An energy functional of electron-pair density

Abstract

The electron-pair (or intracule) density is the probability density function for an interelectronic vector and is intimately related to the electron correlation in many-electron systems. Based on the local scaling method, a theory is presented for the direct variational determination of the electron-pair density. Illustrative applications are given for the ground state of the helium atom. Simple electron-pair density functions are reported which compare quantitatively with the exact density.