Structural and magnetic properties of Fe-Ni clusters

摘要

Structural and magnetic properties of single-elemental and mixed 5-atom and 13-atom icosahedral-like Fe-Ni clusters of different compositions have been calculated in the framework of density functional theory in the generalized gradient approximation. We have allowed for a non-collinear magnetization density and full relaxation of the atoms without imposing any symmetry constraints. We find that the lowest-energy structures are given by distorted geometries with a maximum number of Fe-Fe bonds and a small number of Ni-Ni bonds, and the subsequent maximization of Fe-Fe and Fe-Ni bonds is suggested as a rule to predict the arrangement of the atoms in any lowest-energy isomer of an Fe-Ni cluster. Although for special geometries we obtain antiferromagnetic-like ground states with strongly reduced magnetic moments, the most stable clusters are characterized by collinear, ferromagnetic alignments of the spins.