关键词: 铁原子, 氮分子, 密度泛函理论

Abstract: The side-on bounded FeN2 (s-FeN2 for short) structure was calculated using B3LYP/6-311+G(d) method. The geometric structures, electronic structures, energies, and vibrational frequencies were calculated for many stable electronic states, van der Waals force interaction states, and transition states with different spin multiplicities. The results showed that: (1) the Fe—N bond length R1 and N—N bond length R2 were close to each other among the same kind states; (2) the fourmost stable electronic states of the side-on bounded FeN2were 15B2, 15B1, 13B1, and 13B2, the energy differences were about 25 kJ·mol-1; the electronic structures of the triplet states were plentiful, most of the singlet states were much higher in total energies than triplets’ and quintets’; (3) there have no fragment orbital overlap and electron transfer in S-FeN2 when Fe atom takes on 3d64s2 configuration due to the strong electron repulsion between σ or π electron pairs. To the other excited-state configurations 4s13d7, 4s13d64p1, and 3d74p1, there were some electrons transfer from Fe atom to N2 molecule via σ(sd)-π and π-π* orbitals overlap, the systems present somewhat ionicity and the bond length of activated N2 is generally not larger than 120 pm, that means Fe atom cannot insert into N≡N; (4) if electrons were excited to the molecular orbitals composed by nitrogen molecule moiety π-orbitals, the N2 could be activated to single bond even dissociation.

Key words: Iron atom, Nitrogen molecule, Density functional theory