The 9Sigma_g^- and 7Δu 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 7Δu 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 atoms. At all levels of calculation the 9Sigma_g^- term appears to have lower energy than the short-range 7Δu state and can thus be assigned as the ground state of the iron dimer. The spectroscopic constants of the 9Sigma_g^- state (Re = 2.164 A, ωe = 302.6 cm-1 at the SC-NEVPT3 level of approximation) are in good accordance with the other high level ab initio calculation published thus far.
A multireference perturbation theory study on the Fe2 molecule: in quest of the ground state
ANGELI, Celestino;CIMIRAGLIA, Renzo
2011
Abstract
The 9Sigma_g^- and 7Δu 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 7Δu 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 atoms. At all levels of calculation the 9Sigma_g^- term appears to have lower energy than the short-range 7Δu state and can thus be assigned as the ground state of the iron dimer. The spectroscopic constants of the 9Sigma_g^- state (Re = 2.164 A, ωe = 302.6 cm-1 at the SC-NEVPT3 level of approximation) are in good accordance with the other high level ab initio calculation published thus far.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
