Localized and delocalized Is core-holes in DFT calculations

In DFT calculations of core-electron binding energies (CEBEs), one can use either localized or delocalized core-holes. In this Communication, we compare those two approaches applied to 20 molecules. The results indicate that the functional PW86-PW91, which gives excellent CEBEs for localized core holes, fails badly in treating delocalized core holes. The failure is probably quite general for all GGA functionals. The conclusion is obvious: one must use the localized core-holes when one uses Delta E(PW86-PW91) prediction for K-shell CEBEs. (c) 2007 Elsevier B.V. All rights reserved.