Ab initio calculations with van der waals corrections: Benzene-benzene intermolecular case and graphite

For the benzene-benzene intermolecular case and graphite, we have performed ab initio density functional theory (DFT) calculations with van der Waals corrections. We use two DFT methods: the Vienna ab initio simulation package (VASP) and the Fritz Haber Institute ab initio molecular simulations package (FHI-aims). For the van der Waals description, we adopt Grimme's DFT-D2 approach in VASP while the Tkatchenko-Scheffler (TS) scheme is used in FHI-aims. First, we calculate the equilibrium distance between the in-plane benzene-dimer molecules by using the two methods. The equilibrium intermolecular distance obtained using the DFT-D2 scheme of Grimme is shorter than that obtained using the TS scheme. The equilibrium structural parameters of graphite are calculated by varying the lattice parameters a and c simultaneously and are compared with previous results.