Electron Detachments of NbSin-/0 (n=1-3) Clusters from Density Matrix Renormalization Group-CASPT2 Calculations

The electronic states of NbSin-/0/+ (n = 1-3) clusters have been explored using the state-of-the-art DMRG-CASPT2 method with relatively large active spaces. The leading configurations, bond distances, vibrational frequencies, and relative energies of the low-lying states were identified. Electron detachment energies of the anionic cluster and ionization energies of the neutral clusters were reported at the DMRG-CASPT2 level. The ground states of the NbSin-/0/+ (n = 1-3) clusters were predicted as the 3 Delta, 4 pi, and 5 pi states of the linear NbSi-/0/+, the 3A2, 4B1, and 3B1 states of cyclic NbSi2-/0/+, and the 1A ', 2A ', and 3A '' states of tetrahedral NbSi3 -/0/+ isomers. The first feature in the photoelectron spectrum of NbSi- was attributed to the transitions from the anionic 3 Delta ground state to the neutral 4 pi, 4 Delta, and 4 phi states, whereas the second feature was assigned to the transitions to the neutral 2 Delta, 2 sigma+, and 2 phi states. The first band in the photoelectron spectrum of NbSi3- was ascribed to the transition from the anionic 1A ' ground state to the neutral 12A ' and 12A '' states; the second band was attributed to the transitions to 22A ', 22A '', and 32A ' states; and the third band was assigned to the transition to 32A ' states.