Frontier orbitals analysis and density-functional energetics for metal-substituted fullerene C58Fe2

Abstract

The formation mechanism, geometric structures, and electronic properties of a metal-substituted fullerene C58Fe2 have been studied using frontier orbital theory (FOT) and density functional theory (DFT). FOT predicts that two Fe atoms prefer to substitute the two carbons of a [6,6] double bond of C60 yielding a structure denoted as C58Fe2-3, which is different from the two equivalent substitution sites, i.e., the sites on the opposite of C60 cage or in the nearest neighboring sites of a pentagonal ring for C58X2 (X=N and B), and also different from the cross sites of a hexagonal ring for C58Si2. Five possible structures of C58Fe2 are optimized using DFT to see whether FOT works. The DFT calculations support the prediction of FOT. The Mulliken charge of Fe atom in C58Fe2-3 shows that the two Fe atoms of C58Fe2-3 lose 0.70 electron to the carbons of the cage, and the net spin populations of Fe atom indicate that each Fe atom has 1.11 μB magnetic moments, while each of the four nearest neighboring carbons has $-0.064~\mu_B$ magnetic moments. Thus, the two Fe atoms have ferromagnetic interaction with each other, and have weak antiferromagnetic interaction with their four nearest neighboring carbons, leaving 2.0 μB magnetic moments for the molecule.