A possible explanation for that can be found by analyzing the absolute energy of the valence orbitals of gold (Table ). We notice that by going from PBE0 to RSX-PBE0, the The UV/vis photo-absorption spectrum of a noble metal nanocluster is not only influenced by the size of the system but also by its shape. Figure depicts the influence of the latter parameter on the spectroscopic properties of gold nanoclusters in icosahedral (I h ) symmetry. More precisely, it focuses on Au 5+ 13 , Au 5+ 55 and Au - 147 for which the size is evaluated as 0.55, 1.10 and 1.64 nm, respectively. At first look, the spectral signature of this type of structure is more difficult to analyze. Here, the plasmon resonance is indeed much more delocalized and leads to a breaking of the excitation degeneracy. However, for structures sufficiently large like Au - 147 , the emergence of isolated plasmon bands starts to be more easily detected, notably at RSX-PBE0 level.