A Multireference Perturbation Theory Study on the Fe₂ molecule: in quest of the ground state.

Renzo Cimiraglia (1) , Celestino Angeli (1)

1 Dipartimento di Chimica

The ⁹Σ^-_g and ⁷Δ_u states of the iron dimer, which according to a long-standing debate are the most probable candidates for the assignment of the ground state, have been investigated within the frame of multireference perturbation theory (PC-NEVPT2 and SC-NEVPT3) up to the third order in the energy. At short internuclear distances the ⁷Δ_u state originates from the interaction of a ground-state ⁵D Fe atom with an excited-state ⁵F, whereas at large distances it results from the Van der Waals interaction of two ⁵D Fe atoms. At all levels of calculation the ⁹Σ^-_g term appears to have lower energy than the short-range ⁷Δ_u state and can thus be assigned as the ground state of the iron dimer. The spectroscopic constants of the ⁹Σ^-_g state (R_e=2.164 Å, ω_e=302.6 cm^-1 at the SC-NEVPT3 level of approximation) are in good accordance with the other high level ab initio calculations published thus far.

Mots clés: Physical Sciences

Domaines: Matière Condensée [cond-mat]

Renzo Cimiraglia, Celestino Angeli. A Multireference Perturbation Theory Study on the Fe₂ molecule: in quest of the ground state.. Molecular Physics, 2011, pp.1. ⟨10.1080/00268976.2011.566586⟩. ⟨hal-00687344⟩