As the embeddings are learned such that species which occur within similar environments should be similar, ionic representations may provide the flexibility to describe different types of compounds containing the same element. For example, TiO 2 containing Ti 4+ has a wide band gap above 3 eV, while Ti 2 O 3 containing Ti 3+ has a small band gap closer to 0 eV. This flexibility may not be captured by atom-only representations.