Hylleraas-type calculations of the relativistic corrections for the ground state of the lithium atom

Calculations of the principal Breit-Pauli relativistic corrections for the ground-state energy of the lithium atom have been carried out. The corrections have been determined using first-order perturbation theory. Only the non-fine-structure components of the Breit-Pauli Hamiltonian in the infinite nuclear mass approximation are considered. The wave function employed is an extensively optimized large-scale Hylleraas-type expansion. Comparisons are made with the few available relativistic corrections for the lithium atom that are available in the literature. A reevaluation of the first ionization potential for the ground state of Li is presented.