The AGP wavefunction and its relation to other descriptions of electronic structure

The recent proof that the consistent ground state of polarization propagator in the random phase approximation (RPA) necessarily has the form of an antisymmetrized geminal power (AGP) prompts the reinvestigation of this type of wavefunction. We emphasize the importance of model Hamiltonians and the parallellism between the treatments of the electron propagator and the polarization propagator. An energy optimized (AGP) ground state for LiH is presented in a limited orbital basis.