Table 1 The lattice constants and cohesive energies of graphite and diamond computed by different exchange correlation functionals, including the Perdew-Becke-Ernzerhof functional for solids and surfaces (DFT/PBEsol), density functional constructed with a long-range dispersion correction (DFT-D2) and the van der Waals density functional (vdW-DF), compared with the relevant experimental data³¹. (The c/a ratio of graphite is set to 2.76 in present calculations)

From: The R3-carbon allotrope: a pathway towards glassy carbon under high pressure