Ab initio studies of small AlmFen clusters

The equilibrium geometrical structures of small Al_mFe_n clusters have been determined through ab initio calculation of the cluster total energy at the UB3LYP/Lanl2dz level. For dimers of iron and aluminum, the dissociation energies, the equilibrium atomic distances, and the vibrational frequencies were calculated. The agreement between calculations and experiments is reasonable. The ground stable geometrical structures of Fe₄, FeAl₃, Fe₃Al and Fe₂Al₂ clusters favor three-dimension configurations, but Al₄ tetramers are planar structures. The Al-rich tetramers are more stable than the other two composition tetramers. This is different from that of bulk alloys.