A 20 ps NVT simulation was first performed, and then uncorrelated configurations from the later 15 ps were picked as initial configurations for subsequent 2 ps NVE simulations. As power spectra reflect the energy distribution among different vibrational modes, we can see from Figure (a) that energy is about equally distributed among different modes from the direct NVE scheme, which leads to good agreement between its IR spectrum and the experimental spectrum. For the direct NVT scheme, from the power spectrum, we can see that with the same amount of total simulation time as the NVE -eqp method, energy equipartition in the direct NVT scheme is far from being achieved. Specifically for this trajectory, energies of the O-H and C-H stretch modes above 2500 cm -1 are much lower than the remaining modes, which leads to weak IR intensities for the highly IR active C-H and O-H stretch modes in the experimental spectrum. This observation agrees well with previous literature that similar unequal energy distributions across different vibrational modes were observed for a single methanol molecule in conventional AIMD simulations. As to the NVT-NVE scheme, here the spectra were obtained from an average of 30 2 ps NVE trajectories, whose initial configurations were sampled every 500 fs from an NVT trajectory. This choice of 500 fs sampling time gap is justified by the fast decay of autocorrelation functions of the NVT trajectory (Figure ). From the power and IR spectra, it can be seen that the results from the NVT-NVE scheme are close to the direct NVE schemes and in good agreement with the experimental spectrum as well.