Crystal structure prediction (CSP) aims to predict all possible polymorphs for a compound given only its molecular structure. This is usually approached through a computational exploration of the lattice energy surface to identify all low energy local minima, which correspond to putative stable crystal packings of the molecule being studied. The structures associated with each local energy minimum are ranked according to their predicted energy, with the assumption that the most likely observable crystal structure corresponds to the lowest energy predicted structure -the global energy minimum. The two greatest challenges in CSP are the high dimensionality of the relevant energy surface, which creates a challenge in locating all possible crystal structures, and the small energies that typically separate competing predicted crystal structures, meaning that high quality models are required for evaluating the relative energies of predicted crystal structures.