A number of issues were observed with the ShaMan model. Firstly, comparison to the literature is difficult; Manian and co-worker's study on perylene's incorrectly mapped excited state manifolds . Secondly, it is clear from these results that density functional theory is drastically overestimating the vibronic coupling between two excited states. Density functional theory is formally exact with respect to the density functional approximation used ; therefore, any failures are part of the functional rather than the method itself . Consequentially, density functional theory may not be a viable method to calculate vibronic coupling between two excited states until either a new functional is design to cater specifically to this problem, or until there is an exact solution for the density functional approximation; however, the latter is unlikely to occur in the foreseeable future . Conversely, one could use multi-reference methods to calculate the couplings, however not only is this exceedingly resource intensive, rates were still shown to fall short likely due to the lack of solvent effects.