The half-projected Hartree-Fock method

Abstract

A SCF method based on the solution of two eigenvalue problems, in the same manner as for the normal UHF procedure, is formulated for determining the half-projected Hartree-Fock (HPHF) function for singlet ground states of molecules, the HPHF function being defined as a linear combination of two Slater determinants containing only spin eigenfunctions with even quantum number. A computer program has been written and is described, and results are presented for two simple linear molecules. An important part of the correlation energy is obtained for these molecules.