Furthermore, at short intermolecular distances, the overlap of wave functions opens the possibility of a charge migration between Py and the Au cluster. In those cases, the effect of intermolecular CT on the Raman signal should not be neglected, which may otherwise limit the applicability of the current QM/DIM scheme for Raman spectral simulations. It is therefore desirable to develop a scheme to account for the CT effect in future QM/MM methods. The use of only QM-QM block Hessian matrix in the current work is also a potential source of small errors in the simulated vibrational spectra. In addition, the vdW interaction between the molecule and MNP could affect the optimized molecular structure and then its vibrational frequencies predicted by using the QM/DIM method.