Fig. 18. DDEC6 results for ice crystal using 12, 96, 324, 768, 1500, 2592, 4116, 6144, and 8748 atoms per unit cell (PBE/planewave method). These results show both the computational time and memory required scale linearly with increasing system size. Left: The computational time scales linearly with the number of atoms and decreases with increasing number of processors. Right: Total RAM required is almost independent of the number of processors. The predicted memory required is from eqn (17).