Size dependence of structural stability and magnetization of nickel clusters from real-space pseudopotentials

Abstract

We examine the structural stability and magnetization for nickel clusters containing up to 500 atoms by performing first-principles calculations based on pseudopotential in real space computed within density-functional theory. After structural relaxation, Ni clusters in this size range favor either face-centered cubic (fcc) structure, which is a crystal structure in bulk, or icosahedral structure, which is expected for small clusters. The calculated total magnetic moments per atom of energetically stable clusters agree well with experiment, wherein the moments decrease non-monotonically toward the bulk value as cluster size increases. We analyze the spatial distribution of the local magnetic moment, which explains why the magnetic moments of Ni clusters are enhanced compared to their bulk value.