Molecular dynamics simulation of the proton transport in water

Abstract

AbstractThe proton transport in water is treated within a mixed molecular dynamic (MD) and Monte Carlo (MC) scheme. Therein the migration of a positive charge is treated as a two step process; (i) as a displacement of a hydronium ion and (ii) as a proton transfer between a hydronium ion and an adjacent water molecule. Both, the hydronium ion and the water molecules are treated as rigid molecules. It is found that the determining step for the proton transport rate is the dissociation rate of H5O2+ complexes. In these complexes the O‐O distance is only 2.4–2.5 Å while the corresponding distance for two water molecules in solution is 2.83 Å. In the H5O2+ complex the proton does no longer belong to a single water molecule, but is delocalized between the two oxygen atoms. This situation is modelled by an exchange of the water and the hydronium every time step with a probability p = 1/2.