One example often explored via periodic DFT modeling in the context of FOs is graphene due to its unique 2D structure. It can serve as a model system to study impurities on surfaces. Parq et.al 155 investigated how ionized metal adsorbates on graphene can function as point-charge impurities to examine the charge response of graphene with its Dirac cone band structure (Fig. ). The authors focus on the physics behind the metal-atom-induced charge and spin polarization in graphene by modeling the scanning tunneling spectroscopy (STS) simulations based on DFT calculations. Their findings indicate that a Cs atom on graphene is fully ionized, displaying a significant band-bending feature in the STS, whereas the charge and magnetic states of Ba and La atoms on graphene are more complex due to orbital hybridization and Coulomb interaction.