Reduced Green’s functions and coupled perturbed Hartree–Fock calculations. II. Application to the static dipole polarizability of the helium isoelectronic sequence

Abstract

The reduced free-particle Green’s function formulation of the first-order coupled perturbed Hartree–Fock theory is applied to the calculation of the static dipole polarizability for the helium atom and for two-electron ions as a test of the formulation and to demonstrate a power-moment method of solution. The power-moment method reduces the first-order coupled perturbed Hartree–Fock (FO-CPHF) integral equation to a set of simultaneous linear equations tailored to fit the problem. The formalism facilitates a consistent treatment of three approximations to the coupled perturbed method, depending upon the potential from which the unoccupied states (appearing in the corrected Green’s function) are derived. In each case the occupied (hole) states are accurate series solutions to the zero-order Hartree–Fock equations. Results in agreement with previous calculations are reported for the helium isoelectronic sequence.