DFT-D3 Study of Some Molecular Crystals

We investigate the performance of the dispersion correction D3 with and without an explicit three-body dispersion term for the energetic and structural properties of rare gas and molecular crystals. Therefore, the two- and three-body gradient of the dispersion energy is implemented in the periodic plane-wave program VASP. It is combined with different density functionals at the level of the general gradient approximation (GGA) and hybrid functionals. Cohesive energies and lattice parameters for the rare gas crystals Ar, Kr, and Xe and a set of 23 molecular crystals are calculated and compared to experimental reference values. In general, all tested methods yield very good results. For the molecular crystals the mean absolute deviation of lattice energies from reference data (about 1-2 kcal/mol) is close to or below their uncertainties. The influence of the three-body Axilrod-Teller-Muto dispersion term on energy and structure is found to be rather small. While on a GGA level cohesive energies become slightly worse, for hybrid functionals the three-body term improves the results.