The reason for this discrepancy in intensity remains unclear and requires further investigation. For the free N-H and O-H stretches appearing above 3300 cm -1 , we again find that both CNEO-DFT methods (no-epc and epc17-2) yield the most accurate results. In contrast, the performance of DFT and CNEO-DFT with the epc17-1 functional is similar, with both methods overestimating the vibrational frequencies. Therefore, the good performance of CNEO-DFT with no-epc or epc17-2 is consistent for both bonded X-H vibrations and free X-H vibrations.