The diffusion coefficient of water (D water ) was experimentally observed to be 2.3 × 10 -9 m 2 s -1 , 33 while our simulations provided a value of 2.4 × 10 -9 m 2 s -1 (Table ). It has been experimentally observed that D water in a dilute aqueous TMAO solution (~0.2 mmol L -1 ) is ~10% lower than that in pure water. Thus, our nanosecond-order ab initio EFP-MD results successfully reproduced that TMAO slows the dynamics of water molecules.