First-principles study of absolute XPS binding energy with PAW planewave pseudopotential method: application to tungsten disulfides

We propose an efficient theoretical method to take into account the core-hole spin density in the projector augmented wave method, combined with spin un-polarized pseudopotentials and the planewave basis set. We apply this method to the calculation of absolute core level X-ray photoelectron spectroscopy binding energies of WS2 and its related materials, and find the following points. First, inclusion of core-hole spin in the core-exited state is essential for accurate description of the binding energies, especially for light elements. Second, the calculated absolute binding energies show excellent agreement with experimental results. Finally, when oxygen atoms are incorporated in the basal plane of WS2 in the metallic phase, the O 1s binding energy is expected to appear at lower energy than the corresponding value in the semiconducting phase.