Semiempirical tight-binding interatomic potentials based on the Hubbard model

Abstract

By use of the perturbation method for the Hubbard model, we discuss the contribution of the interatomic electron correlations to the cohesive energy in terms of the bond-order potential. With the first-order approximation for the bond order, we present a semiempirical tight-binding model for the interatomic potential. Based on this model, the influence of the on-site Coulomb interaction on materials properties such as phase stability, Cauchy pressure, and elastic anisotropy ratio is studied. It is shown that although it is a pair-functional one, the present model can describe very well the elastic properties and phase stabilities of the bcc transition metals without resorting to angular bonding or spline-function modeling. The model is also applied to calculating the epitaxial Bain paths. The results show that V, Nb, Cr, and W have a metastable tetragonal phase while Ta, Mo, and Fe do not. The vacancy-formation energies and surface tensions calculated with the suggested parameters for V, Nb, Ta, and Fe are reasonable, while those for Cr, Mo, and W are not correct.