Nuclear quantum effects and hydrogen bond fluctuations in water

There is no doubt about the importance of liquid water for climate and life on Earth. Correctly modeling the properties of this substance is still a formidable challenge, however. Here, we show, using state-of-the-art techniques that allow for quantum mechanical effects in the motion of the electrons and nuclei, that room-temperature water is not simply a molecular liquid; its protons experience wild excursions along the hydrogen bond (HB) network driven by quantum fluctuations, which result in an unexpectedly large probability of transient autoionization events. Moreover, these events are strongly correlated across neighboring bonds so that perturbations disrupting the HB network (pressure, confinement, solvated ions, and interfaces) could enhance in a concerted way their impact on water's behavior.