Up to this point we have discussed the behavior of an isolated molecule of ROY. Figure (b) reports the relative energies of the crystal polymorphs, computed using the monomer-correction scheme in Eq. ( ) using various levels of theory. As reported previously, the B86bPBE+XDM functional yields extremely poor relative energies with form Y, which is the thermodynamically most stable form, predicted to be the second-least stable polymorph. The relative order of the other lattice energies is also poor at this level of theory, relative to experimental lattice enthalpies or CCSD(T) lattice energies. Furthermore, replacing B86bPBE+XDM with another self-consistent GGA or hybrid functional does not meaningfully improve the energy rankings. In contrast, the DC-DFT models all perform much better. The close energy spacings of the ROY polymorphs make this a challenging problem for any method, but SCS-MP2D and DC-DFT with hybrid functionals all give fairly consistent qualitative rankings, even if the quantitative lattice energies differ.