The FIT+DMA+MP2 model continues the trend towards improving results from the FIT+DMA model. The ∆E results highlight cases where the FIT+DMA+MP2 model out-performs the DFT-based models: for the three polymorphs of maleic hydrazide, urazole, and the α form of oxalic acid. ∆E using FIT+DMA+MP2 has increased relative to the FIT+DMA+B3LYP results for both forms of adenine, but the N lower results show that this is caused by a small number of predicted, but unobserved structures having low energies with FIT+DMA+MP2. The largest improvements that we observe between the wavefunction-based MP2 dimer-corrected model and the DFT-based models are in the ranking, N lower , for a few of the molecules. The most dramatic change is for the α polymorph of oxalic acid, which remained high on the energy landscape with all other models, but with FIT+DMA+MP2 is almost equi-energetic with β oxalic acid, as the two lowest energy crystal structures. The changes in the overall distribution of crystal structures and position of the known polymorphs with all four energy models is shown for oxalic acid in Fig. .