Tight-binding study of the ionization of iron clusters

A microscopic calculation of the ionization potential of ferromagnetic FeN clusters (3{≤}N{≤}89) has been performed. The spin-polarized electronic structure is calculated by self-consistently solving a tight-binding Hamiltonian for the 3d, 4s, and 4p valence electrons. Different isomers (open and compact, symmetric and asymmetric) are considered for N{≤}8. As a general trend, the extracted electron has the d character of minority spin orbitals mainly located in the outer atomic shells. Good agreement with experiment has been obtained for N{≤}7 using structures taken from ab initio molecular dynamics simulations and for N{≥}23 using bcc-like structures. The effects of the geometry and of the relaxation of the interatomic distances have been studied for N8. The results for bcc structures in the intermediate-size range (8N23) are not satisfactory. {} 1996 The American Physical Society.