2.31 eV in case of coronene. The reaction pathways on the PES connecting ground and defected states are schematically depicted in Fig. \[trans\_scheme.fig\] for the two neutral molecules pyrene and coronene. In case of pyrene we do not observe a Stone-Wales transition leading to the Stone-Wales defect, but a more complicated path via two vastly nonplanar transition states (TS1 and TS2 in Figs. \[trans\_scheme.fig\] and \[Entstehung.fig\]) and a shallow local minimum (LM) configuration in between (LM in Figs. \[trans\_scheme.fig\] and \[Entstehung.fig\]) that does almost not differ from the two transition structures, see Fig. \[Entstehung.fig\]. To find this pathway it has been necessary to replace the usual 6-31G(2df,p) basis set (Ditchfield et al. [@ditch]) used in G4(MP2) theory by the a bit larger cc-pVTZ basis set, because with the former one it has not been possible to achieve convergence for the local minimum structure. Furthermore, it turns out that the geometry that is achieved when the central C-C bond in pyrene is just rotated by 45 degrees corresponds to a transition structure of second order exhibiting two imaginary frequencies. In case of coronene we observe that the transition between the ground and defected state actually proceeds via the Stone-Wales transition, however, 