For the two known polymorphs of oxalic acid, for example, both FIT+DMA+PBE and FIT+DMA+B3LYP predict the β form as the global minimum, whereas the α form is much higher in the landscape, while FIT+DMA+MP2 predicts α and β as the two lowest energy structures (Fig. ). The differences between models can be further assessed by comparison to the polymorphic relative stabilities determined by experimental methods and solid state quantum mechanical calculations.