For multiple harmonic oscillators, the assignment of mode energies E will lead to different variants of the direct NVE schemes. Specifically, the NVE -zpe method assigns the corresponding harmonic zero-point energy to each mode, and therefore, if the inter-mode energy transfer is neglected and there is no zero-point leakage issue, the intensity of each mode can be obtained by performing a Fourier transform on the dipole derivative autocorrelation function and then dividing a prefactor based on the respective mode energy. The NVE -nms method conserves the total energy but assigns energies randomly to each mode using the normal mode sampling technique. With sufficient trajectory sampling, this method satis-fies the energy equipartition condition among each mode and therefore the intensities can be obtained directly by Fourier transforming the dipole derivative autocorrelation functions.