Distinguishable Electron Method (DEM) for Electronic Structure Calculations. II. Derivation of Accessible Correlation Expressions for Physical Properties and Application to the Polarizability of Two-Electron Atoms

Abstract

The distinguishable electron method is extended to the calculation of physical properties other than the energy. Such calculations utilize accessible correlation expressions containing no correlated wavefunctions. It is shown that the necessary perturbation functions can be obtained from solutions of one-electron differential equations. For purposes of illustration, our method is applied to the polarizability of the helium sequence, starting with an open-shell screened nucleus initial approximation. Three different sets of optimized screening constants are employed. The best set—obtained by a new procedure which depends upon the property—yields polarizabilities that agree well with experiment and are superior to the perturbed coupled Hartree–Fock method.