First-principles calculation of cluster geometries and magnetization of pure Ni and Fe-Ni clusters

摘要

We report the results of ab initio calculations for Ni-N clusters with N varying in the range 2 <= N <= 16 as well as for Fe8Ni5 clusters using density functional theory within the generalized gradient approximation. The cluster geometries are relaxed with no symmetric constraints allowing for non-collinear magnetization density. The lowest-energy structures obtained are used to evaluate the magnetic moment, binding energy and the HOMO-LUMO gap of Ni-N clusters. The results are compared with experimental data and previous ab initio calculations. The properties of mixed 13-atom icosahedral clusters for a Fe8Ni5 composition are also investigated. The lowest-energy structure is determined by the Ni atoms occupying the surface positions and forming a ring with a large number of Fe-Ni bonds.