where E int is the interaction energy, E slab-P D-N 2 is the DFT energy of the model system in Fig. , E slab is the energy of the lithium slab alone, and E P D and E N 2 are the energies of the PD and the nitrogen molecule respectively. In a system without the PD, E int is the interaction energy of lithium and nitrogen and collapses to the adsorption energy. It is worth noting that the interaction energy of the surface captures the interactions between all three molecules (Fig. ). To isolate the energy of the lithium-nitrogen interaction (E(Li -N 2 )), the PD is removed from the surface after the final configuration is obtained and the total energy is calculated for this fixed system.