title: Special pair dance and partner selection: elementary steps in proton transport in liquid water.
abstract: Conditional and time-dependent radial distribution functions reveal the details of the water structure surrounding the hydronium during the proton mobility process. Using this methodology for classical multistate empirical valence bond (MS-EVB) and ab initio molecular dynamics trajectories, as well as quantal MS-EVB trajectories, we supply statistical proof that proton hops in liquid water occur by a transition from the H3O+[3H2O] Eigen-complex, via the H5O2+ Zundel-complex, to a H3O+[3H2O] centered on a neighboring water molecule. In the "resting period" before a transition, there is a distorted hydronium with one of its water ligands at a shorter distance and another at a longer distance than average. The identity of this "special partner" interchanges rapidly within the three first-shell water ligands. This is coupled to cleavage of an acceptor-type hydrogen bond. Just before the transition, a partner is selected by an additional translation of the H3O+ moiety in its direction, possibly enabled by loosening of donor-type hydrogen bonds on the opposite side. We monitor the transition in real time, showing how the average structure is converted to a distorted H5O2+ cation constituting the transitional complex for proton hopping between water molecules.
authors.affiliation: Institute of Chemistry and the Fritz Haber Research Center, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Omer
authors.initials: O
authors.lastname: Markovitch
authors.forename: Hanning
authors.initials: H
authors.lastname: Chen
authors.forename: Sergei
authors.initials: S
authors.lastname: Izvekov
authors.forename: Francesco
authors.initials: F
authors.lastname: Paesani
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Voth
authors.forename: Noam
authors.initials: N
authors.lastname: Agmon
mesh_terms: D005609:Free Radicals / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry; D011522:Protons; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D011522:Protons; D014867:Water; D010100:Oxygen