A DFT-based procedure for predicting core-electron binding energies of chemisorbed molecules using small cluster models: first tests on CO on Ni(100), Pd(100) and Pd(110)

A new method is proposed for the accurate prediction of core-electron binding energies of molecules chemisorbed on metallic clusters as models for metallic surfaces. It involves a formal two-step path in which only the excitation energy from the desired core-level to the conduction band of the cluster is calculated via DFT, the remainder being replaced by the experimental work function of the crystallographic face. Using CO adsorbed on small (n = 1–4) Nin and Pdn clusters as examples, the computed C1s and O1s energies show an average absolute deviation of only 0.55 eV, i.e. about three times lower that with direct ΔSCF calculations which actually involve a core-ionized species.