Configuration of transition-metal atoms on iridium-doped graphene

Our theoretical calculation and analysis show that the configuration of transition-metal (TM) atoms on iridium-doped graphene depends on the number of the d-state valence electrons of the TM atoms. TM atoms with three or less d-state valence electrons prefer to form a horizontal configuration and destroy the original C_3v symmetry of the substrate. If there are more than three (but not five) d-state valence electrons in a TM atom, the TM atom selects the site just on the top of the iridium atoms and thus forms a vertical configuration, and the C_3v symmetry of the iridium-doped graphene remains. For TM atoms with five d-state valence electrons and a closed s shell, the TM atoms and the iridium-doped graphene prefer to form an inclined configuration. The configuration regularity of the iridium-doped graphene-adsorbing TM atoms is attributed to the unique spin and orbital angular momentum of the electron in the iridium-doped graphene and the unique selection rule of the charge transfer under spin polarization. (paper)