For our systems, it is to some degree due to the higher number of high-intensity normal modes in IR compared to Raman. Also, it is worth noting that the solvent environment contributes to some high-frequency modes that are usually considered to be very local, e.g., normal mode 1 of propanamide in water. Hence, one cannot assume that all high-frequency modes will not be affected by the PHVA approximation. The inclusion of water molecules in the partial Hessian of the formaldehyde in water system did not impact the local modes of the formaldehyde but resulted in high errors in the delocalized normal modes corresponding to intermolecular modes within the formaldehyde-water cluster and in the normal modes of the two included water molecules.