First-principles multiscale modelling of charged adsorbates on doped graphene

Adsorbed atoms and molecules play an important role in controlling and tuning the functional properties of two-dimensional (2D) materials. Understanding and predicting this process from theory is challenging because of the need to capture the complex interplay between the local chemistry and the long-range screening response. To address this problem, we present a first-principles multiscale approach that combines linear-scaling density-functional theory, continuum screening theory and large-scale tight-binding simulations into a seamless parameter-free theory of adsorbates on 2D materials. We apply this method to investigate the electronic structure of doped graphene with a single calcium (Ca) adatom and find that the Ca atom acts as a Coulomb impurity which modifies the graphene local density of states (LDOS) within a distance of several nanometres in its vicinity. We also observe an important doping dependence of the graphene LDOS near the Ca atom, which gives insights into electronic screening in graphene. Our multiscale framework opens up the possibility of investigating complex mesoscale adsorbate configurations on 2D materials relevant to real devices.