Exchange energy functional from a Pauli correlationfactor model

The spherical average of the Hartree-Fock second-order density matrix is approximated through an ansatz similar to that proposed by McWeeny for the exact second-order density matrix. This leads to the definition of a Pauli correlation factor which produces the exchange hole. In this work, the Pauli correlation factor is modeled in order to obtain an exchange energy density functional. The factor satisfies the normalization condition of the second-order density matrix. Numerical results are presented for the atoms He-Ar. © 1993