Tackling the Peak Assignment Problem in X-ray Photoelectron Spectroscopy with First Principles Calculations

ongoing

X-ray Photoelectron Spectroscopy (XPS) is one of the most widely used methods of characterization in applied surface science. It is applied in studies of heterogeneous catalysis, environmental degradation, corrosion, the manufacture of surface coatings, and various other processes. However, the practical value of XPS measurements is currently negatively affected by widespread problems in the analysis of recorded spectra. These have been extensively discussed in recent scientific literature, and problems with peak fitting and peak assignment in core level XPS have been identified as a source of significant errors in the analysis of XPS spectra. These problems can limit the amount of useful chemical insights that XPS is able to provide, and moreover, incorrect peak assignments can lead to the wrong conclusions being drawn about the underlying chemistry. The aim of this research project is to tackle these problems by enabling and encouraging the more widespread use of computational methods in the interpretation of experimental XPS spectra, and to thereby make XPS a more reliable and more useful method of characterization. Specifically, we want to make existing computational methods for calculating core electron binding energies and simulating core level spectra accessible to a wider community of researchers, and to improve these methods such that they would better meet the needs of XPS users. We will develop new, computationally efficient and user-friendly implementations of the ΔSCF method and the GW+cumulant approach, carry out case-studies that are designed to test the limits of current theories in guiding the analysis of real world spectra, and organize workshops and write tutorials to increase the user base of the computational techniques. The planned work will be carried out by an international, interdisciplinary and intersectoral team of experts in theoretical spectroscopy, developers of electronic structure codes, XPS users, and instrument manufacturers.