Nonvariational configuration interaction calculations by local scaling method

Abstract

To first order, the Hartree–Fock one-electron density of a given state of an N-electron system is identical to the exact density. For this reason, an accurate wave function must fulfill the necessary condition of yielding a one-electron density similar to the Hartree–Fock density. For a given configuration interaction (CI) wave function with arbitrary parameters, we have used the local scaling method in order to construct a modified CI wave function which associates a one-electron density exactly the same as the Hartree–Fock density. The resultant nonvariational CI wave function is shown to have an energy comparable to that from the variational CI calculation for the ground state of the helium atom.