The resonance Raman spectrum can be compared to the computed spectral density. In Figure , the simulated spectral densities for CV + in methanol are compared to the experimental resonance Raman spectrum that is given from 300-900 cm -1 in Ref 88. We see that the main peak in this spectral window at 600 cm -1 corresponding to the motion of the center oxazine ring is accurately captured by QM/MM, QUBEKit, and revQUBEKit MD. Smaller peaks at ∼530 cm -1 and ∼850 cm -1 , corresponding to a combination of NH 2 and C-H twisting motion and C-H in phase wagging motion, respectively, are well-captured by QM/MM AIMD, but less accurately simulated by QUBEKit and revQUBEKit FFMD. In sum, we observe that the QM/MM AIMD yields fairly good agreement with the vibrational frequencies measured for CV + in methanol, with QUBEKit and revQUBEKit FFMD also providing satisfactory results. This good agreement testifies to the high quality of our computed spectral densities, at least in the frequency window of 300-900 cm -1 .