2-TZVP minimum lies 0.34 kcal/mol above the CCSDR(3)/CBS interaction energy at r = 3.00 Å. In contrast, the SCS-CC2/def2-QZVP mimimim is only 0.23 kcal/mol higher. Considering that the CCSDR(3)/CBS interaction energy at r = 3.00 Å is -13.52 kcal/mol, the percentage errors for the SCS-CC2/TZ, QZ and CBS (3,4) minima are only 2.5, 1.7 and 0.96%, respectively; see Table for the SCS-CC2/CBS (3,4) minimum.