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).
| Graphite | PBEsol | vdW-DF | DFT-D2 | Expt. |
|---|---|---|---|---|
| a (Å) | 2.458 | 2.465 | 2.460 | 2.460 |
| EC(eV) | 8.29 | 7.99 | 8.41 | 7.37 |
| Diamond | PBEsol | vdW | DFT-D2 | Expt. |
| a (Å) | 3.554 | 3.574 | 3.545 | 3.54 |
| EC(eV) | 8.28 | 7.88 | 8.49 | 7.58 |