Density functional investigation of Fen clusters (n ≤ 6) with Cr substitutions: UB3LYP/LanL2DZ calculation

Geometric parameters, binding energies, natural populations, natural electron configurations and magnetic moments are obtained for the clusters of Fen, Crn and Fen−xCrx (n = 2–6, x = 1–6) optimized under the constraint of well-defined point group symmetries at the UB3LYP/LanL2DZ level. The substitutional effects of Cr in Fen are found in optimized structure, binding energies and electronic structures. The binding energies of Fen are generally decreased by successive substitutions of Cr atoms for Fe atoms in the clusters. In the mixed Fe–Cr clusters most of Cr–Cr bond lengths are larger than the Fe–Fe and Fe–Cr bond lengths because of the strong repulsion due to the magnetic frustration between atoms. Among the Fe–Fe, Fe–Cr and Cr–Cr bond lengths in the mixed clusters, the trend is found to become larger in that order. The larger distances between atoms in the mixed clusters are mostly caused by the strong magnetic repulsion. The changes are associated with those of electronic structure caused by the Cr substitutions, especially with the extent of contribution of 4s and 3d electrons to bond.