The mechanisms and temperature dependence of proton transfer in ice were studied using molecular dynamics simulations in the temperature range of 100-265 K. Our results show the mobility of the excess proton on the surface of ice Ih and the surface of amorphous ice decreases with temperature, with the protons becoming essentially frozen at temperatures below 200 K. The calculated self-diffusion coefficients associated with the excess proton mobility are similar for both surfaces, indicating that the molecular mechanisms are also similar. Importantly, the mobility of excess protons in bulk ice Ih at 190 K is larger than in bulk water at room temperature. While the highly-connected, tetrahedral hydrogen bond network in bulk ice prevents the formation of long-lived Zundel or Eigen configurations, the disordered ice surface stabilizes the excess proton. Consequently, the observed fast proton mobility is due to the high connectivity of the hydrogen bond network of bulk ice.

Fast and slow proton transfer in ice:   The role of the quasi-liquid layer and hydrogen bond network

243rd National Meeting (2012)

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