  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.
