Figure shows the density of states (DOSs) for the orbitals ranging from HOMO-20 to LUMO+10, calculated for [Pt17(CO)12(P(CH3)3)8] 2+ (basis set; SDD for Pt, 6-311 + G* for P, C, O, and H). It was revealed that the orbitals near the HOMO and LUMO primarily comprise the s, p, and d orbitals of Pt (Fig. ). Owing to the high symmetry of [Pt17(CO)12(P(CH3)3)8] 2+ , the transition from HOMO to LUMO is forbidden (Fig. ), and thus it is not observed (at 0.74 eV) in the experimental optical absorption spectrum (Fig. ). The peak around 1.40 eV is attributed to transitions from HOMO-1,2,3,4 to LUMO or LUMO+1, whereas the peak near 1.55 eV is due to transitions from HOMO-5 to LUMO+1. The peak around 2.10 eV involves multiple transitions, including those from orbitals below HOMO-10 to LUMO, as well as transitions from orbitals near HOMO to LUMO+1 and the orbitals above. Further analysis using the LANL2DZ basis set confirmed that the DOSs of [Pt17(CO)12(PPh3)8] 2+ are not significantly influenced by the choice of basis set nor functional group substitutions (Fig. ).