Low-lying states of FeSin −/0/+ (n = 1-2) clusters from DMRG-CASPT2 calculations

The electronic states of FeSin −/0/+ (n = 1-2) clusters have been investigated with DFT, CASPT2, and DMRGCASPT2 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.