Element-specific relativistic corrections from Ref. 102 were added to the absolute CEBEs: 0.14 eV for carbon, 0.28 eV for nitrogen, 0.51 eV for oxygen, and 0.85 eV for fluorine. (Similar values have been used in other recent studies of K-shell ionization. ) For molecules that have symmetry-equivalent atoms, the Boys localization procedure 104 is used prior to the ∆SCF and fractionaloccupancy calculations.