The finite-size (6,5) SWCNT was constructed using the visual molecular dynamics (VMD) package 79 including 3 unit cells (∼ 10 nm, 1092 atoms). The edges were properly capped with hydrogens according to previous works. The SWCNT was optimized at the CAM-B3LYP/STO-3G level, followed by the calculation of the 20 lowest-energy vertical excitations at the same level of theory. This functional and basis has been shown to provide the correct excitonic localization and relative energies for these systems. Eq. 4 was solved with 20 electronic states and 5 Fock states.