Comparatively, the KPCA procedure demonstrated an intrinsic ability to recognize structural similarity between symmetry-related conformations. However, it was unable to differentiate a pair of clusters that were expected to be separated based on our preliminary knowledge of the system and visual inspection. Specifically, the two combined clusters correspond to the excimer conformations in which the pyrene molecules are shifted along the stacking coordinate and twisted by 49 and 79 degrees, respectively (3.1 and 3.2 in Figure ; see also Table ). However, this issue could be easily resolved by sub-clustering the initially defined cluster (see Fig. ). On the other hand, the RMSD approach is undoubtedly capable of capturing very subtle geometric discrepancies, albeit at the cost of introducing a stricter differentiation in some areas of the conformational space. This is evident among the pair of T-shaped structures in cluster 9; some detectable structural differences do not translate in the same way into different electronic features.