Low-lying states of FeSiₙ⁻/º/⁺ (n = 1-2) clusters from DMRG-CASPT2 calculations

Abstract

The electronic states of FeSiₙ⁻/º/⁺ (n 1-2) clusters have been investigated with DFT, CASPT2, and DMRG- CASPT2 methods. By using relatively large active spaces, the DMRG-CASPT2 method is found to provide highly accurate relative energies for the various relevant electronic states. Leading configurations, bond distances, harmonic vibrational frequencies, and relative energies for the low-lying states of the title clusters are reported. Electron detachment energies for the ground states of the anionic and neutral clusters were estimated at the DMRG-CASPT2 level. Franck Condon factor simulations were performed for transitions from the anionic ground state to the neutral ground state and from the neutral ground state to the cationic ground state with the purpose to produce the vibrational progressions.