Liquid Water Under Strong Electric Fields: Understanding the Phenomenon of Electrofreezing

Motivated by the crucial role that strong electric fields play in many aqueous systems, we have carried out molecular dynamics simulations, to probe, how the structure and properties of water change when it is subjected to strong external fields. In agreement with previous studies, we have found, that when a conventional classical force field is used, at field strengths above ~0.1 V/nm, the water dipoles are increasingly forced to align with the field, giving rise to a somewhat more viscous phase akin to a nematic liquid crystal. It has also been shown, that under even stronger fields, water will eventually freeze, however in contrast to previous studies, we have found, that in simulations at constant pressure, with sufficiently long trajectories, TIP4P-2005 water already electrofreezes at RT and 1 atm at a field strength of 2.2 V/nm. Crucially, this is lower, than the field strength at which significant auto-ionization is predicted to occur in liquid H₂O. The structural changes that facilitate crystallization will be discussed, the possibility of probing the competition between electrofreezing and ion conduction experimentally, or using reactive (classical or ab-initio) simulations will be examined, and preliminary results from reactive simulations will be presented.