DFT calculations of energy dependent XPS valence band spectra

Highlights: • The valence band XPS spectra of SiO₂, PbO₂, CeVO₄, In₂O₃ and ZnO and the dependency on the excitation energy has been investigated with the new WIEN2k PES module. • In general good agreement between the simulated and experimental spectra has been achieved. • Unexpected features like significant Pb-6d contributions in PbO₂ or Zn-4p contributions in ZnO have been detected leading to better agreement with experiment than previous simulations. - Abstract: In the past few years it became regularly possible to measure valence band X-ray photoelectron spectra (XPS) using variable excitation energies. This ranges from UV-light to conventional X-ray sources (like Al K_α) all the way to synchrotron radiation with energies of several keV. In order to explain the observed variations in intensity with respect to the excitation energy, we performed XPS calculations using the WIEN2k code. The new PES module computes the XPS spectra using a combination of partial density of states times excitation-energy-dependent atomic-orbital cross sections. It considers as additional correction the charge fraction of the corresponding orbital located inside the atomic spheres. The resulting XPS spectra are compared with experimental data for SiO₂, PbO₂, CeVO₄, In₂O₃ and ZnO at different excitation energies and in general good agreement between the simulated and experimental spectra has been achieved. In some cases significant unexpected contributions like Pb-6d in PbO₂ or Zn-4p in ZnO appear and explain some features in the experimental spectra which previously have not been identified.