Structural, bonding, and magnetic properties of Fen–xSix (n, x⩽6) clusters: Theoretical investigation based on density functional theory

The structural, bonding, and magnetic properties of clusters of Fen, Sin, and Fen–xSix (n = 2–6, x = 1–6) optimized at the B3LYP/LanL2DZ level with symmetry constraints are determined. The effects of the substitution of Si in Fen on the properties of Fen are identified and discussed. The cohesion of the Fe cluster is nonmonotonically increased by the successive Si substitutions. In the mixed Fe–Si clusters, the Fe–Fe bond lengths are not affected by the Si substitutions and are similar to those in Fe clusters as well as the Fe–Si bond lengths in mixed clusters. Most of the Si–Si bond lengths in mixed clusters are similar to those in Si clusters, while a few Si–Si bond lengths characterized by the hybridization with high s-character are smaller than or equal to that in Si2. Several distances between neighboring atoms at equator in the mixed clusters are found to be remarkably large, and there is the lack of bonding between them. The average magnetic moments of mixed clusters decrease nonmonotonically with the number of Si atoms, and approach those of Si clusters. There are large amount of spin on Fe atoms and small amount of spin on Si atoms in the mixed clusters. Most of the local atomic moments on Si atoms align antiferromagnetically with respect to those on Fe atoms. The properties of Fe clusters with Si substitutions result from the electron transfer from Fe to its surrounding Si atoms. The electron transfer is closely connected with the properties of Fe–Si alloys.