Relatively large deformation energies are also found for ATS and DON. In these cases, there is only one major contribution, either from framework deformation (DON) or from the deformation of CBZ (ATS). The inspection of the molecular structures of adsorbed CBZ molecules in the lowest-energy configurations reveals a relationship between ∆ , and the angle between the planes defined by the two phenyl rings (defined as shown in Figure ): This angle amounts to 48.3° in free CBZ, but is reduced to values of 42° or lower in all cases where , exceeds 5 kJ mol -1 , with the smallest values of about 28° being found for BEA and ATS, the two zeolites having the largest deformation energy (Table ).