geometries supplied by Sengupta and Raghavachari 1 (some molecules related to R2, R5 and R16 were missing and build from scratch). Enthalpy corrections are not included for the NDDO-based methods, because they are parameterized to reproduce enthalpies of formation. We computed enthalpies of formation, for analysis-purposes, using the method outlined by Curtiss et al. . The PBEh-3c and HF-3c are performed with ORCA , the DFTB calculations with GAMESS , the xTB calculations with the xTB program 11 , the OM2 with MNDO 27 and the remaining NDDO-based methods are performed with in MOPAC .