SEMIEMPIRICAL TIGHT-BINDING INTERATOMIC POTENTIALS BASED ON THE HUBBARD-MODEL

By use of the perturbation method for tie Hubbard model, we discuss th e contribution of the interatomic electron correlations to the cohesiv e energy in terms of the bond-order potential. With the first-order ap proximation for the bond order, we present a semiempirical tight-bindi ng model for the interatomic potential. Based on this model, the influ ence of the on-site Coulomb interaction on materials properties such a s phase stability, Cauchy pressure, and elastic anisotropy ratio is st udied. It is shown that although it is a pair-functional one, the pres ent model can describe very well the elastic properties and phase stab ilities of the bcc transition metals without resorting to angular bond ing or spline-function modeling. The model is also applied to calculat ing the epitaxial Bain paths. The results show that V, Nb, Cr, and W h ave a metastable tetragonal phase while Ta, Mo, and Fe do not. The vac ancy-formation energies and surface tensions calculated with the sugge sted parameters for V, Nb, Ta, and Fe are reasonable, while those for Cr, Mo, and W are not correct.