Structural dependence of electronic and magnetic properties of the Cr13 cluster

A tight-binding effective potential has been employed, in conjunction with a genetic algorithm, to fully optimize the Cr-13 cluster geometry without imposing any symmetry constraints. The minimum energy structure of this cluster is found to be a slightly distorted icosahedron. Based on the optimized structure and three assumed geometries (icosahedron, bcc-like and fcc-like), the structural dependence of electronic and magnetic properties of the Cr-13 cluster is discussed by using a d-band Hubbard-like Hamiltonian in the unrestricted Hartree-Fock approximation. Results are given for the average magnetic moment and local magnetic moments. It is found that for all considered geometries the Cr-13 cluster exhibits antiferromagnetic behavior. Results are also given for the cohesive energy, average coordination number, and local electronic densities of states. The results indicate that the average coordination number per atom in the cluster geometry is a significant factor to affect the magnetism. Also, the local density of states is a sensitive function of geometry.