Extended Hartree—Fock Ground-State Wavefunctions for the Lithium Molecule

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Abstract
A configuration‐mixing method is described for single‐bonded diatomic molecules, in which both the orbitals from which the configurations are constructed, as well as the mixing coefficients, are optimized by way of solving SCF‐type equations. The method properly describes molecular formation, which is not in general possible when using the Hartree—Fock molecular‐orbital method. Numerical results are presented for the Li2 molecule. The calculated potential curve is closely parallel to an empirical curve obtained by using spectroscopic constants. The difference between the two curves may be interpreted as the correlation energy of the core electrons, and is essentially constant over the complete range of internuclear distances of chemical interest.