Thus, it becomes more important to investigate the pseudo-translation and pseudo-rotational contributions. The angular deviations are considerable for all systems in different parts of the frequency spectrum. While there is no clear correlation between the angular deviations and the frequency errors, all normal modes with pronounced relative and absolute intensity errors have substantial angular deviations. Overall, the intensities obtained from the QM PHVA are largely reproduced by the QM/MM PHVA. Substantial errors were only observed for a few modes. Concerning frequencies, the errors are mostly below 10 cm -1 , but in some cases they are higher. Very high errors of 100 to 200 cm -1 are observed for normal modes involving hydrogen-bond donors, such as those in uracil in methanol and propanamide in water. For the formaldehyde in water system, expanding the QM subsystem to include the two hydrogen-bonded water molecules led to improvements in some vibrational modes but also had adverse effects on others. Notably, the C=O stretching mode was better reproduced, which is expected given the enhanced interaction with the solvent environment. The adverse effects could be due to an imbalanced description of the solvent environment. Thus, to gain an overall improved description, it would be preferable to enclose the solute with additional QM solvent molecules.