Water dynamics visited. A comprehensive DFT study of proton transfer in liquid water underscores the pivotal role of ion pairing phenomena

The core issue standing behind water's unique and extraordinary properties is proton transfer. The extremely fast nature (under the picosecond time scale) of proton transfers taking place in water convinced us to resort to a classic approach: a comprehensive DFT study of neutral, medium-sized water clusters (H ₂ O) _n (n up to 30). Our main objective was to determine the instantaneous (I) structures of the transition states of proton transfers, which are inaccessible by experimental techniques or molecular dynamics simulations. Subsequent IRC analysis and AIM treatment of the three stationary points thereby available for each transition state structure were fundamental to describing the basics of water dynamics. Actually, our study shows that proton transfers occurring in neutral, liquid water involve a variety of ion-pairing phenomena that operate not only on neutral waters clusters but also on neutral ion-pair clusters. The unveiled properties of water ion-pairs suggest that the long-standing assumption that water's ionic components do not interact with one another -a hypothesis that has remained unchallenged for over a century- may be erroneous. Water ion-pairs are at the center of the new paradigm, shedding light on water electrodynamics and offering plausible suggestions on the abiotic origin of life that are worth exploring.