All higher level energy evaluations in this work are performed at the force field optimized structures, with no further optimization. For all three molecules, re-evaluation of the energies at the PBE and PBE0 levels of theory improve the position of the experimentally known crystal structures on their CSP landscapes (Figure ,c and SI). PBE retains the low energy of β -oxalic acid and brings the α polymorph to the global minimum, while PBE0 further increases the relative stability of α to around around 5 kJ mol -1 below that of β . These energy differences compare well with the lattice energy difference of around 3 kJ mol -1 between α and β when fully re-optimized at PBE0. Similarly, the known structure of urazole is re-ranked to the global energy minimum with PBE and 2nd lowest energy structure with PBE0, 1.04 kJ mol -1 above the global minimum. and the three polymorphs of maleic hydrazide are all brought closer to the global minimum with PBE and PBE0 (see Figs ). Thus, we conclude that single point energy re-evaluations using solid state DFT map the force field results for all three molecules to more realistic energy rankings in which the known experimental crystal forms are either the global minimum or very close to the global minimum on their respective landscapes. Empirically, we find that PBE provides slightly better rankings of the known crystal structures for all three molecules. However, for the purposes of developing the method, we treat PBE0 as the target for learning a high level energy. The performance of PBE0 might be limited by the single point nature of the energetic re-evaluation and, so, optimization on the GPR modelled energy surface is a clear next step of development, but is reserved for future work.