Fig. 5. (a) Total potential energy of Mg inserted into 2-layer phosphorene with respect to phosphorene–phosphorene distance (insert I, Mg inserted with the original channel size of 3.07 Å; insert II, Mg inserted with the most stable channel size of 4.84 Å); (b) binding energies with respect to the Mg concentration; (c) the most stable binding site of Mg inserting onto the 2-layer black phosphorus; (d) charge density difference between Mg and 2-layer black phosphorus.