Exploring the low‐lying states of CrBn−/0/+ (n = 1–3) clusters using DMRG‐CASPT2 method

This study utilized the DFT, CASPT2, RASPT2, and DMRG‐CASPT2 methods to investigate the low‐lying states of CrB n −/0/+ ( n = 1–3) clusters. The ground states of CrB −/0/+ clusters were identified as 5 Π, 6 Σ + , and 7 Σ + states, while the ground states of CrB 2 −/0/+ clusters corresponded to 4 B 1 , 3 A 2 , and 2 A 2 states of cyclic isomers. Additionally, the ground states of CrB 3 −/0/+ clusters consisted of the 5 B 2 and 6 A 1 states of rhombic‐CrB 3 −/0 isomers, along with the 5 A′ state of the tetrahedral‐CrB 3 + isomer. The results indicated a substantial increase in both electron detachment energies and ionization energies during the transition from CrB −/0 clusters to CrB 2 −/0 clusters, with only slight changes observed in the transition from CrB 2 −/0 clusters to CrB 3 −/0 clusters. Notably, Franck–Condon factor simulations demonstrated vibrational progression in all the transitions from the anionic ground states to the neutral ground states.