Structural, bonding, and magnetic properties of small Fen–xMox (n, x ≤ 6) clusters

The structural, bonding, and magnetic properties of clusters of Fen, Mon, and Fen–xMox (n = 2–6, x = 1–6) optimized at the B3LYP/LanL2DZ level with symmetry constraints are determined. The effects of the substitution of Mo in Fen on the properties of Fen are identified and discussed. While the cohesion of the Fe cluster is affected only to a small extent by the Mo substitutions, the structure of the cluster changes remarkably. In the mixed Fe–Mo clusters, the Mo–Mo bonds are shorter than the Fe–Fe and Fe–Mo bonds. The smaller distances between adjacent Mo atoms result from the strong d-contribution to bonding. On the other hand, the larger distances between Fe atoms mostly result from the strong magnetic repulsion associated with ferromagnetic coupling. The local moments of the Mo atoms are aligned in antiferromagnetic order. The variations in structural and magnetic properties of Fe clusters due to the Mo distributions are considered to be closely associated with the mechanical and magnetic hardening of Fe–Mo alloys.