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. | Cite this paper Vietnam J. Chem. 2023 61 1 43-51 Research article DOI Low-lying states of FeSin 0 n 1-2 clusters from DMRG-CASPT2 calculations Tran Van Tan1 Tran Quoc Tri1 Phan Trung Cang1 Nguyen Thi Hong Hanh1 Ho Sy Linh1 Nguyen Phu Tan1 Marc . Hendrickx2 1 Theoretical and Physical Chemistry Division Dong Thap University 783-Pham Huu Lau Ward 6 Cao Lanh City Dong Thap 81000 Viet Nam 2 Quantum chemistry and Physical Chemistry Division Chemistry Department Katholieke Universiteit Leuven Celestijnenlaan 200F B-3001 Heverlee-Leuven Belgium Submitted April 7 2022 Revised August 26 2022 Accepted September 14 2022 Abstract The electronic states of FeSin 0 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. Keywords. DMRG-CASPT2 detachment energy relative energy Franck-Condon factors vibrational frequency. 1. INTRODUCTION investigated by the CASSCF and MRSDCI methods. 13 The ground state of the neutral cluster The structures and properties of many transition was predicted to be a 3Δ with a 5Π at eV. Bond metal-doped silicon clusters were studied by distances vibrational frequencies electron affinities experimental and quantum chemical methods in the ionization potentials dissociation energies and search for stable structures that can be .
