Ground-state potential curves forAl2andAl26+in the repulsive region

Abstract

Self-consistent-field (SCF) calculations have been performed for the short-range interaction between two aluminum atoms. The ground-state potential curve (${}_{}{}^3{}_{}{}^{}\Sigma _g^{-}{}_{}{}^{}\to {}_{}{}^5{}_{}{}^{}\Sigma _u^{-}{}_{}{}^{}\to {}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}\to {}_{}{}^1{}_{}{}^{}\Sigma _g^{+}{}_{}{}^{}\to {}_{}{}^3{}_{}{}^{}\Pi _g^{}{}_{}{}^{}$) is presented for internuclear separations between $R_e$ and 0.1 a.u. (repulsive energies up to ∼ ${10}^3$ a.u.). Basis sets consist of scaled eventempered Slater orbitals of double-$\zeta$ quality, augmented by diffuse functions, with the addition of united or semiunited atom-basis sets centered on the bond. The SCF potentials are compared with Thomas-Fermi theory and with the electron-gas calculations of Wilson, Haggmark, and Biersack. A kink in the SCF screening function is found near $R=2\mathrm{}$ a.u. This feature is believed related to changes in the ground-state configuration that occur in this region. Additional calculations (SCF and linear combination of atomic orbitals) were performed on ${\mathrm{Al}}_2^{6+}$ to determine individually the core overlap and the valence-electron contributions to the interatomic potential. The core-overlap interaction is compared with Gordon-Kim electron-gas calculations. Schematic calculations were also performed on the A1-${\mathrm{A}1\mathrm{}}^{3+}$ system to estimate the interaction between an atom and an energetic ion.