Scaling, Padé approximants and variation principles in the many-body perturbation theory of atomic and molecular properties

Scaling and Padé approximants in the many-body perturbation theory of atomic and molecular properties are discussed for both the double perturbation theory and the coupled Hartree-Fock perturbation expansion. A variational justification of the [2/1] Padé approximants to the correlation energy series is given. A numerical illustration of the use of the scaling technique in coupled Hartree-Fock, many-body perturbation theory calculations of dipole polarizabilities is presented.