A new extended Hartfree-Fock function: The omega function.I

Abstract

A new projection operator for building up wave-function for the ground state of atomic and molecular electronic systems is proposed. This operator interchanges essentially the α and β spin-functions of all the electron pairs in the wave-function. Using this new function, we call the omega function, the first order reduced density matrix and the natural configurational equivalence are deduced for the ground state of a four electron system. It is found that this function is roughly equivalent to a closed shell excited configuration expansion.