Physical genetics: Cross-breeding density functional theory and X-ray photoelectron spectroscopy to rationalize chemical shifts of binding energies in solid compounds

Like other spectroscopic methods XPS and AES show characteristic chemical shifts depending on the elemental matrix of a compound, however, a satisfactory rationalization of the variance of such values is often difficult. By an extension of a previous approach we present a theory in a unifying equation which combines several parameters - some of them resulting from DFT calculations - which influence the energy of the outgoing electrons and thereby seemingly the binding energy. By calculating Bader charges, atomic volumes and site potentials we have produced a data basis for a set of chalcogenides and halides of Ba, Zn, Pb and Cu to rationalize the spread of measured binding energies and Auger energies. It has thereby become possible to quantify different factors separately which bias the measurement of the kinetic energies of the outgoing core electrons, both the photo-emitted and the Auger electrons. Such an analysis can also trace special features of an open-shell configuration and even show up effects of a semiconductor-type.