Core overlap interactions in metals

Short-range interatomic forces associated with the overlap of closed core shells in both simple and noble metals have been investigated by means of the Heitler-London approach. The required overlap integrals were evaluated numerically; core orbitals were represented by neutral-atom Hartree-Fock wave functions. The calculated overlap interactions were found to vary exponentially with separation, as expected. For most simple metals, the overlap interaction is small compared with the screened-Coulomb interaction, until separations considerably smaller than the nearest-neighbor spacing are reached. In noble metals, on the other hand, the overlap and screened-Coulomb potentials are comparable at the nearest-neighbor position. Some general features of overlap potentials are discussed. The construction of a composite interatomic potential by interpolation between low- and high-energy theories is investigated