Modulation of the work function of graphene by Na and Cl co-adsorbed on opposite sides on graphene

The influence of Na and Cl atoms adsorption on the work functions (WF) of graphene was investigated by first-principles calculations. The WF of graphene increase or decrease significantly by a single Na or Cl atom adsorption. When Na and Cl adatoms were co-adsorbed on opposite sides of grapheme, there is a little change in WF of grapheme, but there is great difference of the WF between the two sides.