However, for systems such as (C 96 H 24 ) 2 , which is a nanoscale model of π-stacking in graphene, the "loose/normal" (L/N) MP2 extrapolation procedure (requiring only T CutPNO ≥ 10 -8 ) is insufficient to obtain benchmark-quality results, affording a DLPNO error of 5 kcal/mol. For this system, a "normal/tight" (N/T) MP2 extrapolation (requiring T CutPNO = 10 -9 ) must be used instead, if the DLPNO error is to be reduced below 1 kcal/mol or about 0.5% of |∆E|.