An improved understanding of proton-transport mechanisms in aqueous and hydrophilic systems such as low-temperature fuel cells can be helpful in optimizing such systems. In hydrogen-bonded networks, protons transport by both vehicular and structural diffusion. In particular, structural diffusion which involves the making and breaking of covalent bonds is difficult to model efficiently in large-scale atomistic simulations.

We present here a model for simulating proton structural diffusion in molecular dynamics codes. The model uses charge-equilibration techniques to better describe behavior in heterogeneous environments. The quantum aspects of making and breaking covalent bonds are treated with an empirical valence bond (EVB) approach combined with the principles of Car-Parrinello molecular dynamics. This work demonstrates the nature of collective proton conduction in water under different conditions. Future optimization and improvement of the model are also discussed.