spd tight-binding model of magnetism in transition metals:: Application to Rh and Pd clusters and slabs

An efficient spd tight-binding model is extended to the case of spin-polarized materials by including electron-electron interactions in a multiband Hubbard model treated in the Hartree-Fock approximation. The tight-binding parameters are determined from a fit to bulk ab initio calculations, whereas the Coulomb and exchange integrals are derived from calculations on free atoms and reduced by constant factors to take metallic screening into account. We apply our method to rhodium and palladium clusters and slabs. The results are compared with first-principle calculations and experiments. The agreement is excellent and thus this method should be very useful to study complex structures, extended defects, and large clusters. This possibility is illustrated on large Rh and Pd clusters containing up to 201 atoms.