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Fundamental Properties of Metal-Adsorbed Silicene: A DFT Study

Sodium, magnesium and aluminum adatoms, which, respectively, possess one, two and three valence electrons in terms of 3s, $3s^2$, and ($3s^2$, 3p) orbitals, are very suitable for helping us understand the adsorption-induced diverse phenomena. In this study, the revealing properties of metal (Na/Mg/Al)-adsorbed graphene systems are investigated by mean of the first-principles method. The single- and double-side chemisorption cases, the various adatom concentrations, the hollow/top/valley/bridge sites, and the buckled structures are taken into account. The hollow and valley adsorptions, which, respectively, correspond to the Na/Mg and Al cases, create the extremely non-uniform environments within the Moire superlattices. This lead to diverse orbital hybridizations in Na/Mg/Al-Si bonds, as indicated from the Na/Mg/Al-dominated bands, the spatial charge density distributions and the orbital-projected density of states (DOS). Among three kinds of metal-adatom adsorptions, the Al-adsorption configurations present the strongest chemical modifications. The ferromagnetic configurations are shown to only survive in the specific Mg- and Al-adsorptions, but not the Na-cases. The theoretical predictions could be validated by experimental measurements and the up-to-date potential applications are included. Furthermore, the important similarities and differences with the graphene-related systems are also discussed.