We also tested two simplified DFT schemes, HSE-3c and B97-3c, as possible intermediate energy models. Both methods use modified, smaller basis sets combined with semi-empirical corrections. B97-3c and HSE-3c lattice energies are both strongly correlated to the PW results (R 2 = 0.984 and 0.869, respectively, Fig. ). However, when the cost of calculations is taken into account, neither method offered an advantage over PBE/PW for the small molecules studied here.