Certain known polymorphs presented in Figure (d), such as structure I (mp-1102591), II (mp-1079207), and III (mp-655656) are positioned in regions not covered by the sampled structures. These were absent from the training set due to their high energy above the convex hull; a filter of 0.25 eV/atom was used to favour the generation of energetically favourable configurations. Indeed, most of the structures generated by Chemeleon exhibit energies below 0.15 eV/atom above the convex hull, according to MACE-MP as shown in Supplementary Figure . The entry mp-1102591 consists of densely packed TiO₂ octahedra in a cubic symmetry, while mp-1079207 features 7-fold coordinated Ti with hexagonal symmetry. Lastly, mp-655656 features a square pyramidal coordination of Ti, typically seen in TiO. However, the layers in this structure are spaced far apart, making it difficult for the generative model to sample.