Modified bielectronic potential method for correlation energy

Lowdin's correlation potential formalism (1969) has been used to define a modified bielectronic potential, allowing one to calculate the exact electronic energy, given the Hartree-Fock wave function. This modified potential is in principle peculiar to each electronic system, and is defined by a correlation factor depending on the interelectronic distance /b r//sub 12/. The explicit calculation of the correlation factor has been performed for some two-electron atoms, in the 1/sup 1//b S/ and 2/sup 3//b S/ states, and for the beryllium atom. Examination of the results so obtained leads the author to conclude in favor of the nonexistence of a universal modified bielectronic potential.