To date, theoretical studies of the CLS of defects in solids are relatively rare, not least because they are more computationally demanding. Modelling isolated point defects in bulk usually requires a large supercell to eliminate spurious interactions between periodic images. In addition, the CLS around defects often changes continuously, leading to tiny and insignificant fingerprints in the spectrum, which require sufficient sampling in the model. In addition, translating the CLS into experimentally observable spectral features, which is important for interpreting XPS results, is not as straightforward as in molecules.