ON INTRAPAIR AND INTERPAIR ELECTRON CORRELATIONS IN NAF2

This article presents the intrapair and interpair electron correlation energies of the NaF2. The total interpair correlation energy predomin ates. Thus, the interpair correlation energy is very important in buil ding models for correcting post Hartree-Fock calculations in order to obtain accurate electron correlation energies. Based on this result an d our previous results, the elementary assumption underlying the so-ca lled ''higher lever correction'' in the Pople G1 and G2 theories is fl awed. (C) 1997 Elsevier Science B.V.