Fig. 2. The NQF contribution to the total energy (per molecule) of a q-TIP4P/F water model37 containing 256 water molecules within a periodic box. The results are shown as a function of the number of beads at 300 K. The blue circles are the results of the conventional PIMD approach (PI) and the red triangles show the performance of the developed method (PPI). For both PI and PPI calculations we use the same MD trajectories.