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 new first-principles-based polarizable model for water. The model is adapted for simulating proton structural diffusion within molecular dynamics. The model employs charge-equilibration techniques, including an sp-basis parameterization to represent in- and out-of-plane polarization, to describe dynamic electrical response to heterogeneous environments. The quantum aspects of electron correlation and of making and breaking covalent bonds are treated with additional potential expressions. This work demonstrates the nature of collective proton conduction in water under different conditions. Future optimization and improvement of the model are also discussed.