A DMRG-CASPT2 investigation on the electronic states of NiSin−/0/+ (n = 1–3) clusters

Abstract

The electronic states of NiSin−/0/+ (n = 1–3) clusters were studied using the DFT, RASPT2, and DMRG-CASPT2 methods. The DMRG-CASPT2 approach increases the complete active space to 18, 20, and 23 orbitals for NiSin−/0/+ (n = 1–3) clusters to attain accurate energies. The leading configurations, bond distances, vibrational frequencies, and relative energies of the electronic states of NiSin−/0/+ (n = 1–3) clusters are presented. The electron detachment energies of the anionic and neutral clusters are determined. The simulation of the Franck-Condon factors for the transition from the anionic to the neutral ground state within the NiSi3−/0 clusters reveals intense vibrational progressions.