Asymmetric self-diffusion with orientation-dependence of water molecule in finite timescale

Abstract

Self-diffusion of water has been investigated by molecular dynamics simulations. It was found that the preference of the direction in self-diffusion of water is orientation dependent in a finite time. For a time of ~100 ps, there are more possibilities for water molecules moving along the initial dipole orientation than in the opposite direction. This reveals that self-diffusion of water molecules is asymmetric in a finite time. We tested four water models and found that they all show similar asymmetric diffusion, indicating that asymmetric diffusion of water is intrinsic behavior rather than induced by the water model. These results are important for understanding and application of asymmetric diffusion in research fields such as biological water and confined water in small dimensions.