Influence of external static and alternating electric fields on self-diffusion of water from molecular dynamics

Non-equilibrium molecular-dynamics simulations of liquid water have been performed in the canonical ensemble in the presence of both external static and oscillating electric fields of (r.m.s.) intensities 0.05 V/Å and 0.10 V/Å, with oscillating-field frequencies 50, 100 and 200 GHz. The rigid potential model TIP4P/2005 was used, and NEMD simulations were performed, including in the supercooled region, at temperatures ranging from 200 to 310 K. Significant alterations in the percentage dipole alignment and self-diffusion constant were found vis-à-vis zero-field conditions, as well as shifting of the probability distribution of individual molecular self-diffusivities. For instance, the application of static fields was typically found to reduce the self-diffusion of liquid water, effectively due to some extent of ‘dipole-locking’, or suppression of rotational motion, whilst diffusivity was found to be enhanced in oscillating fields, especially at high frequencies and outside the supercooled region.