Enhancement of the local asymmetry in the hydrogen bond network of liquid water by an ultrafast electric field pulse

Condensed phase electron decomposition analysis based on density functional theory has recently revealed an asymmetry in the hydrogen-bond network in liquid water, in the sense that a significant population of water molecules are simultaneously donating and accepting one strong hydrogen-bond and another substantially weaker one. Here we investigate this asymmetry, as well as broader structural and energetic features of water’s hydrogen-bond network, following the application of an intense electric field square pulse that invokes the ultrafast reorientation of water molecules. We find that the necessary field-strength required to invoke an ultrafast alignment in a picosecond time window is on the order of 10 8 Vm −1 . The resulting orientational anisotropy imposes an experimentally measurable signature on the structure and dynamics of the hydrogen-bond network, including its asymmetry, which is strongly enhanced. The dependence of the molecular reorientation dynamics on the field-strength can be understood by relating the magnitude of the water dipole–field interaction to the rotational kinetic energy, as well as the hydrogen-bond energy.