▎ 摘　　要

We have systematically investigated the effects of lithium (Li) on AA and AB stacking sequences of bilayer graphene using density functional theory (DFT). To accurately describe the bonding that occurs in bilayer graphene, the following van der Waals corrected exchange correlation functionals were used, namely, vdW-DF revPBE, vdW-DF C09(x) and vdW-DF2 C09(x). Several configurations that contain two Li atoms were considered to examine the effects of the Li Li interaction on bilayer graphene. For all configurations considered, we observe a variation in formation energies predicted by these functionals. The vdW-DF revPBE consistently predicts the highest formation energies, and vdW-DF2 C09(x) gives the lowest. One of the Li-configurations (c(10(AB))) undergoes a spontaneous translation from the AB to AA stacking, and is found to be the most energetically stable configuration compared to the other configurations. It is found that the change in the interlayer distance caused by Li intercalation greatly depends on the exchange correlation functional used. The GGA-PBE shows a reduction in the interlayer distance while the van der Waals corrected exchange correlation functionals show an expansion. In the case of Li intercalated configurations, GGA gives nearly the same interlayer distances as vdW-DF revPBE, unlike in the pristine structures. The agreement of these two functionals is explicitly discussed. Even if the construction of these van der Waals corrected exchange correlation functionals was basically on the energetics (stability) and structural properties, our calculated workfunction for pristine bilayer graphene obtained using i.e., vdW-DF2 C09(x) agrees very well with the experimental data compared to GGA-PBE.