ATOMIC VALENCE CORRELATION ENERGIES FROM ABINITIO MODEL POTENTIAL CALCULATIONS

Ab initio model potential calculations on X-, X, and X+ (X = F, Cl, Br, and I) using CISD wavefunctions have been performed in order to test a recent conclusion on the irrelevance of the valence orbital internal nodes in the values of atomic valence correlation energies. The results show that the ab initio model potential orbitals, showing the correct nodal structure, provide valence correlation energies much closer to the corresponding all-electron values than nodeless pseudo-orbitals do.