Application of the many-body Green's function formalism to the lithium atom

Abstract

The techniques of many‐body Green's function theory have been applied to the calculation of properties of the lithium atom. Using basis set expansion techniques and a second‐order expansion of the self‐energy, Dyson's equation was solved, and the first‐order reduced density matrix and the first ionization potential for the lithium ground state were computed. The natural spin orbitals of s symmetry were in excellent argeement with those computed from wavefunctions. The ionization potential was within 0.01 eV of the exact experimental result.