Finally, it is useful to revisit previous experimental findings in the context of the present work, and to discuss possible ways to verify the findings experimentally. With regard to GeO2 zeotypes, some previous studies have already shown a tendency of the d4r units to distort. This distortion is sometimes visible as a disorder of the edge oxygen atoms over different positions. On the other hand, the formation of short Al-F or Ga-F bonds has, so far, not been observed in AlPO4