Role of differential correlation energy in core ionization of pyrrole and pyridine

DeltaHartree-Fock (DeltaHF) and DeltaKohn-Sham (DeltaKS) orbital theories are used to calculate C(1s) and N(1s) core electron binding energies and chemical shifts of pyrrole and pyridine molecules. As a result, combination of DeltaKS and B3LYP functional appears as a very promising approach for the determination of the core excitation/ionization energies. For the carbon series in pyridine, electronic correlation is essential in correctly predicting the relative shifts among carbon atoms. A strong dynamical differential correlation energy for carbon and nitrogen has been revealed and can be related to the large magnitude of electronic transfer from ligands to the core ionized site. (C) 2004 Elsevier B.V. All Rights Reserved.