SCF LCAO MO Study of Li2

Abstract

An LCAO molecular orbital calculation using the full six-electron Hamiltonian has been performed on Li2 at a nuclear separation equal to the experimental internuclear distance. The molecular wave function consisted of one antisymmetrized product made up of molecular orbitals formed as the best linear combinations of Slater 1s, 2s, and 2pσ atomic orbitals. The orbital exponents for these atomic orbitals were respectively 2.69, 0.64, and 0.53 as determined by a variational calculation on the lithium atom. In computing the molecular dissociation energy, the energy of two separated lithium atoms was taken to be that obtained by this variational calculation. The computed dissociation energy was found to be 0.33 ev compared with the experimental value of 1.05 (where a slight correction for zero-point energy has been made). The ratio of the computed molecular ground-state energy to the experimental is 0.9902 while the difference of these quantities is 4.00 ev. Certain other molecular constants are calculated and compared with available experimental data.