However, the challenge is that in simulations on systems with relatively weak mode couplings, the energy flow is slow, and it could take a long time to reach ergodicity and energy equipartition. Here we propose a slightly different NVE variant in which we start the NVE simulations from configurations with energy equipartition preset (NVE -eqp), i.e., all modes begin with the same mode energy. Admittedly, this initial condition is less physical than the initial condition obtained from normal mode sampling and will artificially favor those configurations close to energy equipartition during the dynamics simulations, but we will show later that it presents higher computational efficiency, and the simulated spectra are reasonably accurate compared to experimental results in a series of highly challenging water cluster systems.